frankenRFC723x_msg.txt   draft-ietf-httpbis-messaging-19.txt 
Internet Engineering Task Force (IETF) R. Fielding, Ed. HTTP Working Group R. Fielding, Ed.
Request for Comments: 7230 Adobe Internet-Draft Adobe
Obsoletes: 2145, 2616 J. Reschke, Ed. Obsoletes: 7230 (if approved) M. Nottingham, Ed.
Updates: 2817, 2818 greenbytes Intended status: Standards Track Fastly
Category: Standards Track June 2014 Expires: 14 March 2022 J. Reschke, Ed.
ISSN: 2070-1721 greenbytes
10 September 2021
Hypertext Transfer Protocol (HTTP/1.1): Message Syntax and Routing HTTP/1.1
draft-ietf-httpbis-messaging-19
Abstract Abstract
The Hypertext Transfer Protocol (HTTP) is a stateless application- The Hypertext Transfer Protocol (HTTP) is a stateless application-
level protocol for distributed, collaborative, hypertext information level protocol for distributed, collaborative, hypertext information
systems. This document provides an overview of HTTP architecture and systems. This document specifies the HTTP/1.1 message syntax,
its associated terminology, defines the "http" and "https" Uniform message parsing, connection management, and related security
Resource Identifier (URI) schemes, defines the HTTP/1.1 message concerns.
syntax and parsing requirements, and describes related security
concerns for implementations. This document obsoletes portions of RFC 7230.
Editorial Note Editorial Note
This note is not in the original RFC. This note is to be removed before publishing as an RFC.
The purpose of this document is to produce diffs that show just the Discussion of this draft takes place on the HTTP working group
changes from text in the original RFCs that were input for http-core. mailing list (ietf-http-wg@w3.org), which is archived at
Hence, the frankenRFC documents show all of the original text (including <https://lists.w3.org/Archives/Public/ietf-http-wg/>.
stuff that has been deleted) plus some new text [in brackets] to anchor
context, rearranged to minimize the resulting diffs when compared to the
most recently published version of draft-ietf-httpbis-messaging.
After this document is updated to match any reorg changes in the latest Working Group information can be found at <https://httpwg.org/>;
version, the franken diffs are saved and published in this directory as source code and issues list for this draft can be found at
diff_messaging_frfc_to_NN.html (where NN is the I-D draft revision) <https://github.com/httpwg/http-core>.
The changes in this draft are summarized in Appendix D.20.
Status of This Memo Status of This Memo
This is an Internet Standards Track document. This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
This document is a product of the Internet Engineering Task Force Internet-Drafts are working documents of the Internet Engineering
(IETF). It represents the consensus of the IETF community. It has Task Force (IETF). Note that other groups may also distribute
received public review and has been approved for publication by the working documents as Internet-Drafts. The list of current Internet-
Internet Engineering Steering Group (IESG). Further information on Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata, Internet-Drafts are draft documents valid for a maximum of six months
and how to provide feedback on it may be obtained at and may be updated, replaced, or obsoleted by other documents at any
http://www.rfc-editor.org/info/rfc7230. time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 14 March 2022.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction ....................................................5 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Requirements Notation ......................................6 1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 5
1.2. Syntax Notation ............................................6 1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 5
2. Architecture ....................................................6 2. Message . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Client/Server Messaging ....................................7 2.1. Message Format . . . . . . . . . . . . . . . . . . . . . 6
2.2. Implementation Diversity ...................................8 2.2. Message Parsing . . . . . . . . . . . . . . . . . . . . . 7
2.3. Intermediaries .............................................9 2.3. HTTP Version . . . . . . . . . . . . . . . . . . . . . . 8
2.4. Caches ....................................................11 3. Request Line . . . . . . . . . . . . . . . . . . . . . . . . 9
2.5. Conformance and Error Handling ............................12 3.1. Method . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.6. Protocol Versioning .......................................13 3.2. Request Target . . . . . . . . . . . . . . . . . . . . . 10
2.7. Uniform Resource Identifiers ..............................16 3.2.1. origin-form . . . . . . . . . . . . . . . . . . . . . 11
2.7.1. http URI Scheme ....................................17 3.2.2. absolute-form . . . . . . . . . . . . . . . . . . . . 11
2.7.2. https URI Scheme ...................................18 3.2.3. authority-form . . . . . . . . . . . . . . . . . . . 12
2.7.3. http and https URI Normalization and Comparison ....19 3.2.4. asterisk-form . . . . . . . . . . . . . . . . . . . . 12
3. Message Format .................................................19 3.3. Reconstructing the Target URI . . . . . . . . . . . . . . 13
3.1. Start Line ................................................20 4. Status Line . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.1.1. Request Line .......................................21 5. Field Syntax . . . . . . . . . . . . . . . . . . . . . . . . 16
3.1.2. Status Line ........................................22 5.1. Field Line Parsing . . . . . . . . . . . . . . . . . . . 16
3.2. Header Fields .............................................22 5.2. Obsolete Line Folding . . . . . . . . . . . . . . . . . . 17
3.2.1. Field Extensibility ................................23 6. Message Body . . . . . . . . . . . . . . . . . . . . . . . . 17
3.2.2. Field Order ........................................23 6.1. Transfer-Encoding . . . . . . . . . . . . . . . . . . . . 18
3.2.3. Whitespace .........................................24 6.2. Content-Length . . . . . . . . . . . . . . . . . . . . . 20
3.2.4. Field Parsing ......................................25 6.3. Message Body Length . . . . . . . . . . . . . . . . . . . 20
3.2.5. Field Limits .......................................26 7. Transfer Codings . . . . . . . . . . . . . . . . . . . . . . 23
3.2.6. Field Value Components .............................27 7.1. Chunked Transfer Coding . . . . . . . . . . . . . . . . . 23
3.3. Message Body ..............................................28 7.1.1. Chunk Extensions . . . . . . . . . . . . . . . . . . 24
3.3.1. Transfer-Encoding ..................................28 7.1.2. Chunked Trailer Section . . . . . . . . . . . . . . . 25
3.3.2. Content-Length .....................................30 7.1.3. Decoding Chunked . . . . . . . . . . . . . . . . . . 25
3.3.3. Message Body Length ................................32 7.2. Transfer Codings for Compression . . . . . . . . . . . . 26
3.4. Handling Incomplete Messages ..............................34 7.3. Transfer Coding Registry . . . . . . . . . . . . . . . . 26
3.5. Message Parsing Robustness ................................34 7.4. Negotiating Transfer Codings . . . . . . . . . . . . . . 27
4. Transfer Codings ...............................................35 8. Handling Incomplete Messages . . . . . . . . . . . . . . . . 28
4.1. Chunked Transfer Coding ...................................36 9. Connection Management . . . . . . . . . . . . . . . . . . . . 29
4.1.1. Chunk Extensions ...................................36 9.1. Establishment . . . . . . . . . . . . . . . . . . . . . . 29
4.1.2. Chunked Trailer Part ...............................37 9.2. Associating a Response to a Request . . . . . . . . . . . 29
4.1.3. Decoding Chunked ...................................38 9.3. Persistence . . . . . . . . . . . . . . . . . . . . . . . 30
4.2. Compression Codings .......................................38 9.3.1. Retrying Requests . . . . . . . . . . . . . . . . . . 31
4.2.1. Compress Coding ....................................38 9.3.2. Pipelining . . . . . . . . . . . . . . . . . . . . . 31
4.2.2. Deflate Coding .....................................38 9.4. Concurrency . . . . . . . . . . . . . . . . . . . . . . . 32
4.2.3. Gzip Coding ........................................39 9.5. Failures and Timeouts . . . . . . . . . . . . . . . . . . 32
4.3. TE ........................................................39 9.6. Tear-down . . . . . . . . . . . . . . . . . . . . . . . . 33
4.4. Trailer ...................................................40 9.7. TLS Connection Initiation . . . . . . . . . . . . . . . . 35
5. Message Routing ................................................40 9.8. TLS Connection Closure . . . . . . . . . . . . . . . . . 35
5.1. Identifying a Target Resource .............................40 10. Enclosing Messages as Data . . . . . . . . . . . . . . . . . 36
5.2. Connecting Inbound ........................................41 10.1. Media Type message/http . . . . . . . . . . . . . . . . 36
5.3. Request Target ............................................41 10.2. Media Type application/http . . . . . . . . . . . . . . 37
5.3.1. origin-form ........................................42 11. Security Considerations . . . . . . . . . . . . . . . . . . . 38
5.3.2. absolute-form ......................................42 11.1. Response Splitting . . . . . . . . . . . . . . . . . . . 38
5.3.3. authority-form .....................................43 11.2. Request Smuggling . . . . . . . . . . . . . . . . . . . 39
5.3.4. asterisk-form ......................................43 11.3. Message Integrity . . . . . . . . . . . . . . . . . . . 40
5.4. Host ......................................................44 11.4. Message Confidentiality . . . . . . . . . . . . . . . . 40
5.5. Effective Request URI .....................................45 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41
5.6. Associating a Response to a Request .......................46 12.1. Field Name Registration . . . . . . . . . . . . . . . . 41
5.7. Message Forwarding ........................................47 12.2. Media Type Registration . . . . . . . . . . . . . . . . 41
5.7.1. Via ................................................47 12.3. Transfer Coding Registration . . . . . . . . . . . . . . 41
5.7.2. Transformations ....................................49 12.4. ALPN Protocol ID Registration . . . . . . . . . . . . . 42
6. Connection Management ..........................................50 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 43
6.1. Connection ................................................51 13.1. Normative References . . . . . . . . . . . . . . . . . . 43
6.2. Establishment .............................................52 13.2. Informative References . . . . . . . . . . . . . . . . . 44
6.3. Persistence ...............................................52 Appendix A. Collected ABNF . . . . . . . . . . . . . . . . . . . 45
6.3.1. Retrying Requests ..................................53 Appendix B. Differences between HTTP and MIME . . . . . . . . . 47
6.3.2. Pipelining .........................................54 B.1. MIME-Version . . . . . . . . . . . . . . . . . . . . . . 47
6.4. Concurrency ...............................................55 B.2. Conversion to Canonical Form . . . . . . . . . . . . . . 47
6.5. Failures and Timeouts .....................................55 B.3. Conversion of Date Formats . . . . . . . . . . . . . . . 48
6.6. Tear-down .................................................56 B.4. Conversion of Content-Encoding . . . . . . . . . . . . . 48
6.7. Upgrade ...................................................57 B.5. Conversion of Content-Transfer-Encoding . . . . . . . . . 48
7. ABNF List Extension: #rule .....................................59 B.6. MHTML and Line Length Limitations . . . . . . . . . . . . 48
8. IANA Considerations ............................................61 Appendix C. Changes from previous RFCs . . . . . . . . . . . . . 49
8.1. Header Field Registration .................................61 C.1. Changes from HTTP/0.9 . . . . . . . . . . . . . . . . . . 49
8.2. URI Scheme Registration ...................................62 C.2. Changes from HTTP/1.0 . . . . . . . . . . . . . . . . . . 49
8.3. Internet Media Type Registration ..........................62 C.2.1. Multihomed Web Servers . . . . . . . . . . . . . . . 49
8.3.1. Internet Media Type message/http ...................62 C.2.2. Keep-Alive Connections . . . . . . . . . . . . . . . 49
8.3.2. Internet Media Type application/http ...............63 C.2.3. Introduction of Transfer-Encoding . . . . . . . . . . 50
8.4. Transfer Coding Registry ..................................64 C.3. Changes from RFC 7230 . . . . . . . . . . . . . . . . . . 50
8.4.1. Procedure ..........................................65 Appendix D. Change Log . . . . . . . . . . . . . . . . . . . . . 51
8.4.2. Registration .......................................65 D.1. Between RFC7230 and draft 00 . . . . . . . . . . . . . . 51
8.5. Content Coding Registration ...............................66 D.2. Since draft-ietf-httpbis-messaging-00 . . . . . . . . . . 51
8.6. Upgrade Token Registry ....................................66 D.3. Since draft-ietf-httpbis-messaging-01 . . . . . . . . . . 52
8.6.1. Procedure ..........................................66 D.4. Since draft-ietf-httpbis-messaging-02 . . . . . . . . . . 52
8.6.2. Upgrade Token Registration .........................67 D.5. Since draft-ietf-httpbis-messaging-03 . . . . . . . . . . 53
9. Security Considerations ........................................67 D.6. Since draft-ietf-httpbis-messaging-04 . . . . . . . . . . 53
9.1. Establishing Authority ....................................67 D.7. Since draft-ietf-httpbis-messaging-05 . . . . . . . . . . 53
9.2. Risks of Intermediaries ...................................68 D.8. Since draft-ietf-httpbis-messaging-06 . . . . . . . . . . 54
9.3. Attacks via Protocol Element Length .......................69 D.9. Since draft-ietf-httpbis-messaging-07 . . . . . . . . . . 54
9.4. Response Splitting ........................................69 D.10. Since draft-ietf-httpbis-messaging-08 . . . . . . . . . . 54
9.5. Request Smuggling .........................................70 D.11. Since draft-ietf-httpbis-messaging-09 . . . . . . . . . . 55
9.6. Message Integrity .........................................70 D.12. Since draft-ietf-httpbis-messaging-10 . . . . . . . . . . 55
9.7. Message Confidentiality ...................................71 D.13. Since draft-ietf-httpbis-messaging-11 . . . . . . . . . . 55
9.8. Privacy of Server Log Information .........................71 D.14. Since draft-ietf-httpbis-messaging-12 . . . . . . . . . . 55
10. Acknowledgments ...............................................72 D.15. Since draft-ietf-httpbis-messaging-13 . . . . . . . . . . 56
11. References ....................................................74 D.16. Since draft-ietf-httpbis-messaging-14 . . . . . . . . . . 56
11.1. Normative References .....................................74 D.17. Since draft-ietf-httpbis-messaging-15 . . . . . . . . . . 57
11.2. Informative References ...................................75 D.18. Since draft-ietf-httpbis-messaging-16 . . . . . . . . . . 57
Appendix A. HTTP Version History ..................................78 D.19. Since draft-ietf-httpbis-messaging-17 . . . . . . . . . . 57
A.1. Changes from HTTP/1.0 ....................................78 D.20. Since draft-ietf-httpbis-messaging-18 . . . . . . . . . . 57
A.1.1. Multihomed Web Servers ............................78 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 58
A.1.2. Keep-Alive Connections ............................79 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
A.1.3. Introduction of Transfer-Encoding .................79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 60
A.2. Changes from RFC 2616 ....................................80
Appendix B. Collected ABNF ........................................82
Index .............................................................85
1. Introduction 1. Introduction
The Hypertext Transfer Protocol (HTTP) is a stateless application- The Hypertext Transfer Protocol (HTTP) is a stateless application-
level request/response protocol that uses extensible semantics and level request/response protocol that uses extensible semantics and
self-descriptive message payloads for flexible interaction with self-descriptive messages for flexible interaction with network-based
network-based hypertext information systems. This document is the hypertext information systems. HTTP/1.1 is defined by:
first in a series of documents that collectively form the HTTP/1.1
specification:
1. "Message Syntax and Routing" (this document)
2. "Semantics and Content" [RFC7231]
3. "Conditional Requests" [RFC7232]
4. "Range Requests" [RFC7233]
5. "Caching" [RFC7234] * This document
6. "Authentication" [RFC7235] * "HTTP Semantics" [HTTP]
* "HTTP Caching" [CACHING]
This HTTP/1.1 specification obsoletes RFC 2616 and RFC 2145 (on HTTP This document specifies how HTTP semantics are conveyed using the
versioning). This specification also updates the use of CONNECT to HTTP/1.1 message syntax, framing and connection management
establish a tunnel, previously defined in RFC 2817, and defines the mechanisms. Its goal is to define the complete set of requirements
"https" URI scheme that was described informally in RFC 2818. for HTTP/1.1 message parsers and message-forwarding intermediaries.
This document describes the architectural elements that are used or This document obsoletes the portions of RFC 7230 related to HTTP/1.1
referred to in HTTP, defines the "http" and "https" URI schemes, messaging and connection management, with the changes being
describes overall network operation and connection management, and summarized in Appendix C.3. The other parts of RFC 7230 are
defines HTTP message framing and forwarding requirements. Our goal obsoleted by "HTTP Semantics" [HTTP].
is to define all of the mechanisms necessary for HTTP message
handling that are independent of message semantics, thereby defining
the complete set of requirements for message parsers and message-
forwarding intermediaries.
1.1. Requirements Notation 1.1. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in [RFC2119]. "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Conformance criteria and considerations regarding error handling are Conformance criteria and considerations regarding error handling are
defined in Section 2.5. defined in Section 2 of [HTTP].
1.2. Syntax Notation 1.2. Syntax Notation
This specification uses the Augmented Backus-Naur Form (ABNF) This specification uses the Augmented Backus-Naur Form (ABNF)
notation of [RFC5234] with a list extension, defined in Section 7, notation of [RFC5234], extended with the notation for case-
sensitivity in strings defined in [RFC7405].
It also uses a list extension, defined in Section 5.6.1 of [HTTP],
that allows for compact definition of comma-separated lists using a that allows for compact definition of comma-separated lists using a
'#' operator (similar to how the '*' operator indicates repetition). '#' operator (similar to how the '*' operator indicates repetition).
Appendix B shows the collected grammar with all list operators Appendix A shows the collected grammar with all list operators
expanded to standard ABNF notation. expanded to standard ABNF notation.
As a convention, ABNF rule names prefixed with "obs-" denote As a convention, ABNF rule names prefixed with "obs-" denote
"obsolete" grammar rules that appear for historical reasons. "obsolete" grammar rules that appear for historical reasons.
The following core rules are included by reference, as defined in The following core rules are included by reference, as defined in
[RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF [RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF
(CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote), (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote),
HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line
feed), OCTET (any 8-bit sequence of data), SP (space), and VCHAR (any feed), OCTET (any 8-bit sequence of data), SP (space), and VCHAR (any
visible [USASCII] character). visible [USASCII] character).
The rules below are defined in [RFC7230]: The rules below are defined in [HTTP]:
BWS = <BWS, see [RFC7230], Section 3.2.3> BWS = <BWS, see [HTTP], Section 5.6.3>
OWS = <OWS, see [RFC7230], Section 3.2.3> OWS = <OWS, see [HTTP], Section 5.6.3>
RWS = <RWS, see [RFC7230], Section 3.2.3> RWS = <RWS, see [HTTP], Section 5.6.3>
comment = <comment, see [RFC7230], Section 3.2.6> absolute-path = <absolute-path, see [HTTP], Section 4.1>
field-name = <comment, see [RFC7230], Section 3.2> field-name = <field-name, see [HTTP], Section 5.1>
quoted-string = <quoted-string, see [RFC7230], Section 3.2.6> field-value = <field-value, see [HTTP], Section 5.5>
token = <token, see [RFC7230], Section 3.2.6> obs-text = <obs-text, see [HTTP], Section 5.6.4>
quoted-string = <quoted-string, see [HTTP], Section 5.6.4>
token = <token, see [HTTP], Section 5.6.2>
transfer-coding =
<transfer-coding, see [HTTP], Section 10.1.4>
[new] The rules below are defined in [URI]:
absolute-URI = <absolute-URI, see [RFC7230], Section 2.7> absolute-URI = <absolute-URI, see [URI], Section 4.3>
partial-URI = <partial-URI, see [RFC7230], Section 2.7> authority = <authority, see [URI], Section 3.2>
URI-reference = <URI-reference, see [RFC7230], Section 2.7> uri-host = <host, see [URI], Section 3.2.2>
port = <port, see [URI], Section 3.2.3>
query = <query, see [URI], Section 3.4>
2. Message 2. Message
HTTP/1.1 clients and servers communicate by sending messages. See
Section 3 of [HTTP] for the general terminology and core concepts of
HTTP.
2.1. Message Format 2.1. Message Format
All HTTP/1.1 messages consist of a start-line followed by a sequence An HTTP/1.1 message consists of a start-line followed by a CRLF and a
of octets in a format similar to the Internet Message Format sequence of octets in a format similar to the Internet Message Format
[RFC5322]: zero or more header fields (collectively referred to as [RFC5322]: zero or more header field lines (collectively referred to
the "headers" or the "header section"), an empty line indicating the as the "headers" or the "header section"), an empty line indicating
end of the header section, and an optional message body. the end of the header section, and an optional message body.
HTTP-message = start-line HTTP-message = start-line CRLF
*( header-field CRLF ) *( field-line CRLF )
CRLF CRLF
[ message-body ] [ message-body ]
3.1. Start Line A message can be either a request from client to server or a response
from server to client. Syntactically, the two types of message
An HTTP message can be either a request from client to server or a differ only in the start-line, which is either a request-line (for
response from server to client. Syntactically, the two types of requests) or a status-line (for responses), and in the algorithm for
message differ only in the start-line, which is either a request-line determining the length of the message body (Section 6).
(for requests) or a status-line (for responses), and in the algorithm
for determining the length of the message body (Section 3.3).
start-line = request-line / status-line start-line = request-line / status-line
In theory, a client could receive requests and a server could receive In theory, a client could receive requests and a server could receive
responses, distinguishing them by their different start-line formats, responses, distinguishing them by their different start-line formats.
but, in practice, servers are implemented to only expect a request (a In practice, servers are implemented to only expect a request (a
response is interpreted as an unknown or invalid request method) and response is interpreted as an unknown or invalid request method) and
clients are implemented to only expect a response. clients are implemented to only expect a response.
Messages are passed in a format similar to that used by Internet mail HTTP makes use of some protocol elements similar to the Multipurpose
[RFC5322] and the Internet Mail Extensions (MIME) [RFC2045]. See Appendix B for the
Multipurpose Internet Mail Extensions (MIME) [RFC2045] (see Appendix A differences between HTTP and MIME messages.
of [RFC7231] for the differences between HTTP and MIME messages).
2.2. Message Parsing Robustness 2.2. Message Parsing
The normal procedure for parsing an HTTP message is to read the The normal procedure for parsing an HTTP message is to read the
start-line into a structure, read each header field into a hash table start-line into a structure, read each header field line into a hash
by field name until the empty line, and then use the parsed data to table by field name until the empty line, and then use the parsed
determine if a message body is expected. If a message body has been data to determine if a message body is expected. If a message body
indicated, then it is read as a stream until an amount of octets has been indicated, then it is read as a stream until an amount of
equal to the message body length is read or the connection is closed. octets equal to the message body length is read or the connection is
closed.
A recipient MUST parse an HTTP message as a sequence of octets in an A recipient MUST parse an HTTP message as a sequence of octets in an
encoding that is a superset of US-ASCII [USASCII]. Parsing an HTTP encoding that is a superset of US-ASCII [USASCII]. Parsing an HTTP
message as a stream of Unicode characters, without regard for the message as a stream of Unicode characters, without regard for the
specific encoding, creates security vulnerabilities due to the specific encoding, creates security vulnerabilities due to the
varying ways that string processing libraries handle invalid varying ways that string processing libraries handle invalid
multibyte character sequences that contain the octet LF (%x0A). multibyte character sequences that contain the octet LF (%x0A).
String-based parsers can only be safely used within protocol elements String-based parsers can only be safely used within protocol elements
after the element has been extracted from the message, such as within after the element has been extracted from the message, such as within
a header field-value after message parsing has delineated the a header field line value after message parsing has delineated the
individual fields. individual field lines.
Although the line terminator for the start-line and header fields is Although the line terminator for the start-line and fields is the
the sequence CRLF, a recipient MAY recognize a single LF as a line sequence CRLF, a recipient MAY recognize a single LF as a line
terminator and ignore any preceding CR. terminator and ignore any preceding CR.
A sender MUST NOT generate a bare CR (a CR character not immediately
followed by LF) within any protocol elements other than the content.
A recipient of such a bare CR MUST consider that element to be
invalid or replace each bare CR with SP before processing the element
or forwarding the message.
Older HTTP/1.0 user agent implementations might send an extra CRLF Older HTTP/1.0 user agent implementations might send an extra CRLF
after a POST request as a workaround for some early server after a POST request as a workaround for some early server
applications that failed to read message body content that was not applications that failed to read message body content that was not
terminated by a line-ending. An HTTP/1.1 user agent MUST NOT preface terminated by a line-ending. An HTTP/1.1 user agent MUST NOT preface
or follow a request with an extra CRLF. If terminating the request or follow a request with an extra CRLF. If terminating the request
message body with a line-ending is desired, then the user agent MUST message body with a line-ending is desired, then the user agent MUST
count the terminating CRLF octets as part of the message body length. count the terminating CRLF octets as part of the message body length.
In the interest of robustness, a server that is expecting to receive In the interest of robustness, a server that is expecting to receive
and parse a request-line SHOULD ignore at least one empty line (CRLF) and parse a request-line SHOULD ignore at least one empty line (CRLF)
received prior to the request-line. received prior to the request-line.
A sender MUST NOT send whitespace between the start-line and the A sender MUST NOT send whitespace between the start-line and the
first header field. A recipient that receives whitespace between the first header field.
start-line and the first header field MUST either reject the message
as invalid or consume each whitespace-preceded line without further
processing of it (i.e., ignore the entire line, along with any
subsequent lines preceded by whitespace, until a properly formed
header field is received or the header section is terminated).
The presence of such whitespace in a request might be an attempt to A recipient that receives whitespace between the start-line and the
trick a server into ignoring that field or processing the line after first header field MUST either reject the message as invalid or
it as a new request, either of which might result in a security consume each whitespace-preceded line without further processing of
vulnerability if other implementations within the request chain it (i.e., ignore the entire line, along with any subsequent lines
interpret the same message differently. Likewise, the presence of preceded by whitespace, until a properly formed header field is
such whitespace in a response might be ignored by some clients or received or the header section is terminated). Rejection or removal
cause others to cease parsing. of invalid whitespace-preceded lines is necessary to prevent their
misinterpretation by downstream recipients that might be vulnerable
to request smuggling (Section 11.2) or response splitting
(Section 11.1) attacks.
When a server listening only for HTTP request messages, or processing When a server listening only for HTTP request messages, or processing
what appears from the start-line to be an HTTP request message, what appears from the start-line to be an HTTP request message,
receives a sequence of octets that does not match the HTTP-message receives a sequence of octets that does not match the HTTP-message
grammar aside from the robustness exceptions listed above, the server grammar aside from the robustness exceptions listed above, the server
SHOULD respond with a 400 (Bad Request) response. SHOULD respond with a 400 (Bad Request) response and close the
connection.
2.6. Protocol Versioning 2.3. HTTP Version
HTTP uses a "<major>.<minor>" numbering scheme to indicate versions HTTP uses a "<major>.<minor>" numbering scheme to indicate versions
of the protocol. This specification defines version "1.1". of the protocol. This specification defines version "1.1".
Section 2.5 of [HTTP] specifies the semantics of HTTP version
numbers.
The version of an HTTP message is indicated by an HTTP-version field The version of an HTTP/1.x message is indicated by an HTTP-version
in the first line of the message. HTTP-version is case-sensitive. field in the start-line. HTTP-version is case-sensitive.
HTTP-version = HTTP-name "/" DIGIT "." DIGIT HTTP-version = HTTP-name "/" DIGIT "." DIGIT
HTTP-name = %x48.54.54.50 ; "HTTP", case-sensitive HTTP-name = %s"HTTP"
When an HTTP/1.1 message is sent to an HTTP/1.0 recipient [RFC1945] When an HTTP/1.1 message is sent to an HTTP/1.0 recipient [HTTP/1.0]
or a recipient whose version is unknown, the HTTP/1.1 message is or a recipient whose version is unknown, the HTTP/1.1 message is
constructed such that it can be interpreted as a valid HTTP/1.0 constructed such that it can be interpreted as a valid HTTP/1.0
message if all of the newer features are ignored. This specification message if all of the newer features are ignored. This specification
places recipient-version requirements on some new features so that a places recipient-version requirements on some new features so that a
conformant sender will only use compatible features until it has conformant sender will only use compatible features until it has
determined, through configuration or the receipt of a message, that determined, through configuration or the receipt of a message, that
the recipient supports HTTP/1.1. the recipient supports HTTP/1.1.
Intermediaries that process HTTP messages (i.e., all intermediaries Intermediaries that process HTTP messages (i.e., all intermediaries
other than those acting as tunnels) MUST send their own HTTP-version other than those acting as tunnels) MUST send their own HTTP-version
in forwarded messages. In other words, they are not allowed to in forwarded messages, unless it is purposefully downgraded as a
blindly forward the first line of an HTTP message without ensuring workaround for an upstream issue. In other words, an intermediary is
that the protocol version in that message matches a version to which not allowed to blindly forward the start-line without ensuring that
that intermediary is conformant for both the receiving and sending of the protocol version in that message matches a version to which that
messages. Forwarding an HTTP message without rewriting the intermediary is conformant for both the receiving and sending of
HTTP-version might result in communication errors when downstream messages. Forwarding an HTTP message without rewriting the HTTP-
version might result in communication errors when downstream
recipients use the message sender's version to determine what recipients use the message sender's version to determine what
features are safe to use for later communication with that sender. features are safe to use for later communication with that sender.
A server MAY send an HTTP/1.0 response to a request if it is known or A server MAY send an HTTP/1.0 response to an HTTP/1.1 request if it
suspected that the client incorrectly implements the HTTP is known or suspected that the client incorrectly implements the HTTP
specification and is incapable of correctly processing later version specification and is incapable of correctly processing later version
responses, such as when a client fails to parse the version number responses, such as when a client fails to parse the version number
correctly or when an intermediary is known to blindly forward the correctly or when an intermediary is known to blindly forward the
HTTP-version even when it doesn't conform to the given minor version HTTP-version even when it doesn't conform to the given minor version
of the protocol. Such protocol downgrades SHOULD NOT be performed of the protocol. Such protocol downgrades SHOULD NOT be performed
unless triggered by specific client attributes, such as when one or unless triggered by specific client attributes, such as when one or
more of the request header fields (e.g., User-Agent) uniquely match more of the request header fields (e.g., User-Agent) uniquely match
the values sent by a client known to be in error. the values sent by a client known to be in error.
3.1.1. Request Line 3. Request Line
A request-line begins with a method token, followed by a single space A request-line begins with a method token, followed by a single space
(SP), the request-target, another single space (SP), the protocol (SP), the request-target, another single space (SP), and ends with
version, and ends with CRLF. the protocol version.
request-line = method SP request-target SP HTTP-version CRLF request-line = method SP request-target SP HTTP-version
Although the request-line and status-line grammar rules require that Although the request-line grammar rule requires that each of the
each of the component elements be separated by a single SP octet, component elements be separated by a single SP octet, recipients MAY
recipients MAY instead parse on whitespace-delimited word boundaries instead parse on whitespace-delimited word boundaries and, aside from
and, aside from the CRLF terminator, treat any form of whitespace as the CRLF terminator, treat any form of whitespace as the SP separator
the SP separator while ignoring preceding or trailing whitespace; while ignoring preceding or trailing whitespace; such whitespace
such whitespace includes one or more of the following octets: SP, includes one or more of the following octets: SP, HTAB, VT (%x0B), FF
HTAB, VT (%x0B), FF (%x0C), or bare CR. However, lenient parsing can (%x0C), or bare CR. However, lenient parsing can result in request
result in security vulnerabilities if there are multiple recipients smuggling security vulnerabilities if there are multiple recipients
of the message and each has its own unique interpretation of of the message and each has its own unique interpretation of
robustness (see Section 9.5). robustness (see Section 11.2).
HTTP does not place a predefined limit on the length of a HTTP does not place a predefined limit on the length of a request-
request-line, as described in Section 2.5. A server that receives a line, as described in Section 2.3 of [HTTP]. A server that receives
method longer than any that it implements SHOULD respond with a 501 a method longer than any that it implements SHOULD respond with a 501
(Not Implemented) status code. A server that receives a (Not Implemented) status code. A server that receives a request-
request-target longer than any URI it wishes to parse MUST respond target longer than any URI it wishes to parse MUST respond with a 414
with a 414 (URI Too Long) status code (see Section 6.5.12 of (URI Too Long) status code (see Section 15.5.15 of [HTTP]).
[RFC7231]).
Various ad hoc limitations on request-line length are found in Various ad hoc limitations on request-line length are found in
practice. It is RECOMMENDED that all HTTP senders and recipients practice. It is RECOMMENDED that all HTTP senders and recipients
support, at a minimum, request-line lengths of 8000 octets. support, at a minimum, request-line lengths of 8000 octets.
3.1. Method
The method token indicates the request method to be performed on the The method token indicates the request method to be performed on the
target resource. The request method is case-sensitive. target resource. The request method is case-sensitive.
method = token method = token
The request methods defined by this specification can be found in The request methods defined by this specification can be found in
Section 4 of [RFC7231], along with information regarding the HTTP Section 9 of [HTTP], along with information regarding the HTTP method
method registry and considerations for defining new methods. registry and considerations for defining new methods.
3.2. Request Target 3.2. Request Target
The request-target identifies the target resource upon which to apply The request-target identifies the target resource upon which to apply
the request, as defined in Section 5.3. the request. The client derives a request-target from its desired
Once an inbound connection is obtained, the client sends an HTTP
request message (Section 3) with a request-target derived from the
target URI. There are four distinct formats for the request-target, target URI. There are four distinct formats for the request-target,
depending on both the method being requested and whether the request depending on both the method being requested and whether the request
is to a proxy. is to a proxy.
request-target = origin-form request-target = origin-form
/ absolute-form / absolute-form
/ authority-form / authority-form
/ asterisk-form / asterisk-form
Recipients typically parse the request-line into its component parts No whitespace is allowed in the request-target. Unfortunately, some
by splitting on whitespace (see Section 3.5), since no whitespace is user agents fail to properly encode or exclude whitespace found in
allowed in the three components. Unfortunately, some user agents hypertext references, resulting in those disallowed characters being
fail to properly encode or exclude whitespace found in hypertext sent as the request-target in a malformed request-line.
references, resulting in those disallowed characters being sent in a
request-target.
Recipients of an invalid request-line SHOULD respond with either a Recipients of an invalid request-line SHOULD respond with either a
400 (Bad Request) error or a 301 (Moved Permanently) redirect with 400 (Bad Request) error or a 301 (Moved Permanently) redirect with
the request-target properly encoded. A recipient SHOULD NOT attempt the request-target properly encoded. A recipient SHOULD NOT attempt
to autocorrect and then process the request without a redirect, since to autocorrect and then process the request without a redirect, since
the invalid request-line might be deliberately crafted to bypass the invalid request-line might be deliberately crafted to bypass
security filters along the request chain. security filters along the request chain.
A client MUST send a Host header field in all HTTP/1.1 request A client MUST send a Host header field (Section 7.2 of [HTTP]) in all
messages. If the target URI includes an authority component, then a HTTP/1.1 request messages. If the target URI includes an authority
client MUST send a field-value for Host that is identical to that component, then a client MUST send a field value for Host that is
authority component, excluding any userinfo subcomponent and its "@" identical to that authority component, excluding any userinfo
delimiter (Section 2.7.1). If the authority component is missing or subcomponent and its "@" delimiter (Section 4.2.1 of [HTTP]). If the
undefined for the target URI, then a client MUST send a Host header authority component is missing or undefined for the target URI, then
field with an empty field-value. a client MUST send a Host header field with an empty field value.
A server MUST respond with a 400 (Bad Request) status code to any A server MUST respond with a 400 (Bad Request) status code to any
HTTP/1.1 request message that lacks a Host header field and to any HTTP/1.1 request message that lacks a Host header field and to any
request message that contains more than one Host header field or a request message that contains more than one Host header field line or
Host header field with an invalid field-value. a Host header field with an invalid field value.
3.2.1. origin-form 3.2.1. origin-form
The most common form of request-target is the origin-form. The most common form of request-target is the _origin-form_.
origin-form = absolute-path [ "?" query ] origin-form = absolute-path [ "?" query ]
When making a request directly to an origin server, other than a When making a request directly to an origin server, other than a
CONNECT or server-wide OPTIONS request (as detailed below), a client CONNECT or server-wide OPTIONS request (as detailed below), a client
MUST send only the absolute path and query components of the target MUST send only the absolute path and query components of the target
URI as the request-target. If the target URI's path component is URI as the request-target. If the target URI's path component is
empty, the client MUST send "/" as the path within the origin-form of empty, the client MUST send "/" as the path within the origin-form of
request-target. A Host header field is also sent, as defined in request-target. A Host header field is also sent, as defined in
Section 5.4. Section 7.2 of [HTTP].
For example, a client wishing to retrieve a representation of the For example, a client wishing to retrieve a representation of the
resource identified as resource identified as
http://www.example.org/where?q=now http://www.example.org/where?q=now
directly from the origin server would open (or reuse) a TCP directly from the origin server would open (or reuse) a TCP
connection to port 80 of the host "www.example.org" and send the connection to port 80 of the host "www.example.org" and send the
lines: lines:
GET /where?q=now HTTP/1.1 GET /where?q=now HTTP/1.1
Host: www.example.org Host: www.example.org
followed by the remainder of the request message. followed by the remainder of the request message.
3.2.2. absolute-form 3.2.2. absolute-form
When making a request to a proxy, other than a CONNECT or server-wide When making a request to a proxy, other than a CONNECT or server-wide
OPTIONS request (as detailed below), a client MUST send the target OPTIONS request (as detailed below), a client MUST send the target
URI in absolute-form as the request-target. URI in _absolute-form_ as the request-target.
absolute-form = absolute-URI absolute-form = absolute-URI
The proxy is requested to either service that request from a valid The proxy is requested to either service that request from a valid
cache, if possible, or make the same request on the client's behalf cache, if possible, or make the same request on the client's behalf
to either the next inbound proxy server or directly to the origin to either the next inbound proxy server or directly to the origin
server indicated by the request-target. Requirements on such server indicated by the request-target. Requirements on such
"forwarding" of messages are defined in Section 5.7. "forwarding" of messages are defined in Section 7.6 of [HTTP].
An example absolute-form of request-line would be: An example absolute-form of request-line would be:
GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1 GET http://www.example.org/pub/WWW/TheProject.html HTTP/1.1
A client MUST send a Host header field in an HTTP/1.1 request even if A client MUST send a Host header field in an HTTP/1.1 request even if
the request-target is in the absolute-form, since this allows the the request-target is in the absolute-form, since this allows the
Host information to be forwarded through ancient HTTP/1.0 proxies Host information to be forwarded through ancient HTTP/1.0 proxies
that might not have implemented Host. that might not have implemented Host.
When a proxy receives a request with an absolute-form of When a proxy receives a request with an absolute-form of request-
request-target, the proxy MUST ignore the received Host header field target, the proxy MUST ignore the received Host header field (if any)
(if any) and instead replace it with the host information of the and instead replace it with the host information of the request-
request-target. A proxy that forwards such a request MUST generate a target. A proxy that forwards such a request MUST generate a new
new Host field-value based on the received request-target rather than Host field value based on the received request-target rather than
forward the received Host field-value. forward the received Host field value.
To allow for transition to the absolute-form for all requests in some When an origin server receives a request with an absolute-form of
future version of HTTP, a server MUST accept the absolute-form in request-target, the origin server MUST ignore the received Host
requests, even though HTTP/1.1 clients will only send them in header field (if any) and instead use the host information of the
requests to proxies. request-target. Note that if the request-target does not have an
authority component, an empty Host header field will be sent in this
case.
A server MUST accept the absolute-form in requests even though most
HTTP/1.1 clients will only send the absolute-form to a proxy.
3.2.3. authority-form 3.2.3. authority-form
The authority-form of request-target is only used for CONNECT The _authority-form_ of request-target is only used for CONNECT
requests (Section 4.3.6 of [RFC7231]). requests (Section 9.3.6 of [HTTP]). It consists of only the uri-host
and port number of the tunnel destination, separated by a colon
(":").
authority-form = authority authority-form = uri-host ":" port
When making a CONNECT request to establish a tunnel through one or When making a CONNECT request to establish a tunnel through one or
more proxies, a client MUST send only the target URI's authority more proxies, a client MUST send only the host and port of the tunnel
component (excluding any userinfo and its "@" delimiter) as the destination as the request-target. The client obtains the host and
request-target. For example, port from the target URI's authority component, except that it sends
the scheme's default port if the target URI elides the port. For
example, a CONNECT request to "http://www.example.com" looks like
CONNECT www.example.com:80 HTTP/1.1 CONNECT www.example.com:80 HTTP/1.1
Host: www.example.com
3.2.4. asterisk-form 3.2.4. asterisk-form
The asterisk-form of request-target is only used for a server-wide The _asterisk-form_ of request-target is only used for a server-wide
OPTIONS request (Section 4.3.7 of [RFC7231]). OPTIONS request (Section 9.3.7 of [HTTP]).
asterisk-form = "*" asterisk-form = "*"
When a client wishes to request OPTIONS for the server as a whole, as When a client wishes to request OPTIONS for the server as a whole, as
opposed to a specific named resource of that server, the client MUST opposed to a specific named resource of that server, the client MUST
send only "*" (%x2A) as the request-target. For example, send only "*" (%x2A) as the request-target. For example,
OPTIONS * HTTP/1.1 OPTIONS * HTTP/1.1
If a proxy receives an OPTIONS request with an absolute-form of If a proxy receives an OPTIONS request with an absolute-form of
request-target in which the URI has an empty path and no query request-target in which the URI has an empty path and no query
component, then the last proxy on the request chain MUST send a component, then the last proxy on the request chain MUST send a
request-target of "*" when it forwards the request to the indicated request-target of "*" when it forwards the request to the indicated
origin server. origin server.
For example, the request For example, the request
OPTIONS http://www.example.org:8001 HTTP/1.1 OPTIONS http://www.example.org:8001 HTTP/1.1
would be forwarded by the final proxy as would be forwarded by the final proxy as
OPTIONS * HTTP/1.1 OPTIONS * HTTP/1.1
Host: www.example.org:8001 Host: www.example.org:8001
after connecting to port 8001 of host "www.example.org". after connecting to port 8001 of host "www.example.org".
3.5. Effective Request URI 3.3. Reconstructing the Target URI
Since the request-target often contains only part of the user agent's The target URI is the request-target when the request-target is in
target URI, a server reconstructs the intended target as an absolute-form. In that case, a server will parse the URI into its
"effective request URI" to properly service the request. generic components for further evaluation.
If the request-target is in absolute-form, the effective request URI Otherwise, the server reconstructs the target URI from the connection
is the same as the request-target. Otherwise, the effective request context and various parts of the request message in order to identify
URI is constructed as follows: the target resource (Section 7.1 of [HTTP]):
If the server's configuration (or outbound gateway) provides a * If the server's configuration provides for a fixed URI scheme, or
fixed URI scheme, that scheme is used for the effective request a scheme is provided by a trusted outbound gateway, that scheme is
URI. Otherwise, if the request is received over a TLS-secured TCP used for the target URI. This is common in large-scale
connection, the effective request URI's scheme is "https"; if not, deployments because a gateway server will receive the client's
connection context and replace that with their own connection to
the inbound server. Otherwise, if the request is received over a
secured connection, the target URI's scheme is "https"; if not,
the scheme is "http". the scheme is "http".
If the server's configuration (or outbound gateway) provides a * If the request-target is in authority-form, the target URI's
fixed URI authority component, that authority is used for the authority component is the request-target. Otherwise, the target
effective request URI. If not, then if the request-target is in URI's authority component is the field value of the Host header
authority-form, the effective request URI's authority component is field. If there is no Host header field or if its field value is
the same as the request-target. If not, then if a Host header empty or invalid, the target URI's authority component is empty.
field is supplied with a non-empty field-value, the authority
component is the same as the Host field-value. Otherwise, the
authority component is assigned the default name configured for
the server and, if the connection's incoming TCP port number
differs from the default port for the effective request URI's
scheme, then a colon (":") and the incoming port number (in
decimal form) are appended to the authority component.
If the request-target is in authority-form or asterisk-form, the * If the request-target is in authority-form or asterisk-form, the
effective request URI's combined path and query component is target URI's combined path and query component is empty.
empty. Otherwise, the combined path and query component is the Otherwise, the target URI's combined path and query component is
same as the request-target. the request-target.
The components of the effective request URI, once determined as * The components of a reconstructed target URI, once determined as
above, can be combined into absolute-URI form by concatenating the above, can be recombined into absolute-URI form by concatenating
scheme, "://", authority, and combined path and query component. the scheme, "://", authority, and combined path and query
component.
Example 1: the following message received over an insecure TCP Example 1: the following message received over a secure connection
connection
GET /pub/WWW/TheProject.html HTTP/1.1 GET /pub/WWW/TheProject.html HTTP/1.1
Host: www.example.org:8080 Host: www.example.org
has an effective request URI of has a target URI of
http://www.example.org:8080/pub/WWW/TheProject.html https://www.example.org/pub/WWW/TheProject.html
Example 2: the following message received over a TLS-secured TCP Example 2: the following message received over an insecure connection
connection
OPTIONS * HTTP/1.1 OPTIONS * HTTP/1.1
Host: www.example.org Host: www.example.org:8080
has an effective request URI of has a target URI of
https://www.example.org http://www.example.org:8080
Recipients of an HTTP/1.0 request that lacks a Host header field If the target URI's authority component is empty and its URI scheme
might need to use heuristics (e.g., examination of the URI path for requires a non-empty authority (as is the case for "http" and
something unique to a particular host) in order to guess the "https"), the server can reject the request or determine whether a
effective request URI's authority component. configured default applies that is consistent with the incoming
connection's context. Context might include connection details like
address and port, what security has been applied, and locally-defined
information specific to that server's configuration. An empty
authority is replaced with the configured default before further
processing of the request.
[new] Supplying a default name for authority within the context of a
secured connection is inherently unsafe if there is any chance that
the user agent's intended authority might differ from the default. A
server that can uniquely identify an authority from the request
context MAY use that identity as a default without this risk.
Alternatively, it might be better to redirect the request to a safe
resource that explains how to obtain a new client.
[new] Note that reconstructing the client's target URI is only half of the
process for identifying a target resource. The other half is
determining whether that target URI identifies a resource for which
the server is willing and able to send a response, as defined in
Section 7.4 of [HTTP].
4. Status Line 4. Status Line
The first line of a response message is the status-line, consisting The first line of a response message is the status-line, consisting
of the protocol version, a space (SP), the status code, another of the protocol version, a space (SP), the status code, another
space, a possibly empty textual phrase describing the status code, space, and ending with an OPTIONAL textual phrase describing the
and ending with CRLF. status code.
status-line = HTTP-version SP status-code SP reason-phrase CRLF status-line = HTTP-version SP status-code SP [reason-phrase]
Although the request-line and status-line grammar rules require that Although the status-line grammar rule requires that each of the
each of the component elements be separated by a single SP octet, component elements be separated by a single SP octet, recipients MAY
recipients MAY instead parse on whitespace-delimited word boundaries instead parse on whitespace-delimited word boundaries and, aside from
and, aside from the CRLF terminator, treat any form of whitespace as the line terminator, treat any form of whitespace as the SP separator
the SP separator while ignoring preceding or trailing whitespace; while ignoring preceding or trailing whitespace; such whitespace
such whitespace includes one or more of the following octets: SP, includes one or more of the following octets: SP, HTAB, VT (%x0B), FF
HTAB, VT (%x0B), FF (%x0C), or bare CR. However, lenient parsing can (%x0C), or bare CR. However, lenient parsing can result in response
result in security vulnerabilities if there are multiple recipients splitting security vulnerabilities if there are multiple recipients
of the message and each has its own unique interpretation of of the message and each has its own unique interpretation of
robustness (see Section 9.5). robustness (see Section 11.1).
The status-code element is a 3-digit integer code describing the The status-code element is a 3-digit integer code describing the
result of the server's attempt to understand and satisfy the client's result of the server's attempt to understand and satisfy the client's
corresponding request. The rest of the response message is to be corresponding request. A recipient parses and interprets the
interpreted in light of the semantics defined for that status code. remainder of the response message in light of the semantics defined
See Section 6 of [RFC7231] for information about the semantics of for that status code, if the status code is recognized by that
status codes, including the classes of status code (indicated by the recipient, or in accordance with the class of that status code when
first digit), the status codes defined by this specification, the specific code is unrecognized.
considerations for the definition of new status codes, and the IANA
registry.
status-code = 3DIGIT status-code = 3DIGIT
HTTP's core status codes are defined in Section 15 of [HTTP], along
with the classes of status codes, considerations for the definition
of new status codes, and the IANA registry for collecting such
definitions.
The reason-phrase element exists for the sole purpose of providing a The reason-phrase element exists for the sole purpose of providing a
textual description associated with the numeric status code, mostly textual description associated with the numeric status code, mostly
out of deference to earlier Internet application protocols that were out of deference to earlier Internet application protocols that were
more frequently used with interactive text clients. A client SHOULD more frequently used with interactive text clients.
ignore the reason-phrase content.
reason-phrase = *( HTAB / SP / VCHAR / obs-text ) reason-phrase = 1*( HTAB / SP / VCHAR / obs-text )
A client SHOULD ignore the reason-phrase content because it is not a
reliable channel for information (it might be translated for a given
locale, overwritten by intermediaries, or discarded when the message
is forwarded via other versions of HTTP). A server MUST send the
space that separates status-code from the reason-phrase even when the
reason-phrase is absent (i.e., the status-line would end with the
three octets SP CR LF).
5. Field Syntax 5. Field Syntax
Each header field consists of a case-insensitive field name followed Each field line consists of a case-insensitive field name followed by
by a colon (":"), optional leading whitespace, the field value, and a colon (":"), optional leading whitespace, the field line value, and
optional trailing whitespace. optional trailing whitespace.
header-field = field-name ":" OWS field-value OWS field-line = field-name ":" OWS field-value OWS
[new] Most HTTP field names and the rules for parsing within field values
are defined in Section 6.3 of [HTTP]. This section covers the
generic syntax for header field inclusion within, and extraction
from, HTTP/1.1 messages.
5.1. Field Parsing 5.1. Field Line Parsing
Messages are parsed using a generic algorithm, independent of the Messages are parsed using a generic algorithm, independent of the
individual header field names. The contents within a given field individual field names. The contents within a given field line value
value are not parsed until a later stage of message interpretation are not parsed until a later stage of message interpretation (usually
(usually after the message's entire header section has been after the message's entire field section has been processed).
processed).
No whitespace is allowed between the header field-name and colon. In No whitespace is allowed between the field name and colon. In the
the past, differences in the handling of such whitespace have led to past, differences in the handling of such whitespace have led to
security vulnerabilities in request routing and response handling. A security vulnerabilities in request routing and response handling. A
server MUST reject any received request message that contains server MUST reject, with a response status code of 400 (Bad Request),
whitespace between a header field-name and colon with a response code any received request message that contains whitespace between a
of 400 (Bad Request). A proxy MUST remove any such whitespace from a header field name and colon. A proxy MUST remove any such whitespace
response message before forwarding the message downstream. from a response message before forwarding the message downstream.
A field value might be preceded and/or followed by optional A field line value might be preceded and/or followed by optional
whitespace (OWS); a single SP preceding the field-value is preferred whitespace (OWS); a single SP preceding the field line value is
for consistent readability by humans. The field value does not preferred for consistent readability by humans. The field line value
include any leading or trailing whitespace: OWS occurring before the does not include that leading or trailing whitespace: OWS occurring
first non-whitespace octet of the field value or after the last before the first non-whitespace octet of the field line value, or
non-whitespace octet of the field value ought to be excluded by after the last non-whitespace octet of the field line value, is
parsers when extracting the field value from a header field. excluded by parsers when extracting the field line value from a field
line.
5.2. Obsolete Line Folding 5.2. Obsolete Line Folding
Historically, HTTP header field values could be extended over Historically, HTTP/1.x field values could be extended over multiple
multiple lines by preceding each extra line with at least one space lines by preceding each extra line with at least one space or
or horizontal tab (obs-fold). This specification deprecates such horizontal tab (obs-fold). This specification deprecates such line
line folding except within the message/http media type folding except within the message/http media type (Section 10.1).
(Section 8.3.1).
obs-fold = CRLF 1*( SP / HTAB ) obs-fold = OWS CRLF RWS
; obsolete line folding ; obsolete line folding
; see Section 3.2.4
A sender MUST NOT generate a message that includes A sender MUST NOT generate a message that includes line folding
line folding (i.e., that has any field-value that contains a match to (i.e., that has any field line value that contains a match to the
the obs-fold rule) unless the message is intended for packaging obs-fold rule) unless the message is intended for packaging within
within the message/http media type. the message/http media type.
A server that receives an obs-fold in a request message that is not A server that receives an obs-fold in a request message that is not
within a message/http container MUST either reject the message by within a message/http container MUST either reject the message by
sending a 400 (Bad Request), preferably with a representation sending a 400 (Bad Request), preferably with a representation
explaining that obsolete line folding is unacceptable, or replace explaining that obsolete line folding is unacceptable, or replace
each received obs-fold with one or more SP octets prior to each received obs-fold with one or more SP octets prior to
interpreting the field value or forwarding the message downstream. interpreting the field value or forwarding the message downstream.
A proxy or gateway that receives an obs-fold in a response message A proxy or gateway that receives an obs-fold in a response message
that is not within a message/http container MUST either discard the that is not within a message/http container MUST either discard the
skipping to change at line 766 skipping to change at page 17, line 45
octets prior to interpreting the field value or forwarding the octets prior to interpreting the field value or forwarding the
message downstream. message downstream.
A user agent that receives an obs-fold in a response message that is A user agent that receives an obs-fold in a response message that is
not within a message/http container MUST replace each received not within a message/http container MUST replace each received
obs-fold with one or more SP octets prior to interpreting the field obs-fold with one or more SP octets prior to interpreting the field
value. value.
6. Message Body 6. Message Body
The message body (if any) of an HTTP message is used to carry the The message body (if any) of an HTTP/1.1 message is used to carry
payload body of that request or response. The message body is content (Section 6.4 of [HTTP]) for the request or response. The
identical to the payload body unless a transfer coding has been message body is identical to the content unless a transfer coding has
applied, as described in Section 3.3.1. been applied, as described in Section 6.1.
message-body = *OCTET message-body = *OCTET
The rules for when a message body is allowed in a message differ for The rules for determining when a message body is present in an
requests and responses. HTTP/1.1 message differ for requests and responses.
The presence of a message body in a request is signaled by a The presence of a message body in a request is signaled by a
Content-Length or Transfer-Encoding header field. Request message Content-Length or Transfer-Encoding header field. Request message
framing is independent of method semantics, even if the method does framing is independent of method semantics.
not define any use for a message body.
The presence of a message body in a response depends on both the The presence of a message body in a response depends on both the
request method to which it is responding and the response status code request method to which it is responding and the response status code
(Section 3.1.2). (Section 4), and corresponds to when content is allowed; see
Section 6.4 of [HTTP].
6.1. Transfer-Encoding 6.1. Transfer-Encoding
The Transfer-Encoding header field lists the transfer coding names The Transfer-Encoding header field lists the transfer coding names
corresponding to the sequence of transfer codings that have been (or corresponding to the sequence of transfer codings that have been (or
will be) applied to the payload body in order to form the message will be) applied to the content in order to form the message body.
body. Transfer codings are defined in Section 4. Transfer codings are defined in Section 7.
Transfer-Encoding = 1#transfer-coding Transfer-Encoding = #transfer-coding
; defined in [HTTP], Section 10.1.4
Transfer-Encoding is analogous to the Content-Transfer-Encoding field Transfer-Encoding is analogous to the Content-Transfer-Encoding field
of MIME, which was designed to enable safe transport of binary data of MIME, which was designed to enable safe transport of binary data
over a 7-bit transport service ([RFC2045], Section 6). However, safe over a 7-bit transport service ([RFC2045], Section 6). However, safe
transport has a different focus for an 8bit-clean transfer protocol. transport has a different focus for an 8bit-clean transfer protocol.
In HTTP's case, Transfer-Encoding is primarily intended to accurately In HTTP's case, Transfer-Encoding is primarily intended to accurately
delimit a dynamically generated payload and to distinguish payload delimit dynamically generated content. It also serves to distinguish
encodings that are only applied for transport efficiency or security encodings that are only applied in transit from the encodings that
from those that are characteristics of the selected resource. are a characteristic of the selected representation.
A recipient MUST be able to parse the chunked transfer coding A recipient MUST be able to parse the chunked transfer coding
(Section 4.1) because it plays a crucial role in framing messages (Section 7.1) because it plays a crucial role in framing messages
when the payload body size is not known in advance. A sender MUST when the content size is not known in advance. A sender MUST NOT
NOT apply chunked more than once to a message body (i.e., chunking an apply the chunked transfer coding more than once to a message body
already chunked message is not allowed). If any transfer coding (i.e., chunking an already chunked message is not allowed). If any
other than chunked is applied to a request payload body, the sender transfer coding other than chunked is applied to a request's content,
MUST apply chunked as the final transfer coding to ensure that the the sender MUST apply chunked as the final transfer coding to ensure
message is properly framed. If any transfer coding other than that the message is properly framed. If any transfer coding other
chunked is applied to a response payload body, the sender MUST either than chunked is applied to a response's content, the sender MUST
apply chunked as the final transfer coding or terminate the message either apply chunked as the final transfer coding or terminate the
by closing the connection. message by closing the connection.
For example, For example,
Transfer-Encoding: gzip, chunked Transfer-Encoding: gzip, chunked
indicates that the content has been compressed using the gzip coding
indicates that the payload body has been compressed using the gzip and then chunked using the chunked coding while forming the message
coding and then chunked using the chunked coding while forming the body.
message body.
Unlike Content-Encoding (Section 3.1.2.1 of [RFC7231]), Unlike Content-Encoding (Section 8.4.1 of [HTTP]), Transfer-Encoding
Transfer-Encoding is a property of the message, not of the is a property of the message, not of the representation, and any
representation, and any recipient along the request/response chain recipient along the request/response chain MAY decode the received
MAY decode the received transfer coding(s) or apply additional transfer coding(s) or apply additional transfer coding(s) to the
transfer coding(s) to the message body, assuming that corresponding message body, assuming that corresponding changes are made to the
changes are made to the Transfer-Encoding field-value. Additional Transfer-Encoding field value. Additional information about the
information about the encoding parameters can be provided by other encoding parameters can be provided by other header fields not
header fields not defined by this specification. defined by this specification.
Transfer-Encoding MAY be sent in a response to a HEAD request or in a Transfer-Encoding MAY be sent in a response to a HEAD request or in a
304 (Not Modified) response (Section 4.1 of [RFC7232]) to a GET 304 (Not Modified) response (Section 15.4.5 of [HTTP]) to a GET
request, neither of which includes a message body, to indicate that request, neither of which includes a message body, to indicate that
the origin server would have applied a transfer coding to the message the origin server would have applied a transfer coding to the message
body if the request had been an unconditional GET. This indication body if the request had been an unconditional GET. This indication
is not required, however, because any recipient on the response chain is not required, however, because any recipient on the response chain
(including the origin server) can remove transfer codings when they (including the origin server) can remove transfer codings when they
are not needed. are not needed.
A server MUST NOT send a Transfer-Encoding header field in any A server MUST NOT send a Transfer-Encoding header field in any
response with a status code of 1xx (Informational) or 204 (No response with a status code of 1xx (Informational) or 204 (No
Content). A server MUST NOT send a Transfer-Encoding header field in Content). A server MUST NOT send a Transfer-Encoding header field in
any 2xx (Successful) response to a CONNECT request (Section 4.3.6 of any 2xx (Successful) response to a CONNECT request (Section 9.3.6 of
[RFC7231]). [HTTP]).
A server that receives a request message with a transfer coding it
does not understand SHOULD respond with 501 (Not Implemented).
Transfer-Encoding was added in HTTP/1.1. It is generally assumed Transfer-Encoding was added in HTTP/1.1. It is generally assumed
that implementations advertising only HTTP/1.0 support will not that implementations advertising only HTTP/1.0 support will not
understand how to process a transfer-encoded payload. A client MUST understand how to process transfer-encoded content, and that an
NOT send a request containing Transfer-Encoding unless it knows the HTTP/1.0 message received with a Transfer-Encoding is likely to have
server will handle HTTP/1.1 (or later) requests; such knowledge might been forwarded without proper handling of the chunked encoding in
be in the form of specific user configuration or by remembering the transit.
version of a prior received response. A server MUST NOT send a
response containing Transfer-Encoding unless the corresponding
request indicates HTTP/1.1 (or later).
A server that receives a request message with a transfer coding it A client MUST NOT send a request containing Transfer-Encoding unless
does not understand SHOULD respond with 501 (Not Implemented). it knows the server will handle HTTP/1.1 requests (or later minor
revisions); such knowledge might be in the form of specific user
configuration or by remembering the version of a prior received
response. A server MUST NOT send a response containing Transfer-
Encoding unless the corresponding request indicates HTTP/1.1 (or
later minor revisions).
Early implementations of Transfer-Encoding would occasionally send
both a chunked encoding for message framing and an estimated Content-
Length header field for use by progress bars. This is why Transfer-
Encoding is defined as overriding Content-Length, as opposed to them
being mutually incompatible. Unfortunately, forwarding such a
message can lead to vulnerabilities regarding request smuggling
(Section 11.2) or response splitting (Section 11.1) attacks if any
downstream recipient fails to parse the message according to this
specification, particularly when a downstream recipient only
implements HTTP/1.0.
A server MAY reject a request that contains both Content-Length and
Transfer-Encoding or process such a request in accordance with the
Transfer-Encoding alone. Regardless, the server MUST close the
connection after responding to such a request to avoid the potential
attacks.
A server or client that receives an HTTP/1.0 message containing a
Transfer-Encoding header field MUST treat the message as if the
framing is faulty, even if a Content-Length is present, and close the
connection after processing the message. The message sender might
have retained a portion of the message, in buffer, that could be
misinterpreted by further use of the connection.
6.2. Content-Length 6.2. Content-Length
When a message does not have a Transfer-Encoding header field, a When a message does not have a Transfer-Encoding header field, a
Content-Length header field can provide the anticipated size, as a Content-Length header field (Section 8.6 of [HTTP]) can provide the
decimal number of octets, for a potential payload body. For messages anticipated size, as a decimal number of octets, for potential
that do include a payload body, the Content-Length field-value content. For messages that do include content, the Content-Length
provides the framing information necessary for determining where the field value provides the framing information necessary for
body (and message) ends. For messages that do not include a payload determining where the data (and message) ends. For messages that do
body, the Content-Length indicates the size of the selected not include content, the Content-Length indicates the size of the
representation (Section 3 of [RFC7231]). selected representation (Section 8.6 of [HTTP]).
Note: HTTP's use of Content-Length for message framing differs A sender MUST NOT send a Content-Length header field in any message
significantly from the same field's use in MIME, where it is an that contains a Transfer-Encoding header field.
optional field used only within the "message/external-body"
media-type. | *Note:* HTTP's use of Content-Length for message framing
| differs significantly from the same field's use in MIME, where
| it is an optional field used only within the "message/external-
| body" media-type.
6.3. Message Body Length 6.3. Message Body Length
The length of a message body is determined by one of the following The length of a message body is determined by one of the following
(in order of precedence): (in order of precedence):
1. Any response to a HEAD request and any response with a 1xx 1. Any response to a HEAD request and any response with a 1xx
(Informational), 204 (No Content), or 304 (Not Modified) status (Informational), 204 (No Content), or 304 (Not Modified) status
code is always terminated by the first empty line after the code is always terminated by the first empty line after the
header fields, regardless of the header fields present in the header fields, regardless of the header fields present in the
message, and thus cannot contain a message body. message, and thus cannot contain a message body or trailer
section.
2. Any 2xx (Successful) response to a CONNECT request implies that 2. Any 2xx (Successful) response to a CONNECT request implies that
the connection will become a tunnel immediately after the empty the connection will become a tunnel immediately after the empty
line that concludes the header fields. A client MUST ignore any line that concludes the header fields. A client MUST ignore any
Content-Length or Transfer-Encoding header fields received in Content-Length or Transfer-Encoding header fields received in
such a message. such a message.
3. If a message is received with both a Transfer-Encoding and a 3. If a message is received with both a Transfer-Encoding and a
Content-Length header field, the Transfer-Encoding overrides the Content-Length header field, the Transfer-Encoding overrides the
Content-Length. Such a message might indicate an attempt to Content-Length. Such a message might indicate an attempt to
perform request smuggling (Section 9.5) or response splitting perform request smuggling (Section 11.2) or response splitting
(Section 9.4) and ought to be handled as an error. A sender MUST (Section 11.1) and ought to be handled as an error. An
remove the received Content-Length field prior to forwarding such intermediary that chooses to forward the message MUST first
a message downstream. remove the received Content-Length field and process the
Transfer-Encoding (as described below) prior to forwarding the
message downstream.
4. If a Transfer-Encoding header field is present and the chunked 4. If a Transfer-Encoding header field is present and the chunked
transfer coding (Section 4.1) is the final encoding, the message transfer coding (Section 7.1) is the final encoding, the message
body length is determined by reading and decoding the chunked body length is determined by reading and decoding the chunked
data until the transfer coding indicates the data is complete. data until the transfer coding indicates the data is complete.
If a Transfer-Encoding header field is present in a response and If a Transfer-Encoding header field is present in a response and
the chunked transfer coding is not the final encoding, the the chunked transfer coding is not the final encoding, the
message body length is determined by reading the connection until message body length is determined by reading the connection until
it is closed by the server. it is closed by the server.
If a Transfer-Encoding header field is present in a request and If a Transfer-Encoding header field is present in a request and
the chunked transfer coding is not the final encoding, the the chunked transfer coding is not the final encoding, the
message body length cannot be determined reliably; the server message body length cannot be determined reliably; the server
MUST respond with the 400 (Bad Request) status code and then MUST respond with the 400 (Bad Request) status code and then
close the connection. close the connection.
5. If a message is received without Transfer-Encoding and with 5. If a message is received without Transfer-Encoding and with an
either multiple Content-Length header fields having differing invalid Content-Length header field, then the message framing is
field-values or a single Content-Length header field having an invalid and the recipient MUST treat it as an unrecoverable
invalid value, then the message framing is invalid and the error, unless the field value can be successfully parsed as a
recipient MUST treat it as an unrecoverable error. If this is a comma-separated list (Section 5.6.1 of [HTTP]), all values in the
list are valid, and all values in the list are the same (in which
case the message is processed with that single value used as the
Content-Length field value). If the unrecoverable error is in a
request message, the server MUST respond with a 400 (Bad Request) request message, the server MUST respond with a 400 (Bad Request)
status code and then close the connection. If this is a response status code and then close the connection. If it is in a
message received by a proxy, the proxy MUST close the connection response message received by a proxy, the proxy MUST close the
to the server, discard the received response, and send a 502 (Bad connection to the server, discard the received response, and send
Gateway) response to the client. If this is a response message a 502 (Bad Gateway) response to the client. If it is in a
received by a user agent, the user agent MUST close the response message received by a user agent, the user agent MUST
connection to the server and discard the received response. close the connection to the server and discard the received
response.
6. If a valid Content-Length header field is present without 6. If a valid Content-Length header field is present without
Transfer-Encoding, its decimal value defines the expected message Transfer-Encoding, its decimal value defines the expected message
body length in octets. If the sender closes the connection or body length in octets. If the sender closes the connection or
the recipient times out before the indicated number of octets are the recipient times out before the indicated number of octets are
received, the recipient MUST consider the message to be received, the recipient MUST consider the message to be
incomplete and close the connection. incomplete and close the connection.
7. If this is a request message and none of the above are true, then 7. If this is a request message and none of the above are true, then
the message body length is zero (no message body is present). the message body length is zero (no message body is present).
8. Otherwise, this is a response message without a declared message 8. Otherwise, this is a response message without a declared message
body length, so the message body length is determined by the body length, so the message body length is determined by the
number of octets received prior to the server closing the number of octets received prior to the server closing the
connection. connection.
Since there is no way to distinguish a successfully completed, Since there is no way to distinguish a successfully completed, close-
close-delimited message from a partially received message interrupted delimited response message from a partially received message
by network failure, a server SHOULD generate encoding or interrupted by network failure, a server SHOULD generate encoding or
length-delimited messages whenever possible. The close-delimiting length-delimited messages whenever possible. The close-delimiting
feature exists primarily for backwards compatibility with HTTP/1.0. feature exists primarily for backwards compatibility with HTTP/1.0.
| *Note:* Request messages are never close-delimited because they
| are always explicitly framed by length or transfer coding, with
| the absence of both implying the request ends immediately after
| the header section.
A server MAY reject a request that contains a message body but not a A server MAY reject a request that contains a message body but not a
Content-Length by responding with 411 (Length Required). Content-Length by responding with 411 (Length Required).
Unless a transfer coding other than chunked has been applied, a Unless a transfer coding other than chunked has been applied, a
client that sends a request containing a message body SHOULD use a client that sends a request containing a message body SHOULD use a
valid Content-Length header field if the message body length is known valid Content-Length header field if the message body length is known
in advance, rather than the chunked transfer coding, since some in advance, rather than the chunked transfer coding, since some
existing services respond to chunked with a 411 (Length Required) existing services respond to chunked with a 411 (Length Required)
status code even though they understand the chunked transfer coding. status code even though they understand the chunked transfer coding.
This is typically because such services are implemented via a gateway This is typically because such services are implemented via a gateway
that requires a content-length in advance of being called and the that requires a content-length in advance of being called and the
server is unable or unwilling to buffer the entire request before server is unable or unwilling to buffer the entire request before
processing. processing.
A user agent that sends a request containing a message body MUST send A user agent that sends a request that contains a message body MUST
a valid Content-Length header field if it does not know the server send either a valid Content-Length header field or use the chunked
will handle HTTP/1.1 (or later) requests; such knowledge can be in transfer coding. A client MUST NOT use the chunked transfer encoding
the form of specific user configuration or by remembering the version unless it knows the server will handle HTTP/1.1 (or later) requests;
of a prior received response. such knowledge can be in the form of specific user configuration or
by remembering the version of a prior received response.
If the final response to the last request on a connection has been If the final response to the last request on a connection has been
completely received and there remains additional data to read, a user completely received and there remains additional data to read, a user
agent MAY discard the remaining data or attempt to determine if that agent MAY discard the remaining data or attempt to determine if that
data belongs as part of the prior response body, which might be the data belongs as part of the prior message body, which might be the
case if the prior message's Content-Length value is incorrect. A case if the prior message's Content-Length value is incorrect. A
client MUST NOT process, cache, or forward such extra data as a client MUST NOT process, cache, or forward such extra data as a
separate response, since such behavior would be vulnerable to cache separate response, since such behavior would be vulnerable to cache
poisoning. poisoning.
7. Transfer Codings 7. Transfer Codings
Transfer coding names are used to indicate an encoding transformation Transfer coding names are used to indicate an encoding transformation
that has been, can be, or might need to be applied to a payload body that has been, can be, or might need to be applied to a message's
in order to ensure "safe transport" through the network. This content in order to ensure "safe transport" through the network.
differs from a content coding in that the transfer coding is a This differs from a content coding in that the transfer coding is a
property of the message rather than a property of the representation property of the message rather than a property of the representation
that is being transferred. that is being transferred.
transfer-coding = "chunked" ; Section 4.1
/ "compress" ; Section 4.2.1
/ "deflate" ; Section 4.2.2
/ "gzip" ; Section 4.2.3
/ transfer-extension
transfer-extension = token *( OWS ";" OWS transfer-parameter )
Parameters are in the form of a name or name=value pair.
transfer-parameter = token BWS "=" BWS ( token / quoted-string )
All transfer-coding names are case-insensitive and ought to be All transfer-coding names are case-insensitive and ought to be
registered within the HTTP Transfer Coding registry, as defined in registered within the HTTP Transfer Coding registry, as defined in
Section 8.4. They are used in the TE (Section 4.3) and Section 7.3. They are used in the Transfer-Encoding (Section 6.1)
Transfer-Encoding (Section 3.3.1) header fields. and TE (Section 10.1.4 of [HTTP]) header fields (the latter also
defining the "transfer-coding" grammar).
7.1. Chunked Transfer Coding 7.1. Chunked Transfer Coding
The chunked transfer coding wraps the payload body in order to The chunked transfer coding wraps content in order to transfer it as
transfer it as a series of chunks, each with its own size indicator, a series of chunks, each with its own size indicator, followed by an
followed by an OPTIONAL trailer containing header fields. Chunked OPTIONAL trailer section containing trailer fields. Chunked enables
enables content streams of unknown size to be transferred as a content streams of unknown size to be transferred as a sequence of
sequence of length-delimited buffers, which enables the sender to length-delimited buffers, which enables the sender to retain
retain connection persistence and the recipient to know when it has connection persistence and the recipient to know when it has received
received the entire message. the entire message.
chunked-body = *chunk chunked-body = *chunk
last-chunk last-chunk
trailer-part trailer-section
CRLF CRLF
chunk = chunk-size [ chunk-ext ] CRLF chunk = chunk-size [ chunk-ext ] CRLF
chunk-data CRLF chunk-data CRLF
chunk-size = 1*HEXDIG chunk-size = 1*HEXDIG
last-chunk = 1*("0") [ chunk-ext ] CRLF last-chunk = 1*("0") [ chunk-ext ] CRLF
chunk-data = 1*OCTET ; a sequence of chunk-size octets chunk-data = 1*OCTET ; a sequence of chunk-size octets
The chunk-size field is a string of hex digits indicating the size of The chunk-size field is a string of hex digits indicating the size of
the chunk-data in octets. The chunked transfer coding is complete the chunk-data in octets. The chunked transfer coding is complete
when a chunk with a chunk-size of zero is received, possibly followed when a chunk with a chunk-size of zero is received, possibly followed
by a trailer, and finally terminated by an empty line. by a trailer section, and finally terminated by an empty line.
A recipient MUST be able to parse and decode the chunked transfer A recipient MUST be able to parse and decode the chunked transfer
coding. coding.
HTTP/1.1 does not define any means to limit the size of a chunked
response such that an intermediary can be assured of buffering the
entire response. Additionally, very large chunk sizes may cause
overflows or loss of precision if their values are not represented
accurately in a receiving implementation. Therefore, recipients MUST
anticipate potentially large hexadecimal numerals and prevent parsing
errors due to integer conversion overflows or precision loss due to
integer representation.
The chunked encoding does not define any parameters. Their presence
SHOULD be treated as an error.
7.1.1. Chunk Extensions 7.1.1. Chunk Extensions
The chunked encoding allows each chunk to include zero or more chunk The chunked encoding allows each chunk to include zero or more chunk
extensions, immediately following the chunk-size, for the sake of extensions, immediately following the chunk-size, for the sake of
supplying per-chunk metadata (such as a signature or hash), supplying per-chunk metadata (such as a signature or hash), mid-
mid-message control information, or randomization of message body message control information, or randomization of message body size.
size.
chunk-ext = *( ";" chunk-ext-name [ "=" chunk-ext-val ] ) chunk-ext = *( BWS ";" BWS chunk-ext-name
[ BWS "=" BWS chunk-ext-val ] )
chunk-ext-name = token chunk-ext-name = token
chunk-ext-val = token / quoted-string chunk-ext-val = token / quoted-string
The chunked encoding is specific to each connection and is likely to The chunked encoding is specific to each connection and is likely to
be removed or recoded by each recipient (including intermediaries) be removed or recoded by each recipient (including intermediaries)
before any higher-level application would have a chance to inspect before any higher-level application would have a chance to inspect
the extensions. Hence, use of chunk extensions is generally limited the extensions. Hence, use of chunk extensions is generally limited
to specialized HTTP services such as "long polling" (where client and to specialized HTTP services such as "long polling" (where client and
server can have shared expectations regarding the use of chunk server can have shared expectations regarding the use of chunk
extensions) or for padding within an end-to-end secured connection. extensions) or for padding within an end-to-end secured connection.
A recipient MUST ignore unrecognized chunk extensions. A server A recipient MUST ignore unrecognized chunk extensions. A server
ought to limit the total length of chunk extensions received in a ought to limit the total length of chunk extensions received in a
request to an amount reasonable for the services provided, in the request to an amount reasonable for the services provided, in the
same way that it applies length limitations and timeouts for other same way that it applies length limitations and timeouts for other
parts of a message, and generate an appropriate 4xx (Client Error) parts of a message, and generate an appropriate 4xx (Client Error)
response if that amount is exceeded. response if that amount is exceeded.
7.1.2. Chunked Trailer Part 7.1.2. Chunked Trailer Section
A trailer allows the sender to include additional fields at the end A trailer section allows the sender to include additional fields at
of a chunked message in order to supply metadata that might be the end of a chunked message in order to supply metadata that might
dynamically generated while the message body is sent, such as a be dynamically generated while the content is sent, such as a message
message integrity check, digital signature, or post-processing integrity check, digital signature, or post-processing status. The
status. The trailer fields are identical to header fields, except proper use and limitations of trailer fields are defined in
they are sent in a chunked trailer instead of the message's header Section 6.5 of [HTTP].
section.
trailer-part = *( header-field CRLF ) trailer-section = *( field-line CRLF )
When a chunked message containing a non-empty trailer is received, A recipient that removes the chunked encoding from a message MAY
the recipient MAY process the fields (aside from those forbidden selectively retain or discard the received trailer fields. A
above) as if they were appended to the message's header section. A recipient that retains a received trailer field MUST either store/
recipient MUST ignore (or consider as an error) any fields that are forward the trailer field separately from the received header fields
forbidden to be sent in a trailer, since processing them as if they or merge the received trailer field into the header section. A
were present in the header section might bypass external security recipient MUST NOT merge a received trailer field into the header
filters. section unless its corresponding header field definition explicitly
permits and instructs how the trailer field value can be safely
merged.
7.1.3. Decoding Chunked 7.1.3. Decoding Chunked
A process for decoding the chunked transfer coding can be represented A process for decoding the chunked transfer coding can be represented
in pseudo-code as: in pseudo-code as:
length := 0 length := 0
read chunk-size, chunk-ext (if any), and CRLF read chunk-size, chunk-ext (if any), and CRLF
while (chunk-size > 0) { while (chunk-size > 0) {
read chunk-data and CRLF read chunk-data and CRLF
append chunk-data to decoded-body append chunk-data to content
length := length + chunk-size length := length + chunk-size
read chunk-size, chunk-ext (if any), and CRLF read chunk-size, chunk-ext (if any), and CRLF
} }
read trailer field read trailer field
while (trailer field is not empty) { while (trailer field is not empty) {
if (trailer field is allowed to be sent in a trailer) { if (trailer fields are stored/forwarded separately) {
append trailer field to existing header fields append trailer field to existing trailer fields
} }
read trailer-field else if (trailer field is understood and defined as mergeable) {
merge trailer field with existing header fields
}
else {
discard trailer field
}
read trailer field
} }
Content-Length := length Content-Length := length
Remove "chunked" from Transfer-Encoding Remove "chunked" from Transfer-Encoding
Remove Trailer from existing header fields
7.2. Compression Codings 7.2. Transfer Codings for Compression
The codings defined below can be used to compress the payload of a The following transfer coding names for compression are defined by
message. the same algorithm as their corresponding content coding:
compress (and x-compress)
See Section 8.4.1.1 of [HTTP].
deflate
See Section 8.4.1.2 of [HTTP].
gzip (and x-gzip)
See Section 8.4.1.3 of [HTTP].
The compression codings do not define any parameters. The presence
of parameters with any of these compression codings SHOULD be treated
as an error.
7.3. Transfer Coding Registry 7.3. Transfer Coding Registry
The "HTTP Transfer Coding Registry" defines the namespace for The "HTTP Transfer Coding Registry" defines the namespace for
transfer coding names. It is maintained at transfer coding names. It is maintained at
<http://www.iana.org/assignments/http-parameters>. <https://www.iana.org/assignments/http-parameters>.
8.4.1. Procedure
Registrations MUST include the following fields: Registrations MUST include the following fields:
o Name * Name
o Description * Description
o Pointer to specification text * Pointer to specification text
Names of transfer codings MUST NOT overlap with names of content Names of transfer codings MUST NOT overlap with names of content
codings (Section 3.1.2.1 of [RFC7231]) unless the encoding codings (Section 8.4.1 of [HTTP]) unless the encoding transformation
transformation is identical, as is the case for the compression is identical, as is the case for the compression codings defined in
codings defined in Section 4.2. Section 7.2.
Values to be added to this namespace require IETF Review (see Section The TE header field (Section 10.1.4 of [HTTP]) uses a pseudo
4.1 of [RFC5226]), and MUST conform to the purpose of transfer coding parameter named "q" as rank value when multiple transfer codings are
defined in this specification. acceptable. Future registrations of transfer codings SHOULD NOT
define parameters called "q" (case-insensitively) in order to avoid
ambiguities.
Values to be added to this namespace require IETF Review (see
Section 4.8 of [RFC8126]), and MUST conform to the purpose of
transfer coding defined in this specification.
Use of program names for the identification of encoding formats is Use of program names for the identification of encoding formats is
not desirable and is discouraged for future encodings. not desirable and is discouraged for future encodings.
7.4. Negotiating Transfer Codings 7.4. Negotiating Transfer Codings
The TE field (Section 10.1.4 of [HTTP]) is used in HTTP/1.1 to
indicate what transfer-codings, besides chunked, the client is
willing to accept in the response, and whether the client is willing
to preserve trailer fields in a chunked transfer coding.
A client MUST NOT send the chunked transfer coding name in TE;
chunked is always acceptable for HTTP/1.1 recipients.
Three examples of TE use are below. Three examples of TE use are below.
TE: deflate TE: deflate
TE: TE:
TE: trailers, deflate;q=0.5 TE: trailers, deflate;q=0.5
When multiple transfer codings are acceptable, the client MAY rank When multiple transfer codings are acceptable, the client MAY rank
the codings by preference using a case-insensitive "q" parameter the codings by preference using a case-insensitive "q" parameter
(similar to the qvalues used in content negotiation fields, Section (similar to the qvalues used in content negotiation fields,
5.3.1 of [RFC7231]). The rank value is a real number in the range 0 Section 12.4.2 of [HTTP]). The rank value is a real number in the
through 1, where 0.001 is the least preferred and 1 is the most range 0 through 1, where 0.001 is the least preferred and 1 is the
preferred; a value of 0 means "not acceptable". most preferred; a value of 0 means "not acceptable".
If the TE field-value is empty or if no TE field is present, the only If the TE field value is empty or if no TE field is present, the only
acceptable transfer coding is chunked. A message with no transfer acceptable transfer coding is chunked. A message with no transfer
coding is always acceptable. coding is always acceptable.
The presence of the keyword "trailers" indicates that the client is The keyword "trailers" indicates that the sender will not discard
willing to accept trailer fields in a chunked transfer coding, as trailer fields, as described in Section 6.5 of [HTTP].
defined in Section 4.1.2, on behalf of itself and any downstream
clients. For requests from an intermediary, this implies that
either: (a) all downstream clients are willing to accept trailer
fields in the forwarded response; or, (b) the intermediary will
attempt to buffer the response on behalf of downstream recipients.
Note that HTTP/1.1 does not define any means to limit the size of a
chunked response such that an intermediary can be assured of
buffering the entire response.
Since the TE header field only applies to the immediate connection, a Since the TE header field only applies to the immediate connection, a
sender of TE MUST also send a "TE" connection option within the sender of TE MUST also send a "TE" connection option within the
Connection header field (Section 6.1) in order to prevent the TE Connection header field (Section 7.6.1 of [HTTP]) in order to prevent
field from being forwarded by intermediaries that do not support its the TE header field from being forwarded by intermediaries that do
semantics. not support its semantics.
8. Handling Incomplete Messages 8. Handling Incomplete Messages
A server that receives an incomplete request message, usually due to A server that receives an incomplete request message, usually due to
a canceled request or a triggered timeout exception, MAY send an a canceled request or a triggered timeout exception, MAY send an
error response prior to closing the connection. error response prior to closing the connection.
A client that receives an incomplete response message, which can A client that receives an incomplete response message, which can
occur when a connection is closed prematurely or when decoding a occur when a connection is closed prematurely or when decoding a
supposedly chunked transfer coding fails, MUST record the message as supposedly chunked transfer coding fails, MUST record the message as
incomplete. Cache requirements for incomplete responses are defined incomplete. Cache requirements for incomplete responses are defined
in Section 3 of [RFC7234]. in Section 3 of [CACHING].
If a response terminates in the middle of the header section (before If a response terminates in the middle of the header section (before
the empty line is received) and the status code might rely on header the empty line is received) and the status code might rely on header
fields to convey the full meaning of the response, then the client fields to convey the full meaning of the response, then the client
cannot assume that meaning has been conveyed; the client might need cannot assume that meaning has been conveyed; the client might need
to repeat the request in order to determine what action to take next. to repeat the request in order to determine what action to take next.
A message body that uses the chunked transfer coding is incomplete if A message body that uses the chunked transfer coding is incomplete if
the zero-sized chunk that terminates the encoding has not been the zero-sized chunk that terminates the encoding has not been
received. A message that uses a valid Content-Length is incomplete received. A message that uses a valid Content-Length is incomplete
if the size of the message body received (in octets) is less than the if the size of the message body received (in octets) is less than the
value given by Content-Length. A response that has neither chunked value given by Content-Length. A response that has neither chunked
transfer coding nor Content-Length is terminated by closure of the transfer coding nor Content-Length is terminated by closure of the
connection and, thus, is considered complete regardless of the number connection and, if the header section was received intact, is
of message body octets received, provided that the header section was considered complete unless an error was indicated by the underlying
received intact. connection (e.g., an "incomplete close" in TLS would leave the
response incomplete, as described in Section 9.8).
9. Connection Management 9. Connection Management
HTTP messaging is independent of the underlying transport- or HTTP messaging is independent of the underlying transport- or
session-layer connection protocol(s). HTTP only presumes a reliable session-layer connection protocol(s). HTTP only presumes a reliable
transport with in-order delivery of requests and the corresponding transport with in-order delivery of requests and the corresponding
in-order delivery of responses. The mapping of HTTP request and in-order delivery of responses. The mapping of HTTP request and
response structures onto the data units of an underlying transport response structures onto the data units of an underlying transport
protocol is outside the scope of this specification. protocol is outside the scope of this specification.
As described in Section 5.2, the specific connection protocols to be As described in Section 7.3 of [HTTP], the specific connection
used for an HTTP interaction are determined by client configuration protocols to be used for an HTTP interaction are determined by client
and the target URI. For example, the "http" URI scheme configuration and the target URI. For example, the "http" URI scheme
(Section 2.7.1) indicates a default connection of TCP over IP, with a (Section 4.2.1 of [HTTP]) indicates a default connection of TCP over
default TCP port of 80, but the client might be configured to use a IP, with a default TCP port of 80, but the client might be configured
proxy via some other connection, port, or protocol. to use a proxy via some other connection, port, or protocol.
HTTP implementations are expected to engage in connection management, HTTP implementations are expected to engage in connection management,
which includes maintaining the state of current connections, which includes maintaining the state of current connections,
establishing a new connection or reusing an existing connection, establishing a new connection or reusing an existing connection,
processing messages received on a connection, detecting connection processing messages received on a connection, detecting connection
failures, and closing each connection. Most clients maintain failures, and closing each connection. Most clients maintain
multiple connections in parallel, including more than one connection multiple connections in parallel, including more than one connection
per server endpoint. Most servers are designed to maintain thousands per server endpoint. Most servers are designed to maintain thousands
of concurrent connections, while controlling request queues to enable of concurrent connections, while controlling request queues to enable
fair use and detect denial-of-service attacks. fair use and detect denial-of-service attacks.
9.2. Establishment 9.1. Establishment
It is beyond the scope of this specification to describe how It is beyond the scope of this specification to describe how
connections are established via various transport- or session-layer connections are established via various transport- or session-layer
protocols. Each connection applies to only one transport link. protocols. Each HTTP connection maps to one underlying transport
connection.
9.3. Associating a Response to a Request 9.2. Associating a Response to a Request
HTTP does not include a request identifier for associating a given HTTP/1.1 does not include a request identifier for associating a
request message with its corresponding one or more response messages. given request message with its corresponding one or more response
Hence, it relies on the order of response arrival to correspond messages. Hence, it relies on the order of response arrival to
exactly to the order in which requests are made on the same correspond exactly to the order in which requests are made on the
connection. More than one response message per request only occurs same connection. More than one response message per request only
when one or more informational responses (1xx, see Section 6.2 of occurs when one or more informational responses (1xx, see
[RFC7231]) precede a final response to the same request. Section 15.2 of [HTTP]) precede a final response to the same request.
A client that has more than one outstanding request on a connection A client that has more than one outstanding request on a connection
MUST maintain a list of outstanding requests in the order sent and MUST maintain a list of outstanding requests in the order sent and
MUST associate each received response message on that connection to MUST associate each received response message on that connection to
the highest ordered request that has not yet received a final the first outstanding request that has not yet received a final (non-
(non-1xx) response. 1xx) response.
If a client receives data on a connection that doesn't have
outstanding requests, the client MUST NOT consider that data to be a
valid response; the client SHOULD close the connection, since message
delimitation is now ambiguous, unless the data consists only of one
or more CRLF (which can be discarded, as per Section 2.2).
9.3. Persistence 9.3. Persistence
HTTP/1.1 defaults to the use of "persistent connections", allowing HTTP/1.1 defaults to the use of _persistent connections_, allowing
multiple requests and responses to be carried over a single multiple requests and responses to be carried over a single
connection. The "close" connection option is used to signal that a connection. HTTP implementations SHOULD support persistent
connection will not persist after the current request/response. HTTP connections.
implementations SHOULD support persistent connections.
A recipient determines whether a connection is persistent or not A recipient determines whether a connection is persistent or not
based on the most recently received message's protocol version and based on the protocol version and Connection header field
Connection header field (if any): (Section 7.6.1 of [HTTP]) in the most recently received message, if
any:
o If the "close" connection option is present, the connection will * If the close connection option is present (Section 9.6), the
not persist after the current response; else, connection will not persist after the current response; else,
o If the received protocol is HTTP/1.1 (or later), the connection * If the received protocol is HTTP/1.1 (or later), the connection
will persist after the current response; else, will persist after the current response; else,
o If the received protocol is HTTP/1.0, the "keep-alive" connection * If the received protocol is HTTP/1.0, the "keep-alive" connection
option is present, the recipient is not a proxy, and the recipient option is present, either the recipient is not a proxy or the
wishes to honor the HTTP/1.0 "keep-alive" mechanism, the message is a response, and the recipient wishes to honor the
connection will persist after the current response; otherwise, HTTP/1.0 "keep-alive" mechanism, the connection will persist after
the current response; otherwise,
o The connection will close after the current response. * The connection will close after the current response.
A client that does not support persistent connections MUST send the A client that does not support persistent connections MUST send the
"close" connection option in every request message. close connection option in every request message.
A server that does not support persistent connections MUST send the A server that does not support persistent connections MUST send the
"close" connection option in every response message that does not close connection option in every response message that does not have
have a 1xx (Informational) status code. a 1xx (Informational) status code.
A client MAY send additional requests on a persistent connection A client MAY send additional requests on a persistent connection
until it sends or receives a "close" connection option or receives an until it sends or receives a close connection option or receives an
HTTP/1.0 response without a "keep-alive" connection option. HTTP/1.0 response without a "keep-alive" connection option.
In order to remain persistent, all messages on a connection need to In order to remain persistent, all messages on a connection need to
have a self-defined message length (i.e., one not defined by closure have a self-defined message length (i.e., one not defined by closure
of the connection), as described in Section 3.3. A server MUST read of the connection), as described in Section 6. A server MUST read
the entire request message body or close the connection after sending the entire request message body or close the connection after sending
its response, since otherwise the remaining data on a persistent its response, since otherwise the remaining data on a persistent
connection would be misinterpreted as the next request. Likewise, a connection would be misinterpreted as the next request. Likewise, a
client MUST read the entire response message body if it intends to client MUST read the entire response message body if it intends to
reuse the same connection for a subsequent request. reuse the same connection for a subsequent request.
A proxy server MUST NOT maintain a persistent connection with an A proxy server MUST NOT maintain a persistent connection with an
HTTP/1.0 client (see Section 19.7.1 of [RFC2068] for information and HTTP/1.0 client (see Section 19.7.1 of [RFC2068] for information and
discussion of the problems with the Keep-Alive header field discussion of the problems with the Keep-Alive header field
implemented by many HTTP/1.0 clients). implemented by many HTTP/1.0 clients).
[new] See Appendix C.2.2 for more information on backwards compatibility
See Appendix A.1.2 for more information on backwards compatibility
with HTTP/1.0 clients. with HTTP/1.0 clients.
9.3.1. Retrying Requests 9.3.1. Retrying Requests
Connections can be closed at any time, with or without intention. Connections can be closed at any time, with or without intention.
Implementations ought to anticipate the need to recover from Implementations ought to anticipate the need to recover from
asynchronous close events. asynchronous close events. The conditions under which a client can
automatically retry a sequence of outstanding requests are defined in
When an inbound connection is closed prematurely, a client MAY open a Section 9.2.2 of [HTTP].
new connection and automatically retransmit an aborted sequence of
requests if all of those requests have idempotent methods (Section
4.2.2 of [RFC7231]).
9.3.2. Pipelining 9.3.2. Pipelining
A client that supports persistent connections MAY "pipeline" its A client that supports persistent connections MAY _pipeline_ its
requests (i.e., send multiple requests without waiting for each requests (i.e., send multiple requests without waiting for each
response). A server MAY process a sequence of pipelined requests in response). A server MAY process a sequence of pipelined requests in
parallel if they all have safe methods (Section 4.2.1 of [RFC7231]), parallel if they all have safe methods (Section 9.2.1 of [HTTP]), but
but it MUST send the corresponding responses in the same order that it MUST send the corresponding responses in the same order that the
the requests were received. requests were received.
A client that pipelines requests SHOULD retry unanswered requests if A client that pipelines requests SHOULD retry unanswered requests if
the connection closes before it receives all of the corresponding the connection closes before it receives all of the corresponding
responses. When retrying pipelined requests after a failed responses. When retrying pipelined requests after a failed
connection (a connection not explicitly closed by the server in its connection (a connection not explicitly closed by the server in its
last complete response), a client MUST NOT pipeline immediately after last complete response), a client MUST NOT pipeline immediately after
connection establishment, since the first remaining request in the connection establishment, since the first remaining request in the
prior pipeline might have caused an error response that can be lost prior pipeline might have caused an error response that can be lost
again if multiple requests are sent on a prematurely closed again if multiple requests are sent on a prematurely closed
connection (see the TCP reset problem described in Section 6.6). connection (see the TCP reset problem described in Section 9.6).
Idempotent methods (Section 4.2.2 of [RFC7231]) are significant to Idempotent methods (Section 9.2.2 of [HTTP]) are significant to
pipelining because they can be automatically retried after a pipelining because they can be automatically retried after a
connection failure. A user agent SHOULD NOT pipeline requests after connection failure. A user agent SHOULD NOT pipeline requests after
a non-idempotent method, until the final response status code for a non-idempotent method, until the final response status code for
that method has been received, unless the user agent has a means to that method has been received, unless the user agent has a means to
detect and recover from partial failure conditions involving the detect and recover from partial failure conditions involving the
pipelined sequence. pipelined sequence.
An intermediary that receives pipelined requests MAY pipeline those An intermediary that receives pipelined requests MAY pipeline those
requests when forwarding them inbound, since it can rely on the requests when forwarding them inbound, since it can rely on the
outbound user agent(s) to determine what requests can be safely outbound user agent(s) to determine what requests can be safely
pipelined. If the inbound connection fails before receiving a pipelined. If the inbound connection fails before receiving a
response, the pipelining intermediary MAY attempt to retry a sequence response, the pipelining intermediary MAY attempt to retry a sequence
of requests that have yet to receive a response if the requests all of requests that have yet to receive a response if the requests all
have idempotent methods; otherwise, the pipelining intermediary have idempotent methods; otherwise, the pipelining intermediary
SHOULD forward any received responses and then close the SHOULD forward any received responses and then close the
corresponding outbound connection(s) so that the outbound user corresponding outbound connection(s) so that the outbound user
agent(s) can recover accordingly. agent(s) can recover accordingly.
6.4. Concurrency 9.4. Concurrency
A client ought to limit the number of simultaneous open connections A client ought to limit the number of simultaneous open connections
that it maintains to a given server. that it maintains to a given server.
Previous revisions of HTTP gave a specific number of connections as a Previous revisions of HTTP gave a specific number of connections as a
ceiling, but this was found to be impractical for many applications. ceiling, but this was found to be impractical for many applications.
As a result, this specification does not mandate a particular maximum As a result, this specification does not mandate a particular maximum
number of connections but, instead, encourages clients to be number of connections but, instead, encourages clients to be
conservative when opening multiple connections. conservative when opening multiple connections.
Multiple connections are typically used to avoid the "head-of-line Multiple connections are typically used to avoid the "head-of-line
blocking" problem, wherein a request that takes significant blocking" problem, wherein a request that takes significant server-
server-side processing and/or has a large payload blocks subsequent side processing and/or transfers very large content would block
requests on the same connection. However, each connection consumes subsequent requests on the same connection. However, each connection
server resources. Furthermore, using multiple connections can cause consumes server resources.
undesirable side effects in congested networks.
Furthermore, using multiple connections can cause undesirable side
effects in congested networks. Using larger numbers of connections
can also cause side effects in otherwise uncongested networks,
because their aggregate and initially synchronized sending behavior
can cause congestion that would not have been present if fewer
parallel connections had been used.
Note that a server might reject traffic that it deems abusive or Note that a server might reject traffic that it deems abusive or
characteristic of a denial-of-service attack, such as an excessive characteristic of a denial-of-service attack, such as an excessive
number of open connections from a single client. number of open connections from a single client.
6.5. Failures and Timeouts 9.5. Failures and Timeouts
Servers will usually have some timeout value beyond which they will Servers will usually have some timeout value beyond which they will
no longer maintain an inactive connection. Proxy servers might make no longer maintain an inactive connection. Proxy servers might make
this a higher value since it is likely that the client will be making this a higher value since it is likely that the client will be making
more connections through the same proxy server. The use of more connections through the same proxy server. The use of
persistent connections places no requirements on the length (or persistent connections places no requirements on the length (or
existence) of this timeout for either the client or the server. existence) of this timeout for either the client or the server.
A client or server that wishes to time out SHOULD issue a graceful A client or server that wishes to time out SHOULD issue a graceful
close on the connection. Implementations SHOULD constantly monitor close on the connection. Implementations SHOULD constantly monitor
skipping to change at line 1404 skipping to change at page 33, line 22
time. For example, a client might have started to send a new request time. For example, a client might have started to send a new request
at the same time that the server has decided to close the "idle" at the same time that the server has decided to close the "idle"
connection. From the server's point of view, the connection is being connection. From the server's point of view, the connection is being
closed while it was idle, but from the client's point of view, a closed while it was idle, but from the client's point of view, a
request is in progress. request is in progress.
A server SHOULD sustain persistent connections, when possible, and A server SHOULD sustain persistent connections, when possible, and
allow the underlying transport's flow-control mechanisms to resolve allow the underlying transport's flow-control mechanisms to resolve
temporary overloads, rather than terminate connections with the temporary overloads, rather than terminate connections with the
expectation that clients will retry. The latter technique can expectation that clients will retry. The latter technique can
exacerbate network congestion. exacerbate network congestion or server load.
A client sending a message body SHOULD monitor the network connection A client sending a message body SHOULD monitor the network connection
for an error response while it is transmitting the request. If the for an error response while it is transmitting the request. If the
client sees a response that indicates the server does not wish to client sees a response that indicates the server does not wish to
receive the message body and is closing the connection, the client receive the message body and is closing the connection, the client
SHOULD immediately cease transmitting the body and close its side of SHOULD immediately cease transmitting the body and close its side of
the connection. the connection.
6.6. Tear-down 9.6. Tear-down
The Connection header field (Section 6.1) provides a "close" The "close" connection option is defined as a signal that the sender
connection option that a sender SHOULD send when it wishes to close will close this connection after completion of the response. A
the connection after the current request/response pair. sender SHOULD send a Connection header field (Section 7.6.1 of
[HTTP]) containing the close connection option when it intends to
close a connection. For example,
A client that sends a "close" connection option MUST NOT send further Connection: close
requests on that connection (after the one containing "close") and
as a request header field indicates that this is the last request
that the client will send on this connection, while in a response the
same field indicates that the server is going to close this
connection after the response message is complete.
Note that the field name "Close" is reserved, since using that name
as a header field might conflict with the close connection option.
A client that sends a close connection option MUST NOT send further
requests on that connection (after the one containing the close) and
MUST close the connection after reading the final response message MUST close the connection after reading the final response message
corresponding to this request. corresponding to this request.
A server that receives a "close" connection option MUST initiate a A server that receives a close connection option MUST initiate
close of the connection (see below) after it sends the final response closure of the connection (see below) after it sends the final
to the request that contained "close". The server SHOULD send a response to the request that contained the close connection option.
"close" connection option in its final response on that connection. The server SHOULD send a close connection option in its final
The server MUST NOT process any further requests received on that response on that connection. The server MUST NOT process any further
connection. requests received on that connection.
A server that sends a "close" connection option MUST initiate a close A server that sends a close connection option MUST initiate closure
of the connection (see below) after it sends the response containing of the connection (see below) after it sends the response containing
"close". The server MUST NOT process any further requests received the close connection option. The server MUST NOT process any further
on that connection. requests received on that connection.
A client that receives a "close" connection option MUST cease sending A client that receives a close connection option MUST cease sending
requests on that connection and close the connection after reading requests on that connection and close the connection after reading
the response message containing the "close"; if additional pipelined the response message containing the close connection option; if
requests had been sent on the connection, the client SHOULD NOT additional pipelined requests had been sent on the connection, the
assume that they will be processed by the server. client SHOULD NOT assume that they will be processed by the server.
If a server performs an immediate close of a TCP connection, there is If a server performs an immediate close of a TCP connection, there is
a significant risk that the client will not be able to read the last a significant risk that the client will not be able to read the last
HTTP response. If the server receives additional data from the HTTP response. If the server receives additional data from the
client on a fully closed connection, such as another request that was client on a fully closed connection, such as another request sent by
sent by the client before receiving the server's response, the the client before receiving the server's response, the server's TCP
server's TCP stack will send a reset packet to the client; stack will send a reset packet to the client; unfortunately, the
unfortunately, the reset packet might erase the client's reset packet might erase the client's unacknowledged input buffers
unacknowledged input buffers before they can be read and interpreted before they can be read and interpreted by the client's HTTP parser.
by the client's HTTP parser.
To avoid the TCP reset problem, servers typically close a connection To avoid the TCP reset problem, servers typically close a connection
in stages. First, the server performs a half-close by closing only in stages. First, the server performs a half-close by closing only
the write side of the read/write connection. The server then the write side of the read/write connection. The server then
continues to read from the connection until it receives a continues to read from the connection until it receives a
corresponding close by the client, or until the server is reasonably corresponding close by the client, or until the server is reasonably
certain that its own TCP stack has received the client's certain that its own TCP stack has received the client's
acknowledgement of the packet(s) containing the server's last acknowledgement of the packet(s) containing the server's last
response. Finally, the server fully closes the connection. response. Finally, the server fully closes the connection.
It is unknown whether the reset problem is exclusive to TCP or might It is unknown whether the reset problem is exclusive to TCP or might
also be found in other transport connection protocols. also be found in other transport connection protocols.
[new] Note that a TCP connection that is half-closed by the client does not
delimit a request message, nor does it imply that the client is no
longer interested in a response. In general, transport signals
cannot be relied upon to signal edge cases, since HTTP/1.1 is
independent of transport.
9.7. TLS Connection Initiation 9.7. TLS Connection Initiation
5.4.3. Initiating HTTP Over TLS [RFC2818] Conceptually, HTTP/TLS is simply sending HTTP messages over a
connection secured via TLS [TLS13].
Conceptually, HTTP/TLS is very simple. Simply use HTTP over TLS
precisely as you would use HTTP over TCP.
The agent acting as the HTTP client should also act as the TLS The HTTP client also acts as the TLS client. It initiates a
client. It should initiate a connection to the server on the connection to the server on the appropriate port and sends the TLS
appropriate port and then send the TLS ClientHello to begin the TLS ClientHello to begin the TLS handshake. When the TLS handshake has
handshake. When the TLS handshake has finished. The client may then finished, the client may then initiate the first HTTP request. All
initiate the first HTTP request. All HTTP data MUST be sent as TLS HTTP data MUST be sent as TLS "application data", but is otherwise
"application data". Normal HTTP behavior, including retained treated like a normal connection for HTTP (including potential reuse
connections should be followed. as a persistent connection).
9.8. TLS Connection Closure 9.8. TLS Connection Closure
TLS provides a facility for secure connection closure. When a valid TLS uses an exchange of closure alerts prior to (non-error)
closure alert is received, an implementation can be assured that no connection closure to provide secure connection closure; see
further data will be received on that connection. TLS Section 6.1 of [TLS13]. When a valid closure alert is received, an
implementations MUST initiate an exchange of closure alerts before implementation can be assured that no further data will be received
closing a connection. A TLS implementation MAY, after sending a on that connection.
closure alert, close the connection without waiting for the peer to
send its closure alert, generating an "incomplete close". Note that
an implementation which does this MAY choose to reuse the session.
This SHOULD only be done when the application knows (typically
through detecting HTTP message boundaries) that it has received all
the message data that it cares about.
As specified in [RFC2246], any implementation which receives a
connection close without first receiving a valid closure alert (a
"premature close") MUST NOT reuse that session. Note that a
premature close does not call into question the security of the data
already received, but simply indicates that subsequent data might
have been truncated. Because TLS is oblivious to HTTP
request/response boundaries, it is necessary to examine the HTTP data
itself (specifically the Content-Length header) to determine whether
the truncation occurred inside a message or between messages.
2.2.1. Client Behavior
Because HTTP uses connection closure to signal end of server data,
client implementations MUST treat any premature closes as errors and
the data received as potentially truncated. While in some cases the
HTTP protocol allows the client to find out whether truncation took
place so that, if it received the complete reply, it may tolerate
such errors following the principle to "[be] strict when sending and
tolerant when receiving" [RFC1958], often truncation does not show in
the HTTP protocol data; two cases in particular deserve special note:
A HTTP response without a Content-Length header. Since data length
in this situation is signalled by connection close a premature
close generated by the server cannot be distinguished from a
spurious close generated by an attacker.
A HTTP response with a valid Content-Length header closed before When an implementation knows that it has sent or received all the
all data has been read. Because TLS does not provide document message data that it cares about, typically by detecting HTTP message
oriented protection, it is impossible to determine whether the boundaries, it might generate an "incomplete close" by sending a
server has miscomputed the Content-Length or an attacker has closure alert and then closing the connection without waiting to
truncated the connection. receive the corresponding closure alert from its peer.
There is one exception to the above rule. An incomplete close does not call into question the security of the
data already received, but it could indicate that subsequent data
might have been truncated. As TLS is not directly aware of HTTP
message framing, it is necessary to examine the HTTP data itself to
determine whether messages were complete. Handling of incomplete
messages is defined in Section 8.
When encountering a premature close, a client SHOULD treat as When encountering an incomplete close, a client SHOULD treat as
completed all requests for which it has received as much data as completed all requests for which it has received as much data as
specified in the Content-Length header. specified in the Content-Length header or, when a Transfer-Encoding
of chunked is used, for which the terminal zero-length chunk has been
received. A response that has neither chunked transfer coding nor
Content-Length is complete only if a valid closure alert has been
received. Treating an incomplete message as complete could expose
implementations to attack.
A client detecting an incomplete close SHOULD recover gracefully. It A client detecting an incomplete close SHOULD recover gracefully.
MAY resume a TLS session closed in this fashion.
Clients MUST send a closure alert before closing the connection. Clients MUST send a closure alert before closing the connection.
Clients which are unprepared to receive any more data MAY choose not Clients that do not expect to receive any more data MAY choose not to
to wait for the server's closure alert and simply close the wait for the server's closure alert and simply close the connection,
connection, thus generating an incomplete close on the server side. thus generating an incomplete close on the server side.
2.2.2. Server Behavior
RFC 2616 permits an HTTP client to close the connection at any time,
and requires servers to recover gracefully. In particular, servers
SHOULD be prepared to receive an incomplete close from the client,
since the client can often determine when the end of server data is.
Servers SHOULD be willing to resume TLS sessions closed in this
fashion.
Implementation note: In HTTP implementations which do not use Servers SHOULD be prepared to receive an incomplete close from the
persistent connections, the server ordinarily expects to be able to client, since the client can often determine when the end of server
signal end of data by closing the connection. When Content-Length is data is.
used, however, the client may have already sent the closure alert and
dropped the connection.
Servers MUST attempt to initiate an exchange of closure alerts with Servers MUST attempt to initiate an exchange of closure alerts with
the client before closing the connection. Servers MAY close the the client before closing the connection. Servers MAY close the
connection after sending the closure alert, thus generating an connection after sending the closure alert, thus generating an
incomplete close on the client side. incomplete close on the client side.
X. Enclosing Messages as Data 10. Enclosing Messages as Data
8.3.1. Internet Media Type message/http 10.1. Media Type message/http
The message/http type can be used to enclose a single HTTP request or The message/http media type can be used to enclose a single HTTP
response message, provided that it obeys the MIME restrictions for request or response message, provided that it obeys the MIME
all "message" types regarding line length and encodings. restrictions for all "message" types regarding line length and
encodings. Because of the line length limitations, field values
within message/http are allowed to use line folding (obs-fold), as
described in Section 5.2, to convey the field value over multiple
lines. A recipient of message/http data MUST replace any obsolete
line folding with one or more SP characters when the message is
consumed.
Type name: message Type name: message
Subtype name: http Subtype name: http
Required parameters: N/A Required parameters: N/A
Optional parameters: version, msgtype Optional parameters: version, msgtype
version: The HTTP-version number of the enclosed message (e.g., version: The HTTP-version number of the enclosed message (e.g.,
"1.1"). If not present, the version can be determined from the "1.1"). If not present, the version can be determined from the
first line of the body. first line of the body.
msgtype: The message type -- "request" or "response". If not msgtype: The message type - "request" or "response". If not
present, the type can be determined from the first line of the present, the type can be determined from the first line of the
body. body.
Encoding considerations: only "7bit", "8bit", or "binary" are Encoding considerations: only "7bit", "8bit", or "binary" are
permitted permitted
Security considerations: see Section 9 Security considerations: see Section 11
Interoperability considerations: N/A Interoperability considerations: N/A
Published specification: This specification (see Section 8.3.1). Published specification: This specification (see Section 10.1).
Applications that use this media type: N/A Applications that use this media type: N/A
Fragment identifier considerations: N/A Fragment identifier considerations: N/A
Additional information: Additional information: Magic number(s): N/A
Magic number(s): N/A
Deprecated alias names for this type: N/A Deprecated alias names for this type: N/A
File extension(s): N/A File extension(s): N/A
Macintosh file type code(s): N/A Macintosh file type code(s): N/A
Person and email address to contact for further information: Person and email address to contact for further information: See Aut
See Authors' Addresses section. hors' Addresses section.
Intended usage: COMMON Intended usage: COMMON
Restrictions on usage: N/A Restrictions on usage: N/A
Author: See Authors' Addresses section. Author: See Authors' Addresses section.
Change controller: IESG Change controller: IESG
8.3.2. Internet Media Type application/http 10.2. Media Type application/http
The application/http type can be used to enclose a pipeline of one or The application/http media type can be used to enclose a pipeline of
more HTTP request or response messages (not intermixed). one or more HTTP request or response messages (not intermixed).
Type name: application Type name: application
Subtype name: http Subtype name: http
Required parameters: N/A Required parameters: N/A
Optional parameters: version, msgtype Optional parameters: version, msgtype
version: The HTTP-version number of the enclosed messages (e.g., version: The HTTP-version number of the enclosed messages (e.g.,
"1.1"). If not present, the version can be determined from the "1.1"). If not present, the version can be determined from the
first line of the body. first line of the body.
msgtype: The message type -- "request" or "response". If not msgtype: The message type - "request" or "response". If not
present, the type can be determined from the first line of the present, the type can be determined from the first line of the
body. body.
Encoding considerations: HTTP messages enclosed by this type are in Encoding considerations: HTTP messages enclosed by this type are in
"binary" format; use of an appropriate Content-Transfer-Encoding "binary" format; use of an appropriate Content-Transfer-Encoding
is required when transmitted via email. is required when transmitted via email.
Security considerations: see Section 9 Security considerations: see Section 11
Interoperability considerations: N/A Interoperability considerations: N/A
Published specification: This specification (see Section 8.3.2). Published specification: This specification (see Section 10.2).
Applications that use this media type: N/A Applications that use this media type: N/A
Fragment identifier considerations: N/A Fragment identifier considerations: N/A
Additional information: Additional information: Deprecated alias names for this type: N/A
Deprecated alias names for this type: N/A
Magic number(s): N/A Magic number(s): N/A
File extension(s): N/A File extension(s): N/A
Macintosh file type code(s): N/A Macintosh file type code(s): N/A
Person and email address to contact for further information: Person and email address to contact for further information: See Aut
See Authors' Addresses section. hors' Addresses section.
Intended usage: COMMON Intended usage: COMMON
Restrictions on usage: N/A Restrictions on usage: N/A
Author: See Authors' Addresses section. Author: See Authors' Addresses section.
Change controller: IESG Change controller: IESG
9. Security Considerations 11. Security Considerations
This section is meant to inform developers, information providers, This section is meant to inform developers, information providers,
and users of known security considerations relevant to HTTP message and users about known security considerations relevant to HTTP
syntax, parsing, and routing. Security considerations about HTTP message syntax and parsing. Security considerations about HTTP
semantics and payloads are addressed in [RFC7231]. semantics, content, and routing are addressed in [HTTP].
9.4. Response Splitting 11.1. Response Splitting
Response splitting (a.k.a, CRLF injection) is a common technique, Response splitting (a.k.a., CRLF injection) is a common technique,
used in various attacks on Web usage, that exploits the line-based used in various attacks on Web usage, that exploits the line-based
nature of HTTP message framing and the ordered association of nature of HTTP message framing and the ordered association of
requests to responses on persistent connections [Klein]. This requests to responses on persistent connections [Klein]. This
technique can be particularly damaging when the requests pass through technique can be particularly damaging when the requests pass through
a shared cache. a shared cache.
Response splitting exploits a vulnerability in servers (usually Response splitting exploits a vulnerability in servers (usually
within an application server) where an attacker can send encoded data within an application server) where an attacker can send encoded data
within some parameter of the request that is later decoded and echoed within some parameter of the request that is later decoded and echoed
within any of the response header fields of the response. If the within any of the response header fields of the response. If the
skipping to change at line 1723 skipping to change at page 39, line 37
However, that assumes the application server is only performing URI However, that assumes the application server is only performing URI
decoding, rather than more obscure data transformations like charset decoding, rather than more obscure data transformations like charset
transcoding, XML entity translation, base64 decoding, sprintf transcoding, XML entity translation, base64 decoding, sprintf
reformatting, etc. A more effective mitigation is to prevent reformatting, etc. A more effective mitigation is to prevent
anything other than the server's core protocol libraries from sending anything other than the server's core protocol libraries from sending
a CR or LF within the header section, which means restricting the a CR or LF within the header section, which means restricting the
output of header fields to APIs that filter for bad octets and not output of header fields to APIs that filter for bad octets and not
allowing application servers to write directly to the protocol allowing application servers to write directly to the protocol
stream. stream.
9.5. Request Smuggling 11.2. Request Smuggling
Request smuggling ([Linhart]) is a technique that exploits Request smuggling ([Linhart]) is a technique that exploits
differences in protocol parsing among various recipients to hide differences in protocol parsing among various recipients to hide
additional requests (which might otherwise be blocked or disabled by additional requests (which might otherwise be blocked or disabled by
policy) within an apparently harmless request. Like response policy) within an apparently harmless request. Like response
splitting, request smuggling can lead to a variety of attacks on HTTP splitting, request smuggling can lead to a variety of attacks on HTTP
usage. usage.
This specification has introduced new requirements on request This specification has introduced new requirements on request
parsing, particularly with regard to message framing in parsing, particularly with regard to message framing in Section 6.3,
Section 3.3.3, to reduce the effectiveness of request smuggling. to reduce the effectiveness of request smuggling.
9.6. Message Integrity 11.3. Message Integrity
HTTP does not define a specific mechanism for ensuring message HTTP does not define a specific mechanism for ensuring message
integrity, instead relying on the error-detection ability of integrity, instead relying on the error-detection ability of
underlying transport protocols and the use of length or underlying transport protocols and the use of length or chunk-
chunk-delimited framing to detect completeness. Additional integrity delimited framing to detect completeness. Historically, the lack of
mechanisms, such as hash functions or digital signatures applied to a single integrity mechanism has been justified by the informal
the content, can be selectively added to messages via extensible nature of most HTTP communication. However, the prevalence of HTTP
metadata header fields. Historically, the lack of a single integrity as an information access mechanism has resulted in its increasing use
mechanism has been justified by the informal nature of most HTTP within environments where verification of message integrity is
communication. However, the prevalence of HTTP as an information crucial.
access mechanism has resulted in its increasing use within
environments where verification of message integrity is crucial.
User agents are encouraged to implement configurable means for The mechanisms provided with the "https" scheme, such as
detecting and reporting failures of message integrity such that those authenticated encryption, provide protection against modification of
means can be enabled within environments for which integrity is messages. Care is needed however to ensure that connection closure
necessary. For example, a browser being used to view medical history cannot be used to truncate messages (see Section 9.8). User agents
or drug interaction information needs to indicate to the user when might refuse to accept incomplete messages or treat them specially.
such information is detected by the protocol to be incomplete, For example, a browser being used to view medical history or drug
expired, or corrupted during transfer. Such mechanisms might be interaction information needs to indicate to the user when such
selectively enabled via user agent extensions or the presence of information is detected by the protocol to be incomplete, expired, or
message integrity metadata in a response. At a minimum, user agents corrupted during transfer. Such mechanisms might be selectively
ought to provide some indication that allows a user to distinguish enabled via user agent extensions or the presence of message
between a complete and incomplete response message (Section 3.4) when integrity metadata in a response.
such verification is desired.
9.7. Message Confidentiality The "http" scheme provides no protection against accidental or
malicious modification of messages.
Extensions to the protocol might be used to mitigate the risk of
unwanted modification of messages by intermediaries, even when the
"https" scheme is used. Integrity might be assured by using message
authentication codes or digital signatures that are selectively added
to messages via extensible metadata fields.
11.4. Message Confidentiality
HTTP relies on underlying transport protocols to provide message HTTP relies on underlying transport protocols to provide message
confidentiality when that is desired. HTTP has been specifically confidentiality when that is desired. HTTP has been specifically
designed to be independent of the transport protocol, such that it designed to be independent of the transport protocol, such that it
can be used over many different forms of encrypted connection, with can be used over many forms of encrypted connection, with the
the selection of such transports being identified by the choice of selection of such transports being identified by the choice of URI
URI scheme or within user agent configuration. scheme or within user agent configuration.
The "https" scheme can be used to identify resources that require a The "https" scheme can be used to identify resources that require a
confidential connection, as described in Section 2.7.2. confidential connection, as described in Section 4.2.2 of [HTTP].
12. IANA Considerations 12. IANA Considerations
The change controller is: "IETF (iesg@ietf.org) - Internet The change controller for the following registrations is: "IETF
Engineering Task Force". (iesg@ietf.org) - Internet Engineering Task Force".
12.1. Header Field Registration
HTTP header fields are registered within the "Message Headers" 12.1. Field Name Registration
registry maintained at
<http://www.iana.org/assignments/message-headers/>.
, so the
"Permanent Message Header Field Names" registry has been updated
accordingly (see [BCP90])
This document defines the following HTTP header fields. First, introduce the new "Hypertext Transfer Protocol (HTTP) Field
Name Registry" at <https://www.iana.org/assignments/http-fields> as
described in Section 18.4 of [HTTP].
+-------------------+----------+----------+---------------+ Then, please update the registry with the field names listed in the
| Header Field Name | Protocol | Status | Reference | table below:
+-------------------+----------+----------+---------------+
| MIME-Version | http | standard | Appendix A.1 |
| Transfer-Encoding | http | standard | Section 3.3.1 |
+-------------------+----------+----------+---------------+
Furthermore, the header field-name "Close" has been registered as +===================+==========+======+============+
"reserved", since using that name as an HTTP header field might | Field Name | Status | Ref. | Comments |
conflict with the "close" connection option of the Connection header +===================+==========+======+============+
field (Section 6.1). | Close | standard | 9.6 | (reserved) |
+-------------------+----------+------+------------+
| MIME-Version | standard | B.1 | |
+-------------------+----------+------+------------+
| Transfer-Encoding | standard | 6.1 | |
+-------------------+----------+------+------------+
+-------------------+----------+----------+------------+ Table 1
| Header Field Name | Protocol | Status | Reference |
+-------------------+----------+----------+------------+
| Close | http | reserved | Section 8.1 |
+-------------------+----------+----------+------------+
12.2. Media Type Registration 12.2. Media Type Registration
IANA maintains the registry of Internet media types [BCP13] at Please update the "Media Types" registry at
<http://www.iana.org/assignments/media-types>. <https://www.iana.org/assignments/media-types> with the registration
information in Section 10.1 and Section 10.2 for the media types
This document serves as the specification for the Internet media "message/http" and "application/http", respectively.
types "message/http" and "application/http". The following has been
registered with IANA.
12.3. Transfer Coding Registration 12.3. Transfer Coding Registration
The "HTTP Transfer Coding Registry" has been updated with the Please update the "HTTP Transfer Coding Registry" at
registrations below: <https://www.iana.org/assignments/http-parameters/> with the
registration procedure of Section 7.3 and the content coding names
summarized in the table below.
+------------+--------------------------------------+---------------+ +============+===============================+===========+
| Name | Description | Reference | | Name | Description | Reference |
+------------+--------------------------------------+---------------+ +============+===============================+===========+
| chunked | Transfer in a series of chunks | Section 4.1 | | chunked | Transfer in a series of | Section |
| compress | UNIX "compress" data format [Welch] | Section 4.2.1 | | | chunks | 7.1 |
| deflate | "deflate" compressed data | Section 4.2.2 | +------------+-------------------------------+-----------+
| | ([RFC1951]) inside the "zlib" data | | | compress | UNIX "compress" data format | Section |
| | format ([RFC1950]) | | | | [Welch] | 7.2 |
| gzip | GZIP file format [RFC1952] | Section 4.2.3 | +------------+-------------------------------+-----------+
| x-compress | Deprecated (alias for compress) | Section 4.2.1 | | deflate | "deflate" compressed data | Section |
| x-gzip | Deprecated (alias for gzip) | Section 4.2.3 | | | ([RFC1951]) inside the "zlib" | 7.2 |
+------------+--------------------------------------+---------------+ | | data format ([RFC1950]) | |
+------------+-------------------------------+-----------+
| gzip | GZIP file format [RFC1952] | Section |
| | | 7.2 |
+------------+-------------------------------+-----------+
| trailers | (reserved) | Section |
| | | 12.3 |
+------------+-------------------------------+-----------+
| x-compress | Deprecated (alias for | Section |
| | compress) | 7.2 |
+------------+-------------------------------+-----------+
| x-gzip | Deprecated (alias for gzip) | Section |
| | | 7.2 |
+------------+-------------------------------+-----------+
12.4. [new] Table 2
[new] | *Note:* the coding name "trailers" is reserved because its use
| would conflict with the keyword "trailers" in the TE header
| field (Section 10.1.4 of [HTTP]).
[new] 12.4. ALPN Protocol ID Registration
[new] Please update the "TLS Application-Layer Protocol Negotiation (ALPN)
Protocol IDs" registry at <https://www.iana.org/assignments/tls-
extensiontype-values/tls-extensiontype-values.xhtml> with the
registration below:
+==========+=============================+================+
| Protocol | Identification Sequence | Reference |
+==========+=============================+================+
| HTTP/1.1 | 0x68 0x74 0x74 0x70 0x2f | (this |
| | 0x31 0x2e 0x31 ("http/1.1") | specification) |
+----------+-----------------------------+----------------+
Table 3
13. References 13. References
13.1. Normative References 13.1. Normative References
[RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB Compressed Data [CACHING] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Format Specification version 3.3", RFC 1950, May 1996. Ed., "HTTP Caching", Work in Progress, Internet-Draft,
draft-ietf-httpbis-cache-19, 10 September 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
cache-19>.
[RFC1951] Deutsch, P., "DEFLATE Compressed Data Format [HTTP] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Specification version 1.3", RFC 1951, May 1996. Ed., "HTTP Semantics", Work in Progress, Internet-Draft,
draft-ietf-httpbis-semantics-19, 10 September 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
semantics-19>.
[RFC1952] Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L., and [RFC1950] Deutsch, L.P. and J-L. Gailly, "ZLIB Compressed Data
G. Randers-Pehrson, "GZIP file format specification Format Specification version 3.3", RFC 1950,
version 4.3", RFC 1952, May 1996. DOI 10.17487/RFC1950, May 1996,
<https://www.rfc-editor.org/info/rfc1950>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC1951] Deutsch, P., "DEFLATE Compressed Data Format Specification
Requirement Levels", BCP 14, RFC 2119, March 1997. version 1.3", RFC 1951, DOI 10.17487/RFC1951, May 1996,
<https://www.rfc-editor.org/info/rfc1951>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, [RFC1952] Deutsch, P., Gailly, J-L., Adler, M., Deutsch, L.P., and
"Uniform Resource Identifier (URI): Generic Syntax", G. Randers-Pehrson, "GZIP file format specification
STD 66, RFC 3986, January 2005. version 4.3", RFC 1952, DOI 10.17487/RFC1952, May 1996,
<https://www.rfc-editor.org/info/rfc1952>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Syntax Specifications: ABNF", STD 68, RFC 5234, Requirement Levels", BCP 14, RFC 2119,
January 2008. DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Transfer Protocol (HTTP/1.1): Semantics and Content", Specifications: ABNF", STD 68, RFC 5234,
RFC 7231, June 2014. DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[RFC7232] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext [RFC7405] Kyzivat, P., "Case-Sensitive String Support in ABNF",
Transfer Protocol (HTTP/1.1): Conditional Requests", RFC 7405, DOI 10.17487/RFC7405, December 2014,
RFC 7232, June 2014. <https://www.rfc-editor.org/info/rfc7405>.
[RFC7233] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed., [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
"Hypertext Transfer Protocol (HTTP/1.1): Range 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
Requests", RFC 7233, June 2014. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC7234] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, [TLS13] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Ed., "Hypertext Transfer Protocol (HTTP/1.1): Caching", Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
RFC 7234, June 2014. <https://www.rfc-editor.org/info/rfc8446>.
[RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext [URI] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Transfer Protocol (HTTP/1.1): Authentication", Resource Identifier (URI): Generic Syntax", STD 66,
RFC 7235, June 2014. RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[USASCII] American National Standards Institute, "Coded Character [USASCII] American National Standards Institute, "Coded Character
Set -- 7-bit American Standard Code for Information Set -- 7-bit American Standard Code for Information
Interchange", ANSI X3.4, 1986. Interchange", ANSI X3.4, 1986.
[Welch] Welch, T., "A Technique for High-Performance Data [Welch] Welch, T. A., "A Technique for High-Performance Data
Compression", IEEE Computer 17(6), June 1984. Compression", IEEE Computer 17(6), June 1984.
13.2. Informative References 13.2. Informative References
[BCP13] Freed, N., Klensin, J., and T. Hansen, "Media Type [Err4667] RFC Errata, Erratum ID 4667, RFC 7230,
Specifications and Registration Procedures", BCP 13, <https://www.rfc-editor.org/errata/eid4667>.
RFC 6838, January 2013.
[BCP90] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90,
RFC 3864, September 2004.
[ISO-8859-1] International Organization for Standardization,
"Information technology -- 8-bit single-byte coded
graphic character sets -- Part 1: Latin alphabet No.
1", ISO/IEC 8859-1:1998, 1998.
[Klein] Klein, A., "Divide and Conquer - HTTP Response
Splitting, Web Cache Poisoning Attacks, and Related
Topics", March 2004, <http://packetstormsecurity.com/
papers/general/whitepaper_httpresponse.pdf>.
[Kri2001] Kristol, D., "HTTP Cookies: Standards, Privacy, and [HTTP/1.0] Berners-Lee, T., Fielding, R.T., and H.F. Nielsen,
Politics", ACM Transactions on Internet "Hypertext Transfer Protocol -- HTTP/1.0", RFC 1945,
Technology 1(2), November 2001, DOI 10.17487/RFC1945, May 1996,
<http://arxiv.org/abs/cs.SE/0105018>. <https://www.rfc-editor.org/info/rfc1945>.
[Linhart] Linhart, C., Klein, A., Heled, R., and S. Orrin, "HTTP [Klein] Klein, A., "Divide and Conquer - HTTP Response Splitting,
Request Smuggling", June 2005, Web Cache Poisoning Attacks, and Related Topics", March
<http://www.watchfire.com/news/whitepapers.aspx>. 2004, <https://packetstormsecurity.com/papers/general/
whitepaper_httpresponse.pdf>.
[RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen, [Linhart] Linhart, C., Klein, A., Heled, R., and S. Orrin, "HTTP
"Hypertext Transfer Protocol -- HTTP/1.0", RFC 1945, Request Smuggling", June 2005,
May 1996. <https://www.cgisecurity.com/lib/HTTP-Request-
Smuggling.pdf>.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet [RFC2045] Freed, N. and N.S. Borenstein, "Multipurpose Internet Mail
Mail Extensions (MIME) Part One: Format of Internet Extensions (MIME) Part One: Format of Internet Message
Message Bodies", RFC 2045, November 1996. Bodies", RFC 2045, DOI 10.17487/RFC2045, November 1996,
<https://www.rfc-editor.org/info/rfc2045>.
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail [RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046, Extensions (MIME) Part Two: Media Types", RFC 2046,
November 1996. DOI 10.17487/RFC2046, November 1996,
<https://www.rfc-editor.org/info/rfc2046>.
[RFC2047] Moore, K., "MIME (Multipurpose Internet Mail
Extensions) Part Three: Message Header Extensions for
Non-ASCII Text", RFC 2047, November 1996.
[RFC2049] Freed, N. and N. Borenstein, "Multipurpose Internet Mail [RFC2049] Freed, N. and N.S. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Five: Conformance Criteria and Extensions (MIME) Part Five: Conformance Criteria and
Examples", RFC 2049, November 1996. Examples", RFC 2049, DOI 10.17487/RFC2049, November 1996,
<https://www.rfc-editor.org/info/rfc2049>.
[RFC2068] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and [RFC2068] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and T.
T. Berners-Lee, "Hypertext Transfer Protocol -- Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1",
HTTP/1.1", RFC 2068, January 1997. RFC 2068, DOI 10.17487/RFC2068, January 1997,
<https://www.rfc-editor.org/info/rfc2068>.
[RFC2557] Palme, F., Hopmann, A., Shelness, N., and E. Stefferud, [RFC2557] Palme, F., Hopmann, A., Shelness, N., and E. Stefferud,
"MIME Encapsulation of Aggregate Documents, such as HTML "MIME Encapsulation of Aggregate Documents, such as HTML
(MHTML)", RFC 2557, March 1999. (MHTML)", RFC 2557, DOI 10.17487/RFC2557, March 1999,
<https://www.rfc-editor.org/info/rfc2557>.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2817] Khare, R. and S. Lawrence, "Upgrading to TLS Within
HTTP/1.1", RFC 2817, May 2000.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing
an IANA Considerations Section in RFCs", BCP 26,
RFC 5226, May 2008.
[RFC5322] Resnick, P., "Internet Message Format", RFC 5322, [RFC5322] Resnick, P., "Internet Message Format", RFC 5322,
October 2008. DOI 10.17487/RFC5322, October 2008,
<https://www.rfc-editor.org/info/rfc5322>.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, [RFC7230] Fielding, R., Ed. and J. F. Reschke, Ed., "Hypertext
April 2011. Transfer Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>.
[RFC6585] Nottingham, M. and R. Fielding, "Additional HTTP Status [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Codes", RFC 6585, April 2012. Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
Appendix A. Collected ABNF Appendix A. Collected ABNF
BWS = OWS In the collected ABNF below, list rules are expanded as per
Section 5.6.1 of [HTTP].
Connection = *( "," OWS ) connection-option *( OWS "," [ OWS
connection-option ] )
Content-Length = 1*DIGIT BWS = <BWS, see [HTTP], Section 5.6.3>
HTTP-message = start-line *( header-field CRLF ) CRLF [ message-body HTTP-message = start-line CRLF *( field-line CRLF ) CRLF [
] message-body ]
HTTP-name = %x48.54.54.50 ; HTTP HTTP-name = %x48.54.54.50 ; HTTP
HTTP-version = HTTP-name "/" DIGIT "." DIGIT HTTP-version = HTTP-name "/" DIGIT "." DIGIT
Host = uri-host [ ":" port ]
OWS = *( SP / HTAB ) OWS = <OWS, see [HTTP], Section 5.6.3>
RWS = 1*( SP / HTAB )
TE = [ ( "," / t-codings ) *( OWS "," [ OWS t-codings ] ) ]
Trailer = *( "," OWS ) field-name *( OWS "," [ OWS field-name ] )
Transfer-Encoding = *( "," OWS ) transfer-coding *( OWS "," [ OWS
transfer-coding ] )
URI-reference = <URI-reference, see [RFC3986], Section 4.1> RWS = <RWS, see [HTTP], Section 5.6.3>
Upgrade = *( "," OWS ) protocol *( OWS "," [ OWS protocol ] )
Via = *( "," OWS ) ( received-protocol RWS received-by [ RWS comment Transfer-Encoding = [ transfer-coding *( OWS "," OWS transfer-coding
] ) *( OWS "," [ OWS ( received-protocol RWS received-by [ RWS ) ]
comment ] ) ] )
absolute-URI = <absolute-URI, see [RFC3986], Section 4.3> absolute-URI = <absolute-URI, see [URI], Section 4.3>
absolute-form = absolute-URI absolute-form = absolute-URI
absolute-path = 1*( "/" segment ) absolute-path = <absolute-path, see [HTTP], Section 4.1>
asterisk-form = "*" asterisk-form = "*"
authority = <authority, see [RFC3986], Section 3.2> authority = <authority, see [URI], Section 3.2>
authority-form = authority authority-form = uri-host ":" port
chunk = chunk-size [ chunk-ext ] CRLF chunk-data CRLF chunk = chunk-size [ chunk-ext ] CRLF chunk-data CRLF
chunk-data = 1*OCTET chunk-data = 1*OCTET
chunk-ext = *( ";" chunk-ext-name [ "=" chunk-ext-val ] ) chunk-ext = *( BWS ";" BWS chunk-ext-name [ BWS "=" BWS chunk-ext-val
] )
chunk-ext-name = token chunk-ext-name = token
chunk-ext-val = token / quoted-string chunk-ext-val = token / quoted-string
chunk-size = 1*HEXDIG chunk-size = 1*HEXDIG
chunked-body = *chunk last-chunk trailer-part CRLF chunked-body = *chunk last-chunk trailer-section CRLF
comment = "(" *( ctext / quoted-pair / comment ) ")"
connection-option = token
ctext = HTAB / SP / %x21-27 ; '!'-'''
/ %x2A-5B ; '*'-'['
/ %x5D-7E ; ']'-'~'
/ obs-text
field-content = field-vchar [ 1*( SP / HTAB ) field-vchar ]
field-name = token
field-value = *( field-content / obs-fold )
field-vchar = VCHAR / obs-text
fragment = <fragment, see [RFC3986], Section 3.5>
header-field = field-name ":" OWS field-value OWS field-line = field-name ":" OWS field-value OWS
http-URI = "http://" authority path-abempty [ "?" query ] [ "#" field-name = <field-name, see [HTTP], Section 5.1>
fragment ] field-value = <field-value, see [HTTP], Section 5.5>
https-URI = "https://" authority path-abempty [ "?" query ] [ "#"
fragment ]
last-chunk = 1*"0" [ chunk-ext ] CRLF last-chunk = 1*"0" [ chunk-ext ] CRLF
message-body = *OCTET message-body = *OCTET
method = token method = token
obs-fold = CRLF 1*( SP / HTAB ) obs-fold = OWS CRLF RWS
obs-text = %x80-FF obs-text = <obs-text, see [HTTP], Section 5.6.4>
origin-form = absolute-path [ "?" query ] origin-form = absolute-path [ "?" query ]
partial-URI = relative-part [ "?" query ] port = <port, see [URI], Section 3.2.3>
path-abempty = <path-abempty, see [RFC3986], Section 3.3>
port = <port, see [RFC3986], Section 3.2.3>
protocol = protocol-name [ "/" protocol-version ]
protocol-name = token
protocol-version = token
pseudonym = token
qdtext = HTAB / SP / "!" / %x23-5B ; '#'-'[' query = <query, see [URI], Section 3.4>
/ %x5D-7E ; ']'-'~' quoted-string = <quoted-string, see [HTTP], Section 5.6.4>
/ obs-text
query = <query, see [RFC3986], Section 3.4>
quoted-pair = "\" ( HTAB / SP / VCHAR / obs-text )
quoted-string = DQUOTE *( qdtext / quoted-pair ) DQUOTE
rank = ( "0" [ "." *3DIGIT ] ) / ( "1" [ "." *3"0" ] ) reason-phrase = 1*( HTAB / SP / VCHAR / obs-text )
reason-phrase = *( HTAB / SP / VCHAR / obs-text ) request-line = method SP request-target SP HTTP-version
received-by = ( uri-host [ ":" port ] ) / pseudonym
received-protocol = [ protocol-name "/" ] protocol-version
relative-part = <relative-part, see [RFC3986], Section 4.2>
request-line = method SP request-target SP HTTP-version CRLF
request-target = origin-form / absolute-form / authority-form / request-target = origin-form / absolute-form / authority-form /
asterisk-form asterisk-form
scheme = <scheme, see [RFC3986], Section 3.1>
segment = <segment, see [RFC3986], Section 3.3>
start-line = request-line / status-line start-line = request-line / status-line
status-code = 3DIGIT status-code = 3DIGIT
status-line = HTTP-version SP status-code SP reason-phrase CRLF status-line = HTTP-version SP status-code SP [ reason-phrase ]
t-codings = "trailers" / ( transfer-coding [ t-ranking ] ) token = <token, see [HTTP], Section 5.6.2>
t-ranking = OWS ";" OWS "q=" rank trailer-section = *( field-line CRLF )
tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." / transfer-coding = <transfer-coding, see [HTTP], Section 10.1.4>
"^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA
token = 1*tchar
trailer-part = *( header-field CRLF )
transfer-coding = "chunked" / "compress" / "deflate" / "gzip" /
transfer-extension
transfer-extension = token *( OWS ";" OWS transfer-parameter )
transfer-parameter = token BWS "=" BWS ( token / quoted-string )
uri-host = <host, see [RFC3986], Section 3.2.2> uri-host = <host, see [URI], Section 3.2.2>
Appendix B. Differences between HTTP and MIME Appendix B. Differences between HTTP and MIME
HTTP/1.1 uses many of the constructs defined for the Internet Message HTTP/1.1 uses many of the constructs defined for the Internet Message
Format [RFC5322] and the Multipurpose Internet Mail Extensions (MIME) Format [RFC5322] and the Multipurpose Internet Mail Extensions (MIME)
[RFC2045] to allow a message body to be transmitted in an open [RFC2045] to allow a message body to be transmitted in an open
variety of representations and with extensible header fields. variety of representations and with extensible fields. However, RFC
However, RFC 2045 is focused only on email; applications of HTTP have 2045 is focused only on email; applications of HTTP have many
many characteristics that differ from email; hence, HTTP has features characteristics that differ from email; hence, HTTP has features that
that differ from MIME. These differences were carefully chosen to differ from MIME. These differences were carefully chosen to
optimize performance over binary connections, to allow greater optimize performance over binary connections, to allow greater
freedom in the use of new media types, to make date comparisons freedom in the use of new media types, to make date comparisons
easier, and to acknowledge the practice of some early HTTP servers easier, and to acknowledge the practice of some early HTTP servers
and clients. and clients.
This appendix describes specific areas where HTTP differs from MIME. This appendix describes specific areas where HTTP differs from MIME.
Proxies and gateways to and from strict MIME environments need to be Proxies and gateways to and from strict MIME environments need to be
aware of these differences and provide the appropriate conversions aware of these differences and provide the appropriate conversions
where necessary. where necessary.
B.1. MIME-Version B.1. MIME-Version
HTTP is not a MIME-compliant protocol. However, messages can include HTTP is not a MIME-compliant protocol. However, messages can include
a single MIME-Version header field to indicate what version of the a single MIME-Version header field to indicate what version of the
MIME protocol was used to construct the message. Use of the MIME protocol was used to construct the message. Use of the MIME-
MIME-Version header field indicates that the message is in full Version header field indicates that the message is in full
conformance with the MIME protocol (as defined in [RFC2045]). conformance with the MIME protocol (as defined in [RFC2045]).
Senders are responsible for ensuring full conformance (where Senders are responsible for ensuring full conformance (where
possible) when exporting HTTP messages to strict MIME environments. possible) when exporting HTTP messages to strict MIME environments.
B.2. Conversion to Canonical Form B.2. Conversion to Canonical Form
MIME requires that an Internet mail body part be converted to MIME requires that an Internet mail body part be converted to
canonical form prior to being transferred, as described in Section 4 canonical form prior to being transferred, as described in Section 4
of [RFC2049]. Section 3.1.1.3 of this document describes the forms of [RFC2049], and that content with a type of "text" represent line
allowed for subtypes of the "text" media type when transmitted over breaks as CRLF, forbidding the use of CR or LF outside of line break
HTTP. [RFC2046] requires that content with a type of "text" sequences [RFC2046]. In contrast, HTTP does not care whether CRLF,
represent line breaks as CRLF and forbids the use of CR or LF outside bare CR, or bare LF are used to indicate a line break within content.
of line break sequences. HTTP allows CRLF, bare CR, and bare LF to
indicate a line break within text content.
A proxy or gateway from HTTP to a strict MIME environment ought to A proxy or gateway from HTTP to a strict MIME environment ought to
translate all line breaks within the text media types described in translate all line breaks within text media types to the RFC 2049
Section 3.1.1.3 of this document to the RFC 2049 canonical form of canonical form of CRLF. Note, however, this might be complicated by
CRLF. Note, however, this might be complicated by the presence of a the presence of a Content-Encoding and by the fact that HTTP allows
Content-Encoding and by the fact that HTTP allows the use of some the use of some charsets that do not use octets 13 and 10 to
charsets that do not use octets 13 and 10 to represent CR and LF, represent CR and LF, respectively.
respectively.
Conversion will break any cryptographic checksums applied to the Conversion will break any cryptographic checksums applied to the
original content unless the original content is already in canonical original content unless the original content is already in canonical
form. Therefore, the canonical form is recommended for any content form. Therefore, the canonical form is recommended for any content
that uses such checksums in HTTP. that uses such checksums in HTTP.
B.3. Conversion of Date Formats B.3. Conversion of Date Formats
HTTP/1.1 uses a restricted set of date formats (Section 7.1.1.1) to HTTP/1.1 uses a restricted set of date formats (Section 5.6.7 of
simplify the process of date comparison. Proxies and gateways from [HTTP]) to simplify the process of date comparison. Proxies and
other protocols ought to ensure that any Date header field present in gateways from other protocols ought to ensure that any Date header
a message conforms to one of the HTTP/1.1 formats and rewrite the field present in a message conforms to one of the HTTP/1.1 formats
date if necessary. and rewrite the date if necessary.
B.4. Conversion of Content-Encoding B.4. Conversion of Content-Encoding
MIME does not include any concept equivalent to HTTP/1.1's MIME does not include any concept equivalent to HTTP/1.1's Content-
Content-Encoding header field. Since this acts as a modifier on the Encoding header field. Since this acts as a modifier on the media
media type, proxies and gateways from HTTP to MIME-compliant type, proxies and gateways from HTTP to MIME-compliant protocols
protocols ought to either change the value of the Content-Type header ought to either change the value of the Content-Type header field or
field or decode the representation before forwarding the message. decode the representation before forwarding the message. (Some
(Some experimental applications of Content-Type for Internet mail experimental applications of Content-Type for Internet mail have used
have used a media-type parameter of ";conversions=<content-coding>" a media-type parameter of ";conversions=<content-coding>" to perform
to perform a function equivalent to Content-Encoding. However, this a function equivalent to Content-Encoding. However, this parameter
parameter is not part of the MIME standards). is not part of the MIME standards).
B.5. Conversion of Content-Transfer-Encoding B.5. Conversion of Content-Transfer-Encoding
HTTP does not use the Content-Transfer-Encoding field of MIME. HTTP does not use the Content-Transfer-Encoding field of MIME.
Proxies and gateways from MIME-compliant protocols to HTTP need to Proxies and gateways from MIME-compliant protocols to HTTP need to
remove any Content-Transfer-Encoding prior to delivering the response remove any Content-Transfer-Encoding prior to delivering the response
message to an HTTP client. message to an HTTP client.
Proxies and gateways from HTTP to MIME-compliant protocols are Proxies and gateways from HTTP to MIME-compliant protocols are
responsible for ensuring that the message is in the correct format responsible for ensuring that the message is in the correct format
skipping to change at line 2184 skipping to change at page 48, line 52
appropriate Content-Transfer-Encoding if doing so will improve the appropriate Content-Transfer-Encoding if doing so will improve the
likelihood of safe transport over the destination protocol. likelihood of safe transport over the destination protocol.
B.6. MHTML and Line Length Limitations B.6. MHTML and Line Length Limitations
HTTP implementations that share code with MHTML [RFC2557] HTTP implementations that share code with MHTML [RFC2557]
implementations need to be aware of MIME line length limitations. implementations need to be aware of MIME line length limitations.
Since HTTP does not have this limitation, HTTP does not fold long Since HTTP does not have this limitation, HTTP does not fold long
lines. MHTML messages being transported by HTTP follow all lines. MHTML messages being transported by HTTP follow all
conventions of MHTML, including line length limitations and folding, conventions of MHTML, including line length limitations and folding,
canonicalization, etc., since HTTP transfers message-bodies as canonicalization, etc., since HTTP transfers message-bodies without
payload and, aside from the "multipart/byteranges" type (Appendix A modification and, aside from the "multipart/byteranges" type
of [RFC7233]), does not interpret the content or any MIME header (Section 14.6 of [HTTP]), does not interpret the content or any MIME
lines that might be contained therein. header lines that might be contained therein.
Appendix C. HTTP Version History
HTTP/1.1 remains compatible with HTTP/1.0 by including more stringent
requirements that enable reliable implementations, adding only those
features that can either be safely ignored by an HTTP/1.0 recipient
or only be sent when communicating with a party advertising
conformance with HTTP/1.1.
HTTP/1.1 has been designed to make supporting previous versions easy. Appendix C. Changes from previous RFCs
A general-purpose HTTP/1.1 server ought to be able to understand any
valid request in the format of HTTP/1.0, responding appropriately
with an HTTP/1.1 message that only uses features understood (or
safely ignored) by HTTP/1.0 clients. Likewise, an HTTP/1.1 client
can be expected to understand any valid HTTP/1.0 response.
C.1. Changes from HTTP/0.9 C.1. Changes from HTTP/0.9
Since HTTP/0.9 did not support header fields in a request, there is Since HTTP/0.9 did not support header fields in a request, there is
no mechanism for it to support name-based virtual hosts (selection of no mechanism for it to support name-based virtual hosts (selection of
resource by inspection of the Host header field). Any server that resource by inspection of the Host header field). Any server that
implements name-based virtual hosts ought to disable support for implements name-based virtual hosts ought to disable support for
HTTP/0.9. Most requests that appear to be HTTP/0.9 are, in fact, HTTP/0.9. Most requests that appear to be HTTP/0.9 are, in fact,
badly constructed HTTP/1.x requests caused by a client failing to badly constructed HTTP/1.x requests caused by a client failing to
properly encode the request-target. properly encode the request-target.
C.2. Changes from HTTP/1.0 C.2. Changes from HTTP/1.0
This section summarizes major differences between versions HTTP/1.0
and HTTP/1.1.
C.2.1. Multihomed Web Servers C.2.1. Multihomed Web Servers
The requirements that clients and servers support the Host header The requirements that clients and servers support the Host header
field (Section 5.4), report an error if it is missing from an field (Section 7.2 of [HTTP]), report an error if it is missing from
HTTP/1.1 request, and accept absolute URIs (Section 5.3) are among an HTTP/1.1 request, and accept absolute URIs (Section 3.2) are among
the most important changes defined by HTTP/1.1. the most important changes defined by HTTP/1.1.
Older HTTP/1.0 clients assumed a one-to-one relationship of IP Older HTTP/1.0 clients assumed a one-to-one relationship of IP
addresses and servers; there was no other established mechanism for addresses and servers; there was no other established mechanism for
distinguishing the intended server of a request than the IP address distinguishing the intended server of a request than the IP address
to which that request was directed. The Host header field was to which that request was directed. The Host header field was
introduced during the development of HTTP/1.1 and, though it was introduced during the development of HTTP/1.1 and, though it was
quickly implemented by most HTTP/1.0 browsers, additional quickly implemented by most HTTP/1.0 browsers, additional
requirements were placed on all HTTP/1.1 requests in order to ensure requirements were placed on all HTTP/1.1 requests in order to ensure
complete adoption. At the time of this writing, most HTTP-based complete adoption. At the time of this writing, most HTTP-based
services are dependent upon the Host header field for targeting services are dependent upon the Host header field for targeting
requests. requests.
C.2.2. Keep-Alive Connections C.2.2. Keep-Alive Connections
In HTTP/1.0, each connection is established by the client prior to In HTTP/1.0, each connection is established by the client prior to
the request and closed by the server after sending the response. the request and closed by the server after sending the response.
However, some implementations implement the explicitly negotiated However, some implementations implement the explicitly negotiated
("Keep-Alive") version of persistent connections described in Section ("Keep-Alive") version of persistent connections described in
19.7.1 of [RFC2068]. Section 19.7.1 of [RFC2068].
Some clients and servers might wish to be compatible with these Some clients and servers might wish to be compatible with these
previous approaches to persistent connections, by explicitly previous approaches to persistent connections, by explicitly
negotiating for them with a "Connection: keep-alive" request header negotiating for them with a "Connection: keep-alive" request header
field. However, some experimental implementations of HTTP/1.0 field. However, some experimental implementations of HTTP/1.0
persistent connections are faulty; for example, if an HTTP/1.0 proxy persistent connections are faulty; for example, if an HTTP/1.0 proxy
server doesn't understand Connection, it will erroneously forward server doesn't understand Connection, it will erroneously forward
that header field to the next inbound server, which would result in a that header field to the next inbound server, which would result in a
hung connection. hung connection.
One attempted solution was the introduction of a Proxy-Connection One attempted solution was the introduction of a Proxy-Connection
header field, targeted specifically at proxies. In practice, this header field, targeted specifically at proxies. In practice, this
was also unworkable, because proxies are often deployed in multiple was also unworkable, because proxies are often deployed in multiple
layers, bringing about the same problem discussed above. layers, bringing about the same problem discussed above.
As a result, clients are encouraged not to send the Proxy-Connection As a result, clients are encouraged not to send the Proxy-Connection
header field in any requests. header field in any requests.
Clients are also encouraged to consider the use of Connection: Clients are also encouraged to consider the use of Connection: keep-
keep-alive in requests carefully; while they can enable persistent alive in requests carefully; while they can enable persistent
connections with HTTP/1.0 servers, clients using them will need to connections with HTTP/1.0 servers, clients using them will need to
monitor the connection for "hung" requests (which indicate that the monitor the connection for "hung" requests (which indicate that the
client ought stop sending the header field), and this mechanism ought client ought to stop sending the header field), and this mechanism
not be used by clients at all when a proxy is being used. ought not be used by clients at all when a proxy is being used.
C.2.3. Introduction of Transfer-Encoding C.2.3. Introduction of Transfer-Encoding
HTTP/1.1 introduces the Transfer-Encoding header field HTTP/1.1 introduces the Transfer-Encoding header field (Section 6.1).
(Section 3.3.1). Transfer codings need to be decoded prior to Transfer codings need to be decoded prior to forwarding an HTTP
forwarding an HTTP message over a MIME-compliant protocol. message over a MIME-compliant protocol.
C.3. Changes from RFC 2616 C.3. Changes from RFC 7230
[elided] Most of the sections introducing HTTP's design goals, history,
architecture, conformance criteria, protocol versioning, URIs,
message routing, and header fields have been moved to [HTTP]. This
document has been reduced to just the messaging syntax and connection
management requirements specific to HTTP/1.1.
Bare CRs have been prohibited outside of content. (Section 2.2)
The ABNF definition of authority-form has changed from the more
general authority component of a URI (in which port is optional) to
the specific host:port format that is required by CONNECT.
(Section 3.2.3)
Required recipients to avoid smuggling/splitting attacks when
processing an ambiguous message framing. (Section 6.1)
In the ABNF for chunked extensions, re-introduced (bad) whitespace
around ";" and "=". Whitespace was removed in [RFC7230], but that
change was found to break existing implementations (see [Err4667]).
(Section 7.1.1)
Trailer field semantics now transcend the specifics of chunked
encoding. The decoding algorithm for chunked (Section 7.1.3) has
been updated to encourage storage/forwarding of trailer fields
separately from the header section, to only allow merging into the
header section if the recipient knows the corresponding field
definition permits and defines how to merge, and otherwise to discard
the trailer fields instead of merging. The trailer part is now
called the trailer section to be more consistent with the header
section and more distinct from a body part. (Section 7.1.2)
Disallowed transfer coding parameters called "q" in order to avoid
conflicts with the use of ranks in the TE header field.
(Section 7.3)
Appendix D. Change Log Appendix D. Change Log
This section is to be removed before publishing as an RFC.
D.1. Between RFC7230 and draft 00 D.1. Between RFC7230 and draft 00
The changes were purely editorial:
* Change boilerplate and abstract to indicate the "draft" status,
and update references to ancestor specifications.
* Adjust historical notes.
* Update links to sibling specifications.
* Replace sections listing changes from RFC 2616 by new empty
sections referring to RFC 723x.
* Remove acknowledgements specific to RFC 723x.
* Move "Acknowledgements" to the very end and make them unnumbered.
D.2. Since draft-ietf-httpbis-messaging-00 D.2. Since draft-ietf-httpbis-messaging-00
The changes in this draft are editorial, with respect to HTTP as a
whole, to move all core HTTP semantics into [HTTP]:
* Moved introduction, architecture, conformance, and ABNF extensions
from RFC 7230 (Messaging) to semantics [HTTP].
* Moved discussion of MIME differences from RFC 7231 (Semantics) to
Appendix B since they mostly cover transforming 1.1 messages.
* Moved all extensibility tips, registration procedures, and
registry tables from the IANA considerations to normative
sections, reducing the IANA considerations to just instructions
that will be removed prior to publication as an RFC.
D.3. Since draft-ietf-httpbis-messaging-01 D.3. Since draft-ietf-httpbis-messaging-01
* Cite RFC 8126 instead of RFC 5226 (<https://github.com/httpwg/
http-core/issues/75>)
* Resolved erratum 4779, no change needed here
(<https://github.com/httpwg/http-core/issues/87>,
<https://www.rfc-editor.org/errata/eid4779>)
* In Section 7, fixed prose claiming transfer parameters allow bare
names (<https://github.com/httpwg/http-core/issues/88>,
<https://www.rfc-editor.org/errata/eid4839>)
* Resolved erratum 4225, no change needed here
(<https://github.com/httpwg/http-core/issues/90>,
<https://www.rfc-editor.org/errata/eid4225>)
* Replace "response code" with "response status code"
(<https://github.com/httpwg/http-core/issues/94>,
<https://www.rfc-editor.org/errata/eid4050>)
* In Section 9.3, clarify statement about HTTP/1.0 keep-alive
(<https://github.com/httpwg/http-core/issues/96>,
<https://www.rfc-editor.org/errata/eid4205>)
* In Section 7.1.1, re-introduce (bad) whitespace around ";" and "="
(<https://github.com/httpwg/http-core/issues/101>,
<https://www.rfc-editor.org/errata/eid4667>, <https://www.rfc-
editor.org/errata/eid4825>)
* In Section 7.3, state that transfer codings should not use
parameters named "q" (<https://github.com/httpwg/http-core/
issues/15>, <https://www.rfc-editor.org/errata/eid4683>)
* In Section 7, mark coding name "trailers" as reserved in the IANA
registry (<https://github.com/httpwg/http-core/issues/108>)
D.4. Since draft-ietf-httpbis-messaging-02 D.4. Since draft-ietf-httpbis-messaging-02
* In Section 4, explain why the reason phrase should be ignored by
clients (<https://github.com/httpwg/http-core/issues/60>).
* Add Section 9.2 to explain how request/response correlation is
performed (<https://github.com/httpwg/http-core/issues/145>)
D.5. Since draft-ietf-httpbis-messaging-03 D.5. Since draft-ietf-httpbis-messaging-03
* In Section 9.2, caution against treating data on a connection as
part of a not-yet-issued request (<https://github.com/httpwg/http-
core/issues/26>)
* In Section 7, remove the predefined codings from the ABNF and make
it generic instead (<https://github.com/httpwg/http-core/
issues/66>)
* Use RFC 7405 ABNF notation for case-sensitive string constants
(<https://github.com/httpwg/http-core/issues/133>)
D.6. Since draft-ietf-httpbis-messaging-04 D.6. Since draft-ietf-httpbis-messaging-04
* In Section 7.8 of [HTTP], clarify that protocol-name is to be
matched case-insensitively (<https://github.com/httpwg/http-core/
issues/8>)
* In Section 5.2, add leading optional whitespace to obs-fold ABNF
(<https://github.com/httpwg/http-core/issues/19>,
<https://www.rfc-editor.org/errata/eid4189>)
* In Section 4, add clarifications about empty reason phrases
(<https://github.com/httpwg/http-core/issues/197>)
* Move discussion of retries from Section 9.3.1 into [HTTP]
(<https://github.com/httpwg/http-core/issues/230>)
D.7. Since draft-ietf-httpbis-messaging-05 D.7. Since draft-ietf-httpbis-messaging-05
* In Section 7.1.2, the trailer part has been renamed the trailer
section (for consistency with the header section) and trailers are
no longer merged as header fields by default, but rather can be
discarded, kept separate from header fields, or merged with header
fields only if understood and defined as being mergeable
(<https://github.com/httpwg/http-core/issues/16>)
* In Section 2.1 and related Sections, move the trailing CRLF from
the line grammars into the message format
(<https://github.com/httpwg/http-core/issues/62>)
* Moved Section 2.3 down (<https://github.com/httpwg/http-core/
issues/68>)
* In Section 7.8 of [HTTP], use 'websocket' instead of 'HTTP/2.0' in
examples (<https://github.com/httpwg/http-core/issues/112>)
* Move version non-specific text from Section 6 into semantics as
"payload" (<https://github.com/httpwg/http-core/issues/159>)
* In Section 9.8, add text from RFC 2818
(<https://github.com/httpwg/http-core/issues/236>)
D.8. Since draft-ietf-httpbis-messaging-06 D.8. Since draft-ietf-httpbis-messaging-06
* In Section 12.4, update the ALPN protocol ID for HTTP/1.1
(<https://github.com/httpwg/http-core/issues/49>)
* In Section 5, align with updates to field terminology in semantics
(<https://github.com/httpwg/http-core/issues/111>)
* In Section 7.6.1 of [HTTP], clarify that new connection options
indeed need to be registered (<https://github.com/httpwg/http-
core/issues/285>)
* In Section 1.1, reference RFC 8174 as well
(<https://github.com/httpwg/http-core/issues/303>)
D.9. Since draft-ietf-httpbis-messaging-07 D.9. Since draft-ietf-httpbis-messaging-07
* Move TE: trailers into [HTTP] (<https://github.com/httpwg/http-
core/issues/18>)
* In Section 6.3, adjust requirements for handling multiple content-
length values (<https://github.com/httpwg/http-core/issues/59>)
* Throughout, replace "effective request URI" with "target URI"
(<https://github.com/httpwg/http-core/issues/259>)
* In Section 6.1, don't claim Transfer-Encoding is supported by
HTTP/2 or later (<https://github.com/httpwg/http-core/issues/297>)
D.10. Since draft-ietf-httpbis-messaging-08 D.10. Since draft-ietf-httpbis-messaging-08
* In Section 2.2, disallow bare CRs (<https://github.com/httpwg/
http-core/issues/31>)
* Appendix A now uses the sender variant of the "#" list expansion
(<https://github.com/httpwg/http-core/issues/192>)
* In Section 5, adjust IANA "Close" entry for new registry format
(<https://github.com/httpwg/http-core/issues/273>)
D.11. Since draft-ietf-httpbis-messaging-09 D.11. Since draft-ietf-httpbis-messaging-09
* Switch to xml2rfc v3 mode for draft generation
(<https://github.com/httpwg/http-core/issues/394>)
D.12. Since draft-ietf-httpbis-messaging-10 D.12. Since draft-ietf-httpbis-messaging-10
* In Section 6.3, note that TCP half-close does not delimit a
request; talk about corresponding server-side behaviour in
Section 9.6 (<https://github.com/httpwg/http-core/issues/22>)
* Moved requirements specific to HTTP/1.1 from [HTTP] into
Section 3.2 (<https://github.com/httpwg/http-core/issues/182>)
* In Section 6.1 (Transfer-Encoding), adjust ABNF to allow empty
lists (<https://github.com/httpwg/http-core/issues/210>)
* In Section 9.7, add text from RFC 2818
(<https://github.com/httpwg/http-core/issues/236>)
* Moved definitions of "TE" and "Upgrade" into [HTTP]
(<https://github.com/httpwg/http-core/issues/392>)
* Moved definition of "Connection" into [HTTP]
(<https://github.com/httpwg/http-core/issues/407>)
D.13. Since draft-ietf-httpbis-messaging-11 D.13. Since draft-ietf-httpbis-messaging-11
* Move IANA Upgrade Token Registry instructions to [HTTP]
(<https://github.com/httpwg/http-core/issues/450>)
D.14. Since draft-ietf-httpbis-messaging-12 D.14. Since draft-ietf-httpbis-messaging-12
* Moved content of history appendix to Semantics
(<https://github.com/httpwg/http-core/issues/451>)
* Moved note about "close" being reserved as field name to
Section 9.3 (<https://github.com/httpwg/http-core/issues/500>)
* Moved table of transfer codings into Section 12.3
(<https://github.com/httpwg/http-core/issues/506>)
* In Section 13.2, updated the URI for the [Linhart] paper
(<https://github.com/httpwg/http-core/issues/517>)
* Changed document title to just "HTTP/1.1"
(<https://github.com/httpwg/http-core/issues/524>)
* In Section 7, moved transfer-coding ABNF to Section 10.1.4 of
[HTTP] (<https://github.com/httpwg/http-core/issues/531>)
* Changed to using "payload data" when defining requirements about
the data being conveyed within a message, instead of the terms
"payload body" or "response body" or "representation body", since
they often get confused with the HTTP/1.1 message body (which
includes transfer coding) (<https://github.com/httpwg/http-core/
issues/553>)
D.15. Since draft-ietf-httpbis-messaging-13 D.15. Since draft-ietf-httpbis-messaging-13
* In Section 6.3, clarify that a message needs to be checked for
both Content-Length and Transfer-Encoding, before processing
Transfer-Encoding, and that ought to be treated as an error, but
an intermediary can choose to forward the message downstream after
removing the Content-Length and processing the Transfer-Encoding
(<https://github.com/httpwg/http-core/issues/617>)
* Changed to using "content" instead of "payload" or "payload data"
to avoid confusion with the payload of version-specific messaging
frames (<https://github.com/httpwg/http-core/issues/654>)
D.16. Since draft-ietf-httpbis-messaging-14 D.16. Since draft-ietf-httpbis-messaging-14
* In Section 9.6, define the close connection option, since its
definition was removed from the Connection header field for being
specific to 1.1 (<https://github.com/httpwg/http-core/issues/678>)
* In Section 3.3, clarify how the target URI is reconstructed when
the request-target is not in absolute-form and highlight risk in
selecting a default host (<https://github.com/httpwg/http-core/
issues/722>)
* In Section 7.1, clarify large chunk handling issues
(<https://github.com/httpwg/http-core/issues/749>)
* In Section 2.2, explicitly close the connection after sending a
400 (<https://github.com/httpwg/http-core/issues/750>)
* In Section 2.3, refine version requirements for intermediaries
(<https://github.com/httpwg/http-core/issues/751>)
* In Section 7.1.3, don't remove the Trailer header field
(<https://github.com/httpwg/http-core/issues/793>)
* In Section 3.2.3, changed the ABNF definition of authority-form
from the authority component (in which port is optional) to the
host:port format that has always been required by CONNECT
(<https://github.com/httpwg/http-core/issues/806>)
D.17. Since draft-ietf-httpbis-messaging-15 D.17. Since draft-ietf-httpbis-messaging-15
* None.
D.18. Since draft-ietf-httpbis-messaging-16 D.18. Since draft-ietf-httpbis-messaging-16
This draft addresses mostly editorial issues raised during or past
IETF Last Call; see <https://github.com/httpwg/http-core/
issues?q=label%3Ah1-messaging+created%3A%3E2021-05-26> for a summary.
Furthermore:
* In Section 6.1, require recipients to avoid smuggling/splitting
attacks when processing an ambiguous message framing
(<https://github.com/httpwg/http-core/issues/879>)
D.19. Since draft-ietf-httpbis-messaging-17 D.19. Since draft-ietf-httpbis-messaging-17
Acknowledgments * In Section 4, rephrase text about status code definitions in
[HTTP] (<https://github.com/httpwg/http-core/issues/915>)
This edition of HTTP/1.1 builds on the many contributions that went * In Section 9.2, clarify how to match responses to requests
into RFC 1945, RFC 2068, RFC 2145, and RFC 2616, including (<https://github.com/httpwg/http-core/issues/915>)
substantial contributions made by the previous authors, editors, and
Working Group Chairs: Tim Berners-Lee, Ari Luotonen, Roy T. Fielding,
Henrik Frystyk Nielsen, Jim Gettys, Jeffrey C. Mogul, Larry Masinter,
and Paul J. Leach. Mark Nottingham oversaw this effort as Working
Group Chair.
Since 1999, the following contributors have helped improve the HTTP * Made reference to [RFC5322] normative, as it is referenced from
specification by reporting bugs, asking smart questions, drafting or the ABNF (for "From" header field) (<https://github.com/httpwg/
reviewing text, and evaluating open issues: http-core/issues/915>)
Adam Barth, Adam Roach, Addison Phillips, Adrian Chadd, Adrian Cole, * In Section 5.2, include text about message/http that previously
Adrien W. de Croy, Alan Ford, Alan Ruttenberg, Albert Lunde, Alek was in [HTTP] (<https://github.com/httpwg/http-core/issues/923>)
Storm, Alex Rousskov, Alexandre Morgaut, Alexey Melnikov, Alisha
Smith, Amichai Rothman, Amit Klein, Amos Jeffries, Andreas Maier,
Andreas Petersson, Andrei Popov, Anil Sharma, Anne van Kesteren,
Anthony Bryan, Asbjorn Ulsberg, Ashok Kumar, Balachander
Krishnamurthy, Barry Leiba, Ben Laurie, Benjamin Carlyle, Benjamin
Niven-Jenkins, Benoit Claise, Bil Corry, Bill Burke, Bjoern
Hoehrmann, Bob Scheifler, Boris Zbarsky, Brett Slatkin, Brian Kell,
Brian McBarron, Brian Pane, Brian Raymor, Brian Smith, Bruce Perens,
Bryce Nesbitt, Cameron Heavon-Jones, Carl Kugler, Carsten Bormann,
Charles Fry, Chris Burdess, Chris Newman, Christian Huitema, Cyrus
Daboo, Dale Robert Anderson, Dan Wing, Dan Winship, Daniel Stenberg,
Darrel Miller, Dave Cridland, Dave Crocker, Dave Kristol, Dave
Thaler, David Booth, David Singer, David W. Morris, Diwakar Shetty,
Dmitry Kurochkin, Drummond Reed, Duane Wessels, Edward Lee, Eitan
Adler, Eliot Lear, Emile Stephan, Eran Hammer-Lahav, Eric D.
Williams, Eric J. Bowman, Eric Lawrence, Eric Rescorla, Erik
Aronesty, EungJun Yi, Evan Prodromou, Felix Geisendoerfer, Florian
Weimer, Frank Ellermann, Fred Akalin, Fred Bohle, Frederic Kayser,
Gabor Molnar, Gabriel Montenegro, Geoffrey Sneddon, Gervase Markham,
Gili Tzabari, Grahame Grieve, Greg Slepak, Greg Wilkins, Grzegorz
Calkowski, Harald Tveit Alvestrand, Harry Halpin, Helge Hess, Henrik
Nordstrom, Henry S. Thompson, Henry Story, Herbert van de Sompel,
Herve Ruellan, Howard Melman, Hugo Haas, Ian Fette, Ian Hickson, Ido
Safruti, Ilari Liusvaara, Ilya Grigorik, Ingo Struck, J. Ross Nicoll,
James Cloos, James H. Manger, James Lacey, James M. Snell, Jamie
Lokier, Jan Algermissen, Jari Arkko, Jeff Hodges (who came up with
the term 'effective Request-URI'), Jeff Pinner, Jeff Walden, Jim
Luther, Jitu Padhye, Joe D. Williams, Joe Gregorio, Joe Orton, Joel
Jaeggli, John C. Klensin, John C. Mallery, John Cowan, John Kemp,
John Panzer, John Schneider, John Stracke, John Sullivan, Jonas
Sicking, Jonathan A. Rees, Jonathan Billington, Jonathan Moore,
Jonathan Silvera, Jordi Ros, Joris Dobbelsteen, Josh Cohen, Julien
Pierre, Jungshik Shin, Justin Chapweske, Justin Erenkrantz, Justin
James, Kalvinder Singh, Karl Dubost, Kathleen Moriarty, Keith
Hoffman, Keith Moore, Ken Murchison, Koen Holtman, Konstantin
Voronkov, Kris Zyp, Leif Hedstrom, Lionel Morand, Lisa Dusseault,
Maciej Stachowiak, Manu Sporny, Marc Schneider, Marc Slemko, Mark
Baker, Mark Pauley, Mark Watson, Markus Isomaki, Markus Lanthaler,
Martin J. Duerst, Martin Musatov, Martin Nilsson, Martin Thomson,
Matt Lynch, Matthew Cox, Matthew Kerwin, Max Clark, Menachem Dodge,
Meral Shirazipour, Michael Burrows, Michael Hausenblas, Michael
Scharf, Michael Sweet, Michael Tuexen, Michael Welzl, Mike Amundsen,
Mike Belshe, Mike Bishop, Mike Kelly, Mike Schinkel, Miles Sabin,
Murray S. Kucherawy, Mykyta Yevstifeyev, Nathan Rixham, Nicholas
Shanks, Nico Williams, Nicolas Alvarez, Nicolas Mailhot, Noah Slater,
Osama Mazahir, Pablo Castro, Pat Hayes, Patrick R. McManus, Paul E.
Jones, Paul Hoffman, Paul Marquess, Pete Resnick, Peter Lepeska,
Peter Occil, Peter Saint-Andre, Peter Watkins, Phil Archer, Phil
Hunt, Philippe Mougin, Phillip Hallam-Baker, Piotr Dobrogost, Poul-
Henning Kamp, Preethi Natarajan, Rajeev Bector, Ray Polk, Reto
Bachmann-Gmuer, Richard Barnes, Richard Cyganiak, Rob Trace, Robby
Simpson, Robert Brewer, Robert Collins, Robert Mattson, Robert
O'Callahan, Robert Olofsson, Robert Sayre, Robert Siemer, Robert de
Wilde, Roberto Javier Godoy, Roberto Peon, Roland Zink, Ronny
Widjaja, Ryan Hamilton, S. Mike Dierken, Salvatore Loreto, Sam
Johnston, Sam Pullara, Sam Ruby, Saurabh Kulkarni, Scott Lawrence
(who maintained the original issues list), Sean B. Palmer, Sean
Turner, Sebastien Barnoud, Shane McCarron, Shigeki Ohtsu, Simon
Yarde, Stefan Eissing, Stefan Tilkov, Stefanos Harhalakis, Stephane
Bortzmeyer, Stephen Farrell, Stephen Kent, Stephen Ludin, Stuart
Williams, Subbu Allamaraju, Subramanian Moonesamy, Susan Hares,
Sylvain Hellegouarch, Tapan Divekar, Tatsuhiro Tsujikawa, Tatsuya
Hayashi, Ted Hardie, Ted Lemon, Thomas Broyer, Thomas Fossati, Thomas
Maslen, Thomas Nadeau, Thomas Nordin, Thomas Roessler, Tim Bray, Tim
Morgan, Tim Olsen, Tom Zhou, Travis Snoozy, Tyler Close, Vincent
Murphy, Wenbo Zhu, Werner Baumann, Wilbur Streett, Wilfredo Sanchez
Vega, William A. Rowe Jr., William Chan, Willy Tarreau, Xiaoshu Wang,
Yaron Goland, Yngve Nysaeter Pettersen, Yoav Nir, Yogesh Bang,
Yuchung Cheng, Yutaka Oiwa, Yves Lafon (long-time member of the
editor team), Zed A. Shaw, and Zhong Yu.
See Section 16 of [RFC2616] for additional acknowledgements from * Throughout, disambiguate "selected representation" and "selected
prior revisions. response" (now "chosen response") (<https://github.com/httpwg/
http-core/issues/958>)
D.20. Since draft-ietf-httpbis-messaging-18
* Improve a few crossrefs into [HTTP] (<https://github.com/httpwg/
http-core/issues/966>)
* In Section 7.1.2, improve readability of formerly overlong
sentence (<https://github.com/httpwg/http-core/issues/966>)
* Slightly rephrase Section 9.8 (<https://github.com/httpwg/http-
core/pull/972>)
Acknowledgements
See Appendix "Acknowledgements" of [HTTP].
Index
A C D F G H M O R T X
A
absolute-form (of request-target) Section 3.2.2
application/http Media Type Section 10.2
asterisk-form (of request-target) Section 3.2.4
authority-form (of request-target) Section 3.2.3
C
Connection header field Section 9.6
Content-Length header field Section 6.2
Content-Transfer-Encoding header field Appendix B.5
chunked (Coding Format) Section 6.1; Section 6.3
chunked (transfer coding) Section 7.1
close Section 9.3; Section 9.6
compress (transfer coding) Section 7.2
D
deflate (transfer coding) Section 7.2
F
Fields
Close Section 9.6, Paragraph 4
MIME-Version Appendix B.1
Transfer-Encoding Section 6.1
G
Grammar
ALPHA Section 1.2
CR Section 1.2
CRLF Section 1.2
CTL Section 1.2
DIGIT Section 1.2
DQUOTE Section 1.2
HEXDIG Section 1.2
HTAB Section 1.2
HTTP-message Section 2.1
HTTP-name Section 2.3
HTTP-version Section 2.3
LF Section 1.2
OCTET Section 1.2
SP Section 1.2
Transfer-Encoding Section 6.1
VCHAR Section 1.2
absolute-form Section 3.2; Section 3.2.2
asterisk-form Section 3.2; Section 3.2.4
authority-form Section 3.2; Section 3.2.3
chunk Section 7.1
chunk-data Section 7.1
chunk-ext Section 7.1; Section 7.1.1
chunk-ext-name Section 7.1.1
chunk-ext-val Section 7.1.1
chunk-size Section 7.1
chunked-body Section 7.1
field-line Section 5; Section 7.1.2
field-name Section 5
field-value Section 5
last-chunk Section 7.1
message-body Section 6
method Section 3.1
obs-fold Section 5.2
origin-form Section 3.2; Section 3.2.1
reason-phrase Section 4
request-line Section 3
request-target Section 3.2
start-line Section 2.1
status-code Section 4
status-line Section 4
trailer-section Section 7.1; Section 7.1.2
gzip (transfer coding) Section 7.2
H
Header Fields
MIME-Version Appendix B.1
Transfer-Encoding Section 6.1
header line Section 2.1
header section Section 2.1
headers Section 2.1
M
MIME-Version header field Appendix B.1
Media Type
application/http Section 10.2
message/http Section 10.1
message/http Media Type Section 10.1
method Section 3.1
O
origin-form (of request-target) Section 3.2.1
R
request-target Section 3.2
T
Transfer-Encoding header field Section 6.1
X
x-compress (transfer coding) Section 7.2
x-gzip (transfer coding) Section 7.2
Authors' Addresses Authors' Addresses
Roy T. Fielding (editor) Roy T. Fielding (editor)
Adobe Systems Incorporated Adobe
345 Park Ave 345 Park Ave
San Jose, CA 95110 San Jose, CA 95110
USA United States of America
EMail: fielding@gbiv.com Email: fielding@gbiv.com
URI: http://roy.gbiv.com/ URI: https://roy.gbiv.com/
Julian F. Reschke (editor) Mark Nottingham (editor)
Fastly
Prahran VIC
Australia
Email: mnot@mnot.net
URI: https://www.mnot.net/
Julian Reschke (editor)
greenbytes GmbH greenbytes GmbH
Hafenweg 16 Hafenweg 16
Muenster, NW 48155 48155 M√ľnster
Germany Germany
EMail: julian.reschke@greenbytes.de Email: julian.reschke@greenbytes.de
URI: http://greenbytes.de/tech/webdav/ URI: https://greenbytes.de/tech/webdav/
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