draft-ietf-httpbis-p2-semantics-16.txt   draft-ietf-httpbis-p2-semantics-17.txt 
HTTPbis Working Group R. Fielding, Ed. HTTPbis Working Group R. Fielding, Ed.
Internet-Draft Adobe Internet-Draft Adobe
Obsoletes: 2616 (if approved) J. Gettys Obsoletes: 2616 (if approved) J. Gettys
Updates: 2817 (if approved) Alcatel-Lucent Updates: 2817 (if approved) Alcatel-Lucent
Intended status: Standards Track J. Mogul Intended status: Standards Track J. Mogul
Expires: February 25, 2012 HP Expires: May 3, 2012 HP
H. Frystyk H. Frystyk
Microsoft Microsoft
L. Masinter L. Masinter
Adobe Adobe
P. Leach P. Leach
Microsoft Microsoft
T. Berners-Lee T. Berners-Lee
W3C/MIT W3C/MIT
Y. Lafon, Ed. Y. Lafon, Ed.
W3C W3C
J. Reschke, Ed. J. Reschke, Ed.
greenbytes greenbytes
August 24, 2011 October 31, 2011
HTTP/1.1, part 2: Message Semantics HTTP/1.1, part 2: Message Semantics
draft-ietf-httpbis-p2-semantics-16 draft-ietf-httpbis-p2-semantics-17
Abstract Abstract
The Hypertext Transfer Protocol (HTTP) is an application-level The Hypertext Transfer Protocol (HTTP) is an application-level
protocol for distributed, collaborative, hypertext information protocol for distributed, collaborative, hypertext information
systems. HTTP has been in use by the World Wide Web global systems. HTTP has been in use by the World Wide Web global
information initiative since 1990. This document is Part 2 of the information initiative since 1990. This document is Part 2 of the
seven-part specification that defines the protocol referred to as seven-part specification that defines the protocol referred to as
"HTTP/1.1" and, taken together, obsoletes RFC 2616. "HTTP/1.1" and, taken together, obsoletes RFC 2616.
skipping to change at page 2, line 5 skipping to change at page 2, line 5
Discussion of this draft should take place on the HTTPBIS working Discussion of this draft should take place on the HTTPBIS working
group mailing list (ietf-http-wg@w3.org), which is archived at group mailing list (ietf-http-wg@w3.org), which is archived at
<http://lists.w3.org/Archives/Public/ietf-http-wg/>. <http://lists.w3.org/Archives/Public/ietf-http-wg/>.
The current issues list is at The current issues list is at
<http://tools.ietf.org/wg/httpbis/trac/report/3> and related <http://tools.ietf.org/wg/httpbis/trac/report/3> and related
documents (including fancy diffs) can be found at documents (including fancy diffs) can be found at
<http://tools.ietf.org/wg/httpbis/>. <http://tools.ietf.org/wg/httpbis/>.
The changes in this draft are summarized in Appendix C.17. The changes in this draft are summarized in Appendix C.18.
Status of This Memo Status of This Memo
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Copyright Notice Copyright Notice
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document authors. All rights reserved. document authors. All rights reserved.
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modifications of such material outside the IETF Standards Process. modifications of such material outside the IETF Standards Process.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . . 6 1.1. Conformance and Error Handling . . . . . . . . . . . . . . 6
1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 6 1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 7
1.2.1. Core Rules . . . . . . . . . . . . . . . . . . . . . . 7 1.2.1. Core Rules . . . . . . . . . . . . . . . . . . . . . . 7
1.2.2. ABNF Rules defined in other Parts of the 1.2.2. ABNF Rules defined in other Parts of the
Specification . . . . . . . . . . . . . . . . . . . . 7 Specification . . . . . . . . . . . . . . . . . . . . 7
2. Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2. Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.1. Overview of Methods . . . . . . . . . . . . . . . . . . . 8 2.1. Overview of Methods . . . . . . . . . . . . . . . . . . . 8
2.2. Method Registry . . . . . . . . . . . . . . . . . . . . . 8 2.2. Method Registry . . . . . . . . . . . . . . . . . . . . . 8
2.2.1. Considerations for New Methods . . . . . . . . . . . . 8 2.2.1. Considerations for New Methods . . . . . . . . . . . . 9
3. Request Header Fields . . . . . . . . . . . . . . . . . . . . 9 3. Header Fields . . . . . . . . . . . . . . . . . . . . . . . . 9
4. Status Code and Reason Phrase . . . . . . . . . . . . . . . . 10 3.1. Considerations for Creating Header Fields . . . . . . . . 9
4.1. Overview of Status Codes . . . . . . . . . . . . . . . . . 10 3.2. Request Header Fields . . . . . . . . . . . . . . . . . . 11
4.2. Status Code Registry . . . . . . . . . . . . . . . . . . . 12 3.3. Response Header Fields . . . . . . . . . . . . . . . . . . 12
4.2.1. Considerations for New Status Codes . . . . . . . . . 12 4. Status Code and Reason Phrase . . . . . . . . . . . . . . . . 12
5. Response Header Fields . . . . . . . . . . . . . . . . . . . . 13 4.1. Overview of Status Codes . . . . . . . . . . . . . . . . . 13
6. Representation . . . . . . . . . . . . . . . . . . . . . . . . 13 4.2. Status Code Registry . . . . . . . . . . . . . . . . . . . 15
6.1. Identifying the Resource Associated with a 4.2.1. Considerations for New Status Codes . . . . . . . . . 15
Representation . . . . . . . . . . . . . . . . . . . . . . 13 5. Representation . . . . . . . . . . . . . . . . . . . . . . . . 16
7. Method Definitions . . . . . . . . . . . . . . . . . . . . . . 14 5.1. Identifying the Resource Associated with a
7.1. Safe and Idempotent Methods . . . . . . . . . . . . . . . 14 Representation . . . . . . . . . . . . . . . . . . . . . . 16
7.1.1. Safe Methods . . . . . . . . . . . . . . . . . . . . . 14 6. Method Definitions . . . . . . . . . . . . . . . . . . . . . . 17
7.1.2. Idempotent Methods . . . . . . . . . . . . . . . . . . 15 6.1. Safe and Idempotent Methods . . . . . . . . . . . . . . . 17
7.2. OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . 15 6.1.1. Safe Methods . . . . . . . . . . . . . . . . . . . . . 17
7.3. GET . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 6.1.2. Idempotent Methods . . . . . . . . . . . . . . . . . . 17
7.4. HEAD . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.2. OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . 18
7.5. POST . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 6.3. GET . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.6. PUT . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6.4. HEAD . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.7. DELETE . . . . . . . . . . . . . . . . . . . . . . . . . . 20 6.5. POST . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
7.8. TRACE . . . . . . . . . . . . . . . . . . . . . . . . . . 21 6.6. PUT . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.9. CONNECT . . . . . . . . . . . . . . . . . . . . . . . . . 21 6.7. DELETE . . . . . . . . . . . . . . . . . . . . . . . . . . 23
7.9.1. Establishing a Tunnel with CONNECT . . . . . . . . . . 22 6.8. TRACE . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8. Status Code Definitions . . . . . . . . . . . . . . . . . . . 23 6.9. CONNECT . . . . . . . . . . . . . . . . . . . . . . . . . 24
8.1. Informational 1xx . . . . . . . . . . . . . . . . . . . . 23 6.9.1. Establishing a Tunnel with CONNECT . . . . . . . . . . 25
8.1.1. 100 Continue . . . . . . . . . . . . . . . . . . . . . 23 7. Status Code Definitions . . . . . . . . . . . . . . . . . . . 25
8.1.2. 101 Switching Protocols . . . . . . . . . . . . . . . 23 7.1. Informational 1xx . . . . . . . . . . . . . . . . . . . . 26
8.2. Successful 2xx . . . . . . . . . . . . . . . . . . . . . . 24 7.1.1. 100 Continue . . . . . . . . . . . . . . . . . . . . . 26
8.2.1. 200 OK . . . . . . . . . . . . . . . . . . . . . . . . 24 7.1.2. 101 Switching Protocols . . . . . . . . . . . . . . . 26
8.2.2. 201 Created . . . . . . . . . . . . . . . . . . . . . 24 7.2. Successful 2xx . . . . . . . . . . . . . . . . . . . . . . 27
8.2.3. 202 Accepted . . . . . . . . . . . . . . . . . . . . . 25 7.2.1. 200 OK . . . . . . . . . . . . . . . . . . . . . . . . 27
8.2.4. 203 Non-Authoritative Information . . . . . . . . . . 25 7.2.2. 201 Created . . . . . . . . . . . . . . . . . . . . . 27
8.2.5. 204 No Content . . . . . . . . . . . . . . . . . . . . 25 7.2.3. 202 Accepted . . . . . . . . . . . . . . . . . . . . . 28
8.2.6. 205 Reset Content . . . . . . . . . . . . . . . . . . 26 7.2.4. 203 Non-Authoritative Information . . . . . . . . . . 28
8.2.7. 206 Partial Content . . . . . . . . . . . . . . . . . 26 7.2.5. 204 No Content . . . . . . . . . . . . . . . . . . . . 28
8.3. Redirection 3xx . . . . . . . . . . . . . . . . . . . . . 26 7.2.6. 205 Reset Content . . . . . . . . . . . . . . . . . . 29
8.3.1. 300 Multiple Choices . . . . . . . . . . . . . . . . . 27 7.2.7. 206 Partial Content . . . . . . . . . . . . . . . . . 29
8.3.2. 301 Moved Permanently . . . . . . . . . . . . . . . . 27 7.3. Redirection 3xx . . . . . . . . . . . . . . . . . . . . . 29
8.3.3. 302 Found . . . . . . . . . . . . . . . . . . . . . . 28 7.3.1. 300 Multiple Choices . . . . . . . . . . . . . . . . . 30
8.3.4. 303 See Other . . . . . . . . . . . . . . . . . . . . 28 7.3.2. 301 Moved Permanently . . . . . . . . . . . . . . . . 31
8.3.5. 304 Not Modified . . . . . . . . . . . . . . . . . . . 29 7.3.3. 302 Found . . . . . . . . . . . . . . . . . . . . . . 32
8.3.6. 305 Use Proxy . . . . . . . . . . . . . . . . . . . . 29 7.3.4. 303 See Other . . . . . . . . . . . . . . . . . . . . 32
8.3.7. 306 (Unused) . . . . . . . . . . . . . . . . . . . . . 29 7.3.5. 304 Not Modified . . . . . . . . . . . . . . . . . . . 33
8.3.8. 307 Temporary Redirect . . . . . . . . . . . . . . . . 29 7.3.6. 305 Use Proxy . . . . . . . . . . . . . . . . . . . . 33
8.4. Client Error 4xx . . . . . . . . . . . . . . . . . . . . . 30 7.3.7. 306 (Unused) . . . . . . . . . . . . . . . . . . . . . 33
8.4.1. 400 Bad Request . . . . . . . . . . . . . . . . . . . 30 7.3.8. 307 Temporary Redirect . . . . . . . . . . . . . . . . 33
8.4.2. 401 Unauthorized . . . . . . . . . . . . . . . . . . . 30 7.4. Client Error 4xx . . . . . . . . . . . . . . . . . . . . . 34
8.4.3. 402 Payment Required . . . . . . . . . . . . . . . . . 30 7.4.1. 400 Bad Request . . . . . . . . . . . . . . . . . . . 34
8.4.4. 403 Forbidden . . . . . . . . . . . . . . . . . . . . 30 7.4.2. 401 Unauthorized . . . . . . . . . . . . . . . . . . . 34
8.4.5. 404 Not Found . . . . . . . . . . . . . . . . . . . . 31 7.4.3. 402 Payment Required . . . . . . . . . . . . . . . . . 34
8.4.6. 405 Method Not Allowed . . . . . . . . . . . . . . . . 31 7.4.4. 403 Forbidden . . . . . . . . . . . . . . . . . . . . 34
8.4.7. 406 Not Acceptable . . . . . . . . . . . . . . . . . . 31 7.4.5. 404 Not Found . . . . . . . . . . . . . . . . . . . . 35
8.4.8. 407 Proxy Authentication Required . . . . . . . . . . 32 7.4.6. 405 Method Not Allowed . . . . . . . . . . . . . . . . 35
8.4.9. 408 Request Timeout . . . . . . . . . . . . . . . . . 32 7.4.7. 406 Not Acceptable . . . . . . . . . . . . . . . . . . 35
8.4.10. 409 Conflict . . . . . . . . . . . . . . . . . . . . . 32 7.4.8. 407 Proxy Authentication Required . . . . . . . . . . 35
8.4.11. 410 Gone . . . . . . . . . . . . . . . . . . . . . . . 32 7.4.9. 408 Request Timeout . . . . . . . . . . . . . . . . . 36
8.4.12. 411 Length Required . . . . . . . . . . . . . . . . . 33 7.4.10. 409 Conflict . . . . . . . . . . . . . . . . . . . . . 36
8.4.13. 412 Precondition Failed . . . . . . . . . . . . . . . 33 7.4.11. 410 Gone . . . . . . . . . . . . . . . . . . . . . . . 36
8.4.14. 413 Request Representation Too Large . . . . . . . . . 33 7.4.12. 411 Length Required . . . . . . . . . . . . . . . . . 37
8.4.15. 414 URI Too Long . . . . . . . . . . . . . . . . . . . 33 7.4.13. 412 Precondition Failed . . . . . . . . . . . . . . . 37
8.4.16. 415 Unsupported Media Type . . . . . . . . . . . . . . 34 7.4.14. 413 Request Representation Too Large . . . . . . . . . 37
8.4.17. 416 Requested Range Not Satisfiable . . . . . . . . . 34 7.4.15. 414 URI Too Long . . . . . . . . . . . . . . . . . . . 37
8.4.18. 417 Expectation Failed . . . . . . . . . . . . . . . . 34 7.4.16. 415 Unsupported Media Type . . . . . . . . . . . . . . 37
8.4.19. 426 Upgrade Required . . . . . . . . . . . . . . . . . 34 7.4.17. 416 Requested Range Not Satisfiable . . . . . . . . . 38
8.5. Server Error 5xx . . . . . . . . . . . . . . . . . . . . . 34 7.4.18. 417 Expectation Failed . . . . . . . . . . . . . . . . 38
8.5.1. 500 Internal Server Error . . . . . . . . . . . . . . 35 7.4.19. 426 Upgrade Required . . . . . . . . . . . . . . . . . 38
8.5.2. 501 Not Implemented . . . . . . . . . . . . . . . . . 35 7.5. Server Error 5xx . . . . . . . . . . . . . . . . . . . . . 38
8.5.3. 502 Bad Gateway . . . . . . . . . . . . . . . . . . . 35 7.5.1. 500 Internal Server Error . . . . . . . . . . . . . . 38
8.5.4. 503 Service Unavailable . . . . . . . . . . . . . . . 35 7.5.2. 501 Not Implemented . . . . . . . . . . . . . . . . . 39
8.5.5. 504 Gateway Timeout . . . . . . . . . . . . . . . . . 35 7.5.3. 502 Bad Gateway . . . . . . . . . . . . . . . . . . . 39
8.5.6. 505 HTTP Version Not Supported . . . . . . . . . . . . 36 7.5.4. 503 Service Unavailable . . . . . . . . . . . . . . . 39
9. Header Field Definitions . . . . . . . . . . . . . . . . . . . 36 7.5.5. 504 Gateway Timeout . . . . . . . . . . . . . . . . . 39
9.1. Allow . . . . . . . . . . . . . . . . . . . . . . . . . . 36 7.5.6. 505 HTTP Version Not Supported . . . . . . . . . . . . 39
9.2. Expect . . . . . . . . . . . . . . . . . . . . . . . . . . 36 8. Date/Time Formats . . . . . . . . . . . . . . . . . . . . . . 40
9.3. From . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 9. Header Field Definitions . . . . . . . . . . . . . . . . . . . 42
9.4. Location . . . . . . . . . . . . . . . . . . . . . . . . . 38 9.1. Allow . . . . . . . . . . . . . . . . . . . . . . . . . . 42
9.5. Max-Forwards . . . . . . . . . . . . . . . . . . . . . . . 39 9.2. Date . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
9.6. Referer . . . . . . . . . . . . . . . . . . . . . . . . . 39 9.3. Expect . . . . . . . . . . . . . . . . . . . . . . . . . . 44
9.7. Retry-After . . . . . . . . . . . . . . . . . . . . . . . 40 9.4. From . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
9.8. Server . . . . . . . . . . . . . . . . . . . . . . . . . . 40 9.5. Location . . . . . . . . . . . . . . . . . . . . . . . . . 45
9.9. User-Agent . . . . . . . . . . . . . . . . . . . . . . . . 41 9.6. Max-Forwards . . . . . . . . . . . . . . . . . . . . . . . 46
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42 9.7. Referer . . . . . . . . . . . . . . . . . . . . . . . . . 47
10.1. Method Registry . . . . . . . . . . . . . . . . . . . . . 42 9.8. Retry-After . . . . . . . . . . . . . . . . . . . . . . . 47
10.2. Status Code Registry . . . . . . . . . . . . . . . . . . . 42 9.9. Server . . . . . . . . . . . . . . . . . . . . . . . . . . 48
10.3. Header Field Registration . . . . . . . . . . . . . . . . 43 9.10. User-Agent . . . . . . . . . . . . . . . . . . . . . . . . 48
11. Security Considerations . . . . . . . . . . . . . . . . . . . 44 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 49
11.1. Transfer of Sensitive Information . . . . . . . . . . . . 44 10.1. Method Registry . . . . . . . . . . . . . . . . . . . . . 49
11.2. Encoding Sensitive Information in URIs . . . . . . . . . . 45 10.2. Status Code Registry . . . . . . . . . . . . . . . . . . . 49
11.3. Location Headers and Spoofing . . . . . . . . . . . . . . 46 10.3. Header Field Registration . . . . . . . . . . . . . . . . 51
11.4. Security Considerations for CONNECT . . . . . . . . . . . 46 11. Security Considerations . . . . . . . . . . . . . . . . . . . 51
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 46 11.1. Transfer of Sensitive Information . . . . . . . . . . . . 51
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 46 11.2. Encoding Sensitive Information in URIs . . . . . . . . . . 52
13.1. Normative References . . . . . . . . . . . . . . . . . . . 46 11.3. Location Headers and Spoofing . . . . . . . . . . . . . . 53
13.2. Informative References . . . . . . . . . . . . . . . . . . 47 11.4. Security Considerations for CONNECT . . . . . . . . . . . 53
Appendix A. Changes from RFC 2616 . . . . . . . . . . . . . . . . 48 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 53
Appendix B. Collected ABNF . . . . . . . . . . . . . . . . . . . 49 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 53
13.1. Normative References . . . . . . . . . . . . . . . . . . . 53
13.2. Informative References . . . . . . . . . . . . . . . . . . 54
Appendix A. Changes from RFC 2616 . . . . . . . . . . . . . . . . 55
Appendix B. Collected ABNF . . . . . . . . . . . . . . . . . . . 56
Appendix C. Change Log (to be removed by RFC Editor before Appendix C. Change Log (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 51 publication) . . . . . . . . . . . . . . . . . . . . 59
C.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . . 51 C.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . . 59
C.2. Since draft-ietf-httpbis-p2-semantics-00 . . . . . . . . . 51 C.2. Since draft-ietf-httpbis-p2-semantics-00 . . . . . . . . . 59
C.3. Since draft-ietf-httpbis-p2-semantics-01 . . . . . . . . . 52 C.3. Since draft-ietf-httpbis-p2-semantics-01 . . . . . . . . . 59
C.4. Since draft-ietf-httpbis-p2-semantics-02 . . . . . . . . . 52 C.4. Since draft-ietf-httpbis-p2-semantics-02 . . . . . . . . . 60
C.5. Since draft-ietf-httpbis-p2-semantics-03 . . . . . . . . . 53 C.5. Since draft-ietf-httpbis-p2-semantics-03 . . . . . . . . . 61
C.6. Since draft-ietf-httpbis-p2-semantics-04 . . . . . . . . . 53 C.6. Since draft-ietf-httpbis-p2-semantics-04 . . . . . . . . . 61
C.7. Since draft-ietf-httpbis-p2-semantics-05 . . . . . . . . . 54 C.7. Since draft-ietf-httpbis-p2-semantics-05 . . . . . . . . . 61
C.8. Since draft-ietf-httpbis-p2-semantics-06 . . . . . . . . . 54 C.8. Since draft-ietf-httpbis-p2-semantics-06 . . . . . . . . . 62
C.9. Since draft-ietf-httpbis-p2-semantics-07 . . . . . . . . . 54 C.9. Since draft-ietf-httpbis-p2-semantics-07 . . . . . . . . . 62
C.10. Since draft-ietf-httpbis-p2-semantics-08 . . . . . . . . . 55 C.10. Since draft-ietf-httpbis-p2-semantics-08 . . . . . . . . . 63
C.11. Since draft-ietf-httpbis-p2-semantics-09 . . . . . . . . . 55 C.11. Since draft-ietf-httpbis-p2-semantics-09 . . . . . . . . . 63
C.12. Since draft-ietf-httpbis-p2-semantics-10 . . . . . . . . . 55 C.12. Since draft-ietf-httpbis-p2-semantics-10 . . . . . . . . . 63
C.13. Since draft-ietf-httpbis-p2-semantics-11 . . . . . . . . . 56 C.13. Since draft-ietf-httpbis-p2-semantics-11 . . . . . . . . . 64
C.14. Since draft-ietf-httpbis-p2-semantics-12 . . . . . . . . . 56 C.14. Since draft-ietf-httpbis-p2-semantics-12 . . . . . . . . . 64
C.15. Since draft-ietf-httpbis-p2-semantics-13 . . . . . . . . . 58 C.15. Since draft-ietf-httpbis-p2-semantics-13 . . . . . . . . . 65
C.16. Since draft-ietf-httpbis-p2-semantics-14 . . . . . . . . . 58 C.16. Since draft-ietf-httpbis-p2-semantics-14 . . . . . . . . . 66
C.17. Since draft-ietf-httpbis-p2-semantics-15 . . . . . . . . . 58 C.17. Since draft-ietf-httpbis-p2-semantics-15 . . . . . . . . . 66
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 C.18. Since draft-ietf-httpbis-p2-semantics-16 . . . . . . . . . 66
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
1. Introduction 1. Introduction
This document defines HTTP/1.1 request and response semantics. Each This document defines HTTP/1.1 request and response semantics. Each
HTTP message, as defined in [Part1], is in the form of either a HTTP message, as defined in [Part1], is in the form of either a
request or a response. An HTTP server listens on a connection for request or a response. An HTTP server listens on a connection for
HTTP requests and responds to each request, in the order received on HTTP requests and responds to each request, in the order received on
that connection, with one or more HTTP response messages. This that connection, with one or more HTTP response messages. This
document defines the commonly agreed upon semantics of the HTTP document defines the commonly agreed upon semantics of the HTTP
uniform interface, the intentions defined by each request method, and uniform interface, the intentions defined by each request method, and
skipping to change at page 6, line 27 skipping to change at page 6, line 27
This document is currently disorganized in order to minimize the This document is currently disorganized in order to minimize the
changes between drafts and enable reviewers to see the smaller errata changes between drafts and enable reviewers to see the smaller errata
changes. A future draft will reorganize the sections to better changes. A future draft will reorganize the sections to better
reflect the content. In particular, the sections will be ordered reflect the content. In particular, the sections will be ordered
according to the typical processing of an HTTP request message (after according to the typical processing of an HTTP request message (after
message parsing): resource mapping, methods, request modifying header message parsing): resource mapping, methods, request modifying header
fields, response status, status modifying header fields, and resource fields, response status, status modifying header fields, and resource
metadata. The current mess reflects how widely dispersed these metadata. The current mess reflects how widely dispersed these
topics and associated requirements had become in [RFC2616]. topics and associated requirements had become in [RFC2616].
1.1. Requirements 1.1. Conformance and Error Handling
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", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
An implementation is not compliant if it fails to satisfy one or more This document defines conformance criteria for several roles in HTTP
of the "MUST" or "REQUIRED" level requirements for the protocols it communication, including Senders, Recipients, Clients, Servers, User-
implements. An implementation that satisfies all the "MUST" or Agents, Origin Servers, Intermediaries, Proxies and Gateways. See
"REQUIRED" level and all the "SHOULD" level requirements for its Section 2 of [Part1] for definitions of these terms.
protocols is said to be "unconditionally compliant"; one that
satisfies all the "MUST" level requirements but not all the "SHOULD" An implementation is considered conformant if it complies with all of
level requirements for its protocols is said to be "conditionally the requirements associated with its role(s). Note that SHOULD-level
compliant". requirements are relevant here, unless one of the documented
exceptions is applicable.
This document also uses ABNF to define valid protocol elements
(Section 1.2). In addition to the prose requirements placed upon
them, Senders MUST NOT generate protocol elements that are invalid.
Unless noted otherwise, Recipients MAY take steps to recover a usable
protocol element from an invalid construct. However, HTTP does not
define specific error handling mechanisms, except in cases where it
has direct impact on security. This is because different uses of the
protocol require different error handling strategies; for example, a
Web browser may wish to transparently recover from a response where
the Location header field doesn't parse according to the ABNF,
whereby in a systems control protocol using HTTP, this type of error
recovery could lead to dangerous consequences.
1.2. Syntax Notation 1.2. Syntax Notation
This specification uses the ABNF syntax defined in Section 1.2 of This specification uses the ABNF syntax defined in Section 1.2 of
[Part1] (which extends the syntax defined in [RFC5234] with a list [Part1] (which extends the syntax defined in [RFC5234] with a list
rule). Appendix B shows the collected ABNF, with the list rule rule). Appendix B shows the collected ABNF, with the list rule
expanded. expanded.
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), LF (line feed), OCTET (any 8-bit HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line
sequence of data), SP (space), VCHAR (any visible USASCII character), feed), OCTET (any 8-bit sequence of data), SP (space), and VCHAR (any
and WSP (whitespace). visible US-ASCII character).
1.2.1. Core Rules 1.2.1. Core Rules
The core rules below are defined in [Part1]: The core rules below are defined in [Part1]:
OWS = <OWS, defined in [Part1], Section 1.2.2> OWS = <OWS, defined in [Part1], Section 1.2.2>
RWS = <RWS, defined in [Part1], Section 1.2.2> RWS = <RWS, defined in [Part1], Section 1.2.2>
obs-text = <obs-text, defined in [Part1], Section 1.2.2> obs-text = <obs-text, defined in [Part1], Section 1.2.2>
quoted-string = <quoted-string, defined in [Part1], Section 3.2.3> quoted-string = <quoted-string, defined in [Part1], Section 3.2.3>
token = <token, defined in [Part1], Section 3.2.3> token = <token, defined in [Part1], Section 3.2.3>
1.2.2. ABNF Rules defined in other Parts of the Specification 1.2.2. ABNF Rules defined in other Parts of the Specification
The ABNF rules below are defined in other parts: The ABNF rules below are defined in other parts:
absolute-URI = <absolute-URI, defined in [Part1], Section 2.7> absolute-URI = <absolute-URI, defined in [Part1], Section 2.7>
comment = <comment, defined in [Part1], Section 3.2> comment = <comment, defined in [Part1], Section 3.2>
HTTP-date = <HTTP-date, defined in [Part1], Section 6.1>
partial-URI = <partial-URI, defined in [Part1], Section 2.7> partial-URI = <partial-URI, defined in [Part1], Section 2.7>
product = <product, defined in [Part1], Section 6.3> product = <product, defined in [Part1], Section 5.2>
URI-reference = <URI-reference, defined in [Part1], Section 2.7> URI-reference = <URI-reference, defined in [Part1], Section 2.7>
2. Method 2. 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 (Section 4.3 of [Part1]). The method is case- target resource (Section 4.3 of [Part1]). The method is case-
sensitive. sensitive.
Method = token Method = token
skipping to change at page 7, line 47 skipping to change at page 8, line 13
Allow header field (Section 9.1). The status code of the response Allow header field (Section 9.1). The status code of the response
always notifies the client whether a method is currently allowed on a always notifies the client whether a method is currently allowed on a
resource, since the set of allowed methods can change dynamically. resource, since the set of allowed methods can change dynamically.
An origin server SHOULD respond with the status code 405 (Method Not An origin server SHOULD respond with the status code 405 (Method Not
Allowed) if the method is known by the origin server but not allowed Allowed) if the method is known by the origin server but not allowed
for the resource, and 501 (Not Implemented) if the method is for the resource, and 501 (Not Implemented) if the method is
unrecognized or not implemented by the origin server. The methods unrecognized or not implemented by the origin server. The methods
GET and HEAD MUST be supported by all general-purpose servers. All GET and HEAD MUST be supported by all general-purpose servers. All
other methods are OPTIONAL; however, if the above methods are other methods are OPTIONAL; however, if the above methods are
implemented, they MUST be implemented with the same semantics as implemented, they MUST be implemented with the same semantics as
those specified in Section 7. those specified in Section 6.
2.1. Overview of Methods 2.1. Overview of Methods
The methods listed below are defined in Section 7. The methods listed below are defined in Section 6.
+-------------+---------------+ +-------------+---------------+
| Method Name | Defined in... | | Method Name | Defined in... |
+-------------+---------------+ +-------------+---------------+
| OPTIONS | Section 7.2 | | OPTIONS | Section 6.2 |
| GET | Section 7.3 | | GET | Section 6.3 |
| HEAD | Section 7.4 | | HEAD | Section 6.4 |
| POST | Section 7.5 | | POST | Section 6.5 |
| PUT | Section 7.6 | | PUT | Section 6.6 |
| DELETE | Section 7.7 | | DELETE | Section 6.7 |
| TRACE | Section 7.8 | | TRACE | Section 6.8 |
| CONNECT | Section 7.9 | | CONNECT | Section 6.9 |
+-------------+---------------+ +-------------+---------------+
Note that this list is not exhaustive -- it does not include request Note that this list is not exhaustive -- it does not include request
methods defined in other specifications. methods defined in other specifications.
2.2. Method Registry 2.2. Method Registry
The HTTP Method Registry defines the name space for the Method token The HTTP Method Registry defines the name space for the Method token
in the Request line of an HTTP request. in the Request line of an HTTP request.
Registrations MUST include the following fields: Registrations MUST include the following fields:
o Method Name (see Section 2) o Method Name (see Section 2)
o Safe ("yes" or "no", see Section 7.1.1) o Safe ("yes" or "no", see Section 6.1.1)
o Pointer to specification text o Pointer to specification text
Values to be added to this name space are subject to IETF review Values to be added to this name space are subject to IETF review
([RFC5226], Section 4.1). ([RFC5226], Section 4.1).
The registry itself is maintained at The registry itself is maintained at
<http://www.iana.org/assignments/http-methods>. <http://www.iana.org/assignments/http-methods>.
2.2.1. Considerations for New Methods 2.2.1. Considerations for New Methods
skipping to change at page 9, line 16 skipping to change at page 9, line 27
so that this is clear. so that this is clear.
Due to the parsing rules defined in Section 3.3 of [Part1], Due to the parsing rules defined in Section 3.3 of [Part1],
definitions of HTTP methods cannot prohibit the presence of a definitions of HTTP methods cannot prohibit the presence of a
message-body on either the request or the response message (with message-body on either the request or the response message (with
responses to HEAD requests being the single exception). Definitions responses to HEAD requests being the single exception). Definitions
of new methods cannot change this rule, but they can specify that of new methods cannot change this rule, but they can specify that
only zero-length bodies (as opposed to absent bodies) are allowed. only zero-length bodies (as opposed to absent bodies) are allowed.
New method definitions need to indicate whether they are safe New method definitions need to indicate whether they are safe
(Section 7.1.1), what semantics (if any) the request body has, and (Section 6.1.1), what semantics (if any) the request body has, and
whether they are idempotent (Section 7.1.2). They also need to state whether they are idempotent (Section 6.1.2). They also need to state
whether they can be cached ([Part6]); in particular what conditions a whether they can be cached ([Part6]); in particular what conditions a
cache may store the response, and under what conditions such a stored cache may store the response, and under what conditions such a stored
response may be used to satisfy a subsequent request. response may be used to satisfy a subsequent request.
3. Request Header Fields 3. Header Fields
Header fields are key value pairs that can be used to communicate
data about the message, its payload, the target resource, or about
the connection itself (i.e., control data). See Section 3.2 of
[Part1] for a general definition of their syntax.
3.1. Considerations for Creating Header Fields
New header fields are registered using the procedures described in
[RFC3864].
The requirements for header field names are defined in Section 4.1 of
[RFC3864]. Authors of specifications defining new fields are advised
to keep the name as short as practical, and not to prefix them with
"X-" if they are to be registered (either immediately or in the
future).
New header field values typically have their syntax defined using
ABNF ([RFC5234]), using the extensions defined in Section 1.2.1 of
[Part1] as necessary, and are usually constrained to the range of
ASCII characters. Header fields needing a greater range of
characters can use an encoding such as the one defined in [RFC5987].
Because commas (",") are used as a generic delimiter between field-
values, they need to be treated with care if they are allowed in the
field-value's payload. Typically, components that might contain a
comma are protected with double-quotes using the quoted-string ABNF
production (Section 3.2.3 of [Part1]).
For example, a textual date and a URI (either of which might contain
a comma) could be safely carried in field-values like these:
Example-URI-Field: "http://example.com/a.html,foo",
"http://without-a-comma.example.com/"
Example-Date-Field: "Sat, 04 May 1996", "Wed, 14 Sep 2005"
Many header fields use a format including (case-insensitively) named
parameters (for instance, Content-Type, defined in Section 6.8 of
[Part3]). Allowing both unquoted (token) and quoted (quoted-string)
syntax for the parameter value enables recipients to use existing
parser components. When allowing both forms, the meaning of a
parameter value ought to be independent of the syntax used for it
(for an example, see the notes on parameter handling for media types
in Section 2.3 of [Part3]).
Authors of specifications defining new header fields are advised to
consider documenting:
o Whether the field is a single value, or whether it can be a list
(delimited by commas; see Section 3.2 of [Part1]).
If it does not use the list syntax, document how to treat messages
where the header field occurs multiple times (a sensible default
would be to ignore the header field, but this might not always be
the right choice).
Note that intermediaries and software libraries might combine
multiple header field instances into a single one, despite the
header field not allowing this. A robust format enables
recipients to discover these situations (good example: "Content-
Type", as the comma can only appear inside quoted strings; bad
example: "Location", as a comma can occur inside a URI).
o Under what conditions the header field can be used; e.g., only in
responses or requests, in all messages, only on responses to a
particular request method.
o Whether it is appropriate to list the field-name in the Connection
header (i.e., if the header is to be hop-by-hop, see Section 8.1
of [Part1]).
o Under what conditions intermediaries are allowed to modify the
header field's value, insert or delete it.
o How the header might interact with caching (see [Part6]).
o Whether the header field is useful or allowable in trailers (see
Section 5.1.1 of [Part1]).
o Whether the header field should be preserved across redirects.
3.2. Request Header Fields
The request header fields allow the client to pass additional The request header fields allow the client to pass additional
information about the request, and about the client itself, to the information about the request, and about the client itself, to the
server. These fields act as request modifiers, with semantics server. These fields act as request modifiers, with semantics
equivalent to the parameters on a programming language method equivalent to the parameters on a programming language method
invocation. invocation.
+---------------------+------------------------+ +---------------------+------------------------+
| Header Field Name | Defined in... | | Header Field Name | Defined in... |
+---------------------+------------------------+ +---------------------+------------------------+
| Accept | Section 6.1 of [Part3] | | Accept | Section 6.1 of [Part3] |
| Accept-Charset | Section 6.2 of [Part3] | | Accept-Charset | Section 6.2 of [Part3] |
| Accept-Encoding | Section 6.3 of [Part3] | | Accept-Encoding | Section 6.3 of [Part3] |
| Accept-Language | Section 6.4 of [Part3] | | Accept-Language | Section 6.4 of [Part3] |
| Authorization | Section 4.1 of [Part7] | | Authorization | Section 4.1 of [Part7] |
| Expect | Section 9.2 | | Expect | Section 9.3 |
| From | Section 9.3 | | From | Section 9.4 |
| Host | Section 9.4 of [Part1] | | Host | Section 8.3 of [Part1] |
| If-Match | Section 3.1 of [Part4] | | If-Match | Section 3.1 of [Part4] |
| If-Modified-Since | Section 3.3 of [Part4] | | If-Modified-Since | Section 3.3 of [Part4] |
| If-None-Match | Section 3.2 of [Part4] | | If-None-Match | Section 3.2 of [Part4] |
| If-Range | Section 5.3 of [Part5] | | If-Range | Section 5.3 of [Part5] |
| If-Unmodified-Since | Section 3.4 of [Part4] | | If-Unmodified-Since | Section 3.4 of [Part4] |
| Max-Forwards | Section 9.5 | | Max-Forwards | Section 9.6 |
| Proxy-Authorization | Section 4.3 of [Part7] | | Proxy-Authorization | Section 4.3 of [Part7] |
| Range | Section 5.4 of [Part5] | | Range | Section 5.4 of [Part5] |
| Referer | Section 9.6 | | Referer | Section 9.7 |
| TE | Section 9.5 of [Part1] | | TE | Section 8.4 of [Part1] |
| User-Agent | Section 9.9 | | User-Agent | Section 9.10 |
+---------------------+------------------------+ +---------------------+------------------------+
3.3. Response Header Fields
The response header fields allow the server to pass additional
information about the response which cannot be placed in the Status-
Line. These header fields give information about the server and
about further access to the target resource (Section 4.3 of [Part1]).
+--------------------+------------------------+
| Header Field Name | Defined in... |
+--------------------+------------------------+
| Accept-Ranges | Section 5.1 of [Part5] |
| Age | Section 3.1 of [Part6] |
| Allow | Section 9.1 |
| Date | Section 9.2 |
| ETag | Section 2.3 of [Part4] |
| Location | Section 9.5 |
| Proxy-Authenticate | Section 4.2 of [Part7] |
| Retry-After | Section 9.8 |
| Server | Section 9.9 |
| Vary | Section 3.5 of [Part6] |
| WWW-Authenticate | Section 4.4 of [Part7] |
+--------------------+------------------------+
4. Status Code and Reason Phrase 4. Status Code and Reason Phrase
The Status-Code element is a 3-digit integer result code of the The Status-Code element is a 3-digit integer result code of the
attempt to understand and satisfy the request. attempt to understand and satisfy the request.
The Reason-Phrase is intended to give a short textual description of The Reason-Phrase is intended to give a short textual description of
the Status-Code and is intended for a human user. The client does the Status-Code and is intended for a human user. The client does
not need to examine or display the Reason-Phrase. not need to examine or display the Reason-Phrase.
Status-Code = 3DIGIT Status-Code = 3DIGIT
Reason-Phrase = *( WSP / VCHAR / obs-text ) Reason-Phrase = *( HTAB / SP / VCHAR / obs-text )
HTTP status codes are extensible. HTTP applications are not required HTTP status codes are extensible. HTTP applications are not required
to understand the meaning of all registered status codes, though such to understand the meaning of all registered status codes, though such
understanding is obviously desirable. However, applications MUST understanding is obviously desirable. However, applications MUST
understand the class of any status code, as indicated by the first understand the class of any status code, as indicated by the first
digit, and treat any unrecognized response as being equivalent to the digit, and treat any unrecognized response as being equivalent to the
x00 status code of that class, with the exception that an x00 status code of that class, with the exception that an
unrecognized response MUST NOT be cached. For example, if an unrecognized response MUST NOT be cached. For example, if an
unrecognized status code of 431 is received by the client, it can unrecognized status code of 431 is received by the client, it can
safely assume that there was something wrong with its request and safely assume that there was something wrong with its request and
treat the response as if it had received a 400 status code. In such treat the response as if it had received a 400 status code. In such
cases, user agents SHOULD present to the user the representation cases, user agents SHOULD present to the user the representation
enclosed with the response, since that representation is likely to enclosed with the response, since that representation is likely to
include human-readable information which will explain the unusual include human-readable information which will explain the unusual
status. status.
4.1. Overview of Status Codes 4.1. Overview of Status Codes
The status codes listed below are defined in Section 8 of this The status codes listed below are defined in Section 7 of this
specification, Section 4 of [Part4], Section 3 of [Part5], and specification, Section 4 of [Part4], Section 3 of [Part5], and
Section 3 of [Part7]. The reason phrases listed here are only Section 3 of [Part7]. The reason phrases listed here are only
recommendations -- they can be replaced by local equivalents without recommendations -- they can be replaced by local equivalents without
affecting the protocol. affecting the protocol.
+-------------+------------------------------+----------------------+ +-------------+------------------------------+----------------------+
| Status-Code | Reason-Phrase | Defined in... | | Status-Code | Reason-Phrase | Defined in... |
+-------------+------------------------------+----------------------+ +-------------+------------------------------+----------------------+
| 100 | Continue | Section 8.1.1 | | 100 | Continue | Section 7.1.1 |
| 101 | Switching Protocols | Section 8.1.2 | | 101 | Switching Protocols | Section 7.1.2 |
| 200 | OK | Section 8.2.1 | | 200 | OK | Section 7.2.1 |
| 201 | Created | Section 8.2.2 | | 201 | Created | Section 7.2.2 |
| 202 | Accepted | Section 8.2.3 | | 202 | Accepted | Section 7.2.3 |
| 203 | Non-Authoritative | Section 8.2.4 | | 203 | Non-Authoritative | Section 7.2.4 |
| | Information | | | | Information | |
| 204 | No Content | Section 8.2.5 | | 204 | No Content | Section 7.2.5 |
| 205 | Reset Content | Section 8.2.6 | | 205 | Reset Content | Section 7.2.6 |
| 206 | Partial Content | Section 3.1 of | | 206 | Partial Content | Section 3.1 of |
| | | [Part5] | | | | [Part5] |
| 300 | Multiple Choices | Section 8.3.1 | | 300 | Multiple Choices | Section 7.3.1 |
| 301 | Moved Permanently | Section 8.3.2 | | 301 | Moved Permanently | Section 7.3.2 |
| 302 | Found | Section 8.3.3 | | 302 | Found | Section 7.3.3 |
| 303 | See Other | Section 8.3.4 | | 303 | See Other | Section 7.3.4 |
| 304 | Not Modified | Section 4.1 of | | 304 | Not Modified | Section 4.1 of |
| | | [Part4] | | | | [Part4] |
| 305 | Use Proxy | Section 8.3.6 | | 305 | Use Proxy | Section 7.3.6 |
| 307 | Temporary Redirect | Section 8.3.8 | | 307 | Temporary Redirect | Section 7.3.8 |
| 400 | Bad Request | Section 8.4.1 | | 400 | Bad Request | Section 7.4.1 |
| 401 | Unauthorized | Section 3.1 of | | 401 | Unauthorized | Section 3.1 of |
| | | [Part7] | | | | [Part7] |
| 402 | Payment Required | Section 8.4.3 | | 402 | Payment Required | Section 7.4.3 |
| 403 | Forbidden | Section 8.4.4 | | 403 | Forbidden | Section 7.4.4 |
| 404 | Not Found | Section 8.4.5 | | 404 | Not Found | Section 7.4.5 |
| 405 | Method Not Allowed | Section 8.4.6 | | 405 | Method Not Allowed | Section 7.4.6 |
| 406 | Not Acceptable | Section 8.4.7 | | 406 | Not Acceptable | Section 7.4.7 |
| 407 | Proxy Authentication | Section 3.2 of | | 407 | Proxy Authentication | Section 3.2 of |
| | Required | [Part7] | | | Required | [Part7] |
| 408 | Request Time-out | Section 8.4.9 | | 408 | Request Time-out | Section 7.4.9 |
| 409 | Conflict | Section 8.4.10 | | 409 | Conflict | Section 7.4.10 |
| 410 | Gone | Section 8.4.11 | | 410 | Gone | Section 7.4.11 |
| 411 | Length Required | Section 8.4.12 | | 411 | Length Required | Section 7.4.12 |
| 412 | Precondition Failed | Section 4.2 of | | 412 | Precondition Failed | Section 4.2 of |
| | | [Part4] | | | | [Part4] |
| 413 | Request Representation Too | Section 8.4.14 | | 413 | Request Representation Too | Section 7.4.14 |
| | Large | | | | Large | |
| 414 | URI Too Long | Section 8.4.15 | | 414 | URI Too Long | Section 7.4.15 |
| 415 | Unsupported Media Type | Section 8.4.16 | | 415 | Unsupported Media Type | Section 7.4.16 |
| 416 | Requested range not | Section 3.2 of | | 416 | Requested range not | Section 3.2 of |
| | satisfiable | [Part5] | | | satisfiable | [Part5] |
| 417 | Expectation Failed | Section 8.4.18 | | 417 | Expectation Failed | Section 7.4.18 |
| 426 | Upgrade Required | Section 8.4.19 | | 426 | Upgrade Required | Section 7.4.19 |
| 500 | Internal Server Error | Section 8.5.1 | | 500 | Internal Server Error | Section 7.5.1 |
| 501 | Not Implemented | Section 8.5.2 | | 501 | Not Implemented | Section 7.5.2 |
| 502 | Bad Gateway | Section 8.5.3 | | 502 | Bad Gateway | Section 7.5.3 |
| 503 | Service Unavailable | Section 8.5.4 | | 503 | Service Unavailable | Section 7.5.4 |
| 504 | Gateway Time-out | Section 8.5.5 | | 504 | Gateway Time-out | Section 7.5.5 |
| 505 | HTTP Version not supported | Section 8.5.6 | | 505 | HTTP Version not supported | Section 7.5.6 |
+-------------+------------------------------+----------------------+ +-------------+------------------------------+----------------------+
Note that this list is not exhaustive -- it does not include Note that this list is not exhaustive -- it does not include
extension status codes defined in other specifications. extension status codes defined in other specifications.
4.2. Status Code Registry 4.2. Status Code Registry
The HTTP Status Code Registry defines the name space for the Status- The HTTP Status Code Registry defines the name space for the Status-
Code token in the Status-Line of an HTTP response. Code token in the Status-Line of an HTTP response.
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new HTTP status codes be registered in a document that isn't specific new HTTP status codes be registered in a document that isn't specific
to a single application, so that this is clear. to a single application, so that this is clear.
Definitions of new HTTP status codes typically explain the request Definitions of new HTTP status codes typically explain the request
conditions that produce a response containing the status code (e.g., conditions that produce a response containing the status code (e.g.,
combinations of request headers and/or method(s)), along with any combinations of request headers and/or method(s)), along with any
interactions with response headers (e.g., those that are required, interactions with response headers (e.g., those that are required,
those that modify the semantics of the response). those that modify the semantics of the response).
New HTTP status codes are required to fall under one of the New HTTP status codes are required to fall under one of the
categories defined in Section 8. To allow existing parsers to categories defined in Section 7. To allow existing parsers to
properly handle them, new status codes cannot disallow a response properly handle them, new status codes cannot disallow a response
body, although they can mandate a zero-length response body. They body, although they can mandate a zero-length response body. They
can require the presence of one or more particular HTTP response can require the presence of one or more particular HTTP response
header(s). header(s).
Likewise, their definitions can specify that caches are allowed to Likewise, their definitions can specify that caches are allowed to
use heuristics to determine their freshness (see [Part6]; by default, use heuristics to determine their freshness (see [Part6]; by default,
it is not allowed), and can define how to determine the resource it is not allowed), and can define how to determine the resource
which they carry a representation for (see Section 6.1; by default, which they carry a representation for (see Section 5.1; by default,
it is anonymous). it is anonymous).
5. Response Header Fields 5. Representation
The response header fields allow the server to pass additional
information about the response which cannot be placed in the Status-
Line. These header fields give information about the server and
about further access to the target resource (Section 4.3 of [Part1]).
+--------------------+------------------------+
| Header Field Name | Defined in... |
+--------------------+------------------------+
| Accept-Ranges | Section 5.1 of [Part5] |
| Age | Section 3.1 of [Part6] |
| Allow | Section 9.1 |
| ETag | Section 2.3 of [Part4] |
| Location | Section 9.4 |
| Proxy-Authenticate | Section 4.2 of [Part7] |
| Retry-After | Section 9.7 |
| Server | Section 9.8 |
| Vary | Section 3.5 of [Part6] |
| WWW-Authenticate | Section 4.4 of [Part7] |
+--------------------+------------------------+
6. Representation
Request and Response messages MAY transfer a representation if not Request and Response messages MAY transfer a representation if not
otherwise restricted by the request method or response status code. otherwise restricted by the request method or response status code.
A representation consists of metadata (representation header fields) A representation consists of metadata (representation header fields)
and data (representation body). When a complete or partial and data (representation body). When a complete or partial
representation is enclosed in an HTTP message, it is referred to as representation is enclosed in an HTTP message, it is referred to as
the payload of the message. HTTP representations are defined in the payload of the message. HTTP representations are defined in
[Part3]. [Part3].
A representation body is only present in a message when a message- A representation body is only present in a message when a message-
body is present, as described in Section 3.3 of [Part1]. The body is present, as described in Section 3.3 of [Part1]. The
representation body is obtained from the message-body by decoding any representation body is obtained from the message-body by decoding any
Transfer-Encoding that might have been applied to ensure safe and Transfer-Encoding that might have been applied to ensure safe and
proper transfer of the message. proper transfer of the message.
6.1. Identifying the Resource Associated with a Representation 5.1. Identifying the Resource Associated with a Representation
It is sometimes necessary to determine an identifier for the resource It is sometimes necessary to determine an identifier for the resource
associated with a representation. associated with a representation.
An HTTP request representation, when present, is always associated An HTTP request representation, when present, is always associated
with an anonymous (i.e., unidentified) resource. with an anonymous (i.e., unidentified) resource.
In the common case, an HTTP response is a representation of the In the common case, an HTTP response is a representation of the
target resource (see Section 4.3 of [Part1]). However, this is not target resource (see Section 4.3 of [Part1]). However, this is not
always the case. To determine the URI of the resource a response is always the case. To determine the URI of the resource a response is
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assertion cannot be trusted unless it can be verified by other assertion cannot be trusted unless it can be verified by other
means (not defined by HTTP). means (not defined by HTTP).
5. Otherwise, the response is a representation of an anonymous 5. Otherwise, the response is a representation of an anonymous
(i.e., unidentified) resource. (i.e., unidentified) resource.
[[TODO-req-uri: The comparison function is going to have to be [[TODO-req-uri: The comparison function is going to have to be
defined somewhere, because we already need to compare URIs for things defined somewhere, because we already need to compare URIs for things
like cache invalidation.]] like cache invalidation.]]
7. Method Definitions 6. Method Definitions
The set of common request methods for HTTP/1.1 is defined below. The set of common request methods for HTTP/1.1 is defined below.
Although this set can be expanded, additional methods cannot be Although this set can be expanded, additional methods cannot be
assumed to share the same semantics for separately extended clients assumed to share the same semantics for separately extended clients
and servers. and servers.
7.1. Safe and Idempotent Methods 6.1. Safe and Idempotent Methods
7.1.1. Safe Methods 6.1.1. Safe Methods
Implementors need to be aware that the software represents the user Implementors need to be aware that the software represents the user
in their interactions over the Internet, and need to allow the user in their interactions over the Internet, and need to allow the user
to be aware of any actions they take which might have an unexpected to be aware of any actions they take which might have an unexpected
significance to themselves or others. significance to themselves or others.
In particular, the convention has been established that the GET, In particular, the convention has been established that the GET,
HEAD, OPTIONS, and TRACE request methods SHOULD NOT have the HEAD, OPTIONS, and TRACE request methods SHOULD NOT have the
significance of taking an action other than retrieval. These request significance of taking an action other than retrieval. These request
methods ought to be considered "safe". This allows user agents to methods ought to be considered "safe". This allows user agents to
represent other methods, such as POST, PUT and DELETE, in a special represent other methods, such as POST, PUT and DELETE, in a special
way, so that the user is made aware of the fact that a possibly way, so that the user is made aware of the fact that a possibly
unsafe action is being requested. unsafe action is being requested.
Naturally, it is not possible to ensure that the server does not Naturally, it is not possible to ensure that the server does not
generate side-effects as a result of performing a GET request; in generate side-effects as a result of performing a GET request; in
fact, some dynamic resources consider that a feature. The important fact, some dynamic resources consider that a feature. The important
distinction here is that the user did not request the side-effects, distinction here is that the user did not request the side-effects,
so therefore cannot be held accountable for them. so therefore cannot be held accountable for them.
7.1.2. Idempotent Methods 6.1.2. Idempotent Methods
Request methods can also have the property of "idempotence" in that, Request methods can also have the property of "idempotence" in that,
aside from error or expiration issues, the intended effect of aside from error or expiration issues, the intended effect of
multiple identical requests is the same as for a single request. multiple identical requests is the same as for a single request.
PUT, DELETE, and all safe request methods are idempotent. It is PUT, DELETE, and all safe request methods are idempotent. It is
important to note that idempotence refers only to changes requested important to note that idempotence refers only to changes requested
by the client: a server is free to change its state due to multiple by the client: a server is free to change its state due to multiple
requests for the purpose of tracking those requests, versioning of requests for the purpose of tracking those requests, versioning of
results, etc. results, etc.
7.2. OPTIONS 6.2. OPTIONS
The OPTIONS method requests information about the communication The OPTIONS method requests information about the communication
options available on the request/response chain identified by the options available on the request/response chain identified by the
effective request URI. This method allows a client to determine the effective request URI. This method allows a client to determine the
options and/or requirements associated with a resource, or the options and/or requirements associated with a resource, or the
capabilities of a server, without implying a resource action or capabilities of a server, without implying a resource action or
initiating a resource retrieval. initiating a resource retrieval.
Responses to the OPTIONS method are not cacheable. Responses to the OPTIONS method are not cacheable.
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resource (e.g., Allow), possibly including extensions not defined by resource (e.g., Allow), possibly including extensions not defined by
this specification. The response body, if any, SHOULD also include this specification. The response body, if any, SHOULD also include
information about the communication options. The format for such a information about the communication options. The format for such a
body is not defined by this specification, but might be defined by body is not defined by this specification, but might be defined by
future extensions to HTTP. Content negotiation MAY be used to select future extensions to HTTP. Content negotiation MAY be used to select
the appropriate response format. If no response body is included, the appropriate response format. If no response body is included,
the response MUST include a Content-Length field with a field-value the response MUST include a Content-Length field with a field-value
of "0". of "0".
The Max-Forwards header field MAY be used to target a specific proxy The Max-Forwards header field MAY be used to target a specific proxy
in the request chain (see Section 9.5). If no Max-Forwards field is in the request chain (see Section 9.6). If no Max-Forwards field is
present in the request, then the forwarded request MUST NOT include a present in the request, then the forwarded request MUST NOT include a
Max-Forwards field. Max-Forwards field.
7.3. GET 6.3. GET
The GET method requests transfer of a current representation of the The GET method requests transfer of a current representation of the
target resource. target resource.
If the target resource is a data-producing process, it is the If the target resource is a data-producing process, it is the
produced data which shall be returned as the representation in the produced data which shall be returned as the representation in the
response and not the source text of the process, unless that text response and not the source text of the process, unless that text
happens to be the output of the process. happens to be the output of the process.
The semantics of the GET method change to a "conditional GET" if the The semantics of the GET method change to a "conditional GET" if the
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Bodies on GET requests have no defined semantics. Note that sending Bodies on GET requests have no defined semantics. Note that sending
a body on a GET request might cause some existing implementations to a body on a GET request might cause some existing implementations to
reject the request. reject the request.
The response to a GET request is cacheable and MAY be used to satisfy The response to a GET request is cacheable and MAY be used to satisfy
subsequent GET and HEAD requests (see [Part6]). subsequent GET and HEAD requests (see [Part6]).
See Section 11.2 for security considerations when used for forms. See Section 11.2 for security considerations when used for forms.
7.4. HEAD 6.4. HEAD
The HEAD method is identical to GET except that the server MUST NOT The HEAD method is identical to GET except that the server MUST NOT
return a message-body in the response. The metadata contained in the return a message-body in the response. The metadata contained in the
HTTP header fields in response to a HEAD request SHOULD be identical HTTP header fields in response to a HEAD request SHOULD be identical
to the information sent in response to a GET request. This method to the information sent in response to a GET request. This method
can be used for obtaining metadata about the representation implied can be used for obtaining metadata about the representation implied
by the request without transferring the representation body. This by the request without transferring the representation body. This
method is often used for testing hypertext links for validity, method is often used for testing hypertext links for validity,
accessibility, and recent modification. accessibility, and recent modification.
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to update a previously cached representation from that resource; if to update a previously cached representation from that resource; if
the new field values indicate that the cached representation differs the new field values indicate that the cached representation differs
from the current representation (as would be indicated by a change in from the current representation (as would be indicated by a change in
Content-Length, ETag or Last-Modified), then the cache MUST treat the Content-Length, ETag or Last-Modified), then the cache MUST treat the
cache entry as stale. cache entry as stale.
Bodies on HEAD requests have no defined semantics. Note that sending Bodies on HEAD requests have no defined semantics. Note that sending
a body on a HEAD request might cause some existing implementations to a body on a HEAD request might cause some existing implementations to
reject the request. reject the request.
7.5. POST 6.5. POST
The POST method requests that the origin server accept the The POST method requests that the origin server accept the
representation enclosed in the request as data to be processed by the representation enclosed in the request as data to be processed by the
target resource. POST is designed to allow a uniform method to cover target resource. POST is designed to allow a uniform method to cover
the following functions: the following functions:
o Annotation of existing resources; o Annotation of existing resources;
o Posting a message to a bulletin board, newsgroup, mailing list, or o Posting a message to a bulletin board, newsgroup, mailing list, or
similar group of articles; similar group of articles;
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The action performed by the POST method might not result in a The action performed by the POST method might not result in a
resource that can be identified by a URI. In this case, either 200 resource that can be identified by a URI. In this case, either 200
(OK) or 204 (No Content) is the appropriate response status code, (OK) or 204 (No Content) is the appropriate response status code,
depending on whether or not the response includes a representation depending on whether or not the response includes a representation
that describes the result. that describes the result.
If a resource has been created on the origin server, the response If a resource has been created on the origin server, the response
SHOULD be 201 (Created) and contain a representation which describes SHOULD be 201 (Created) and contain a representation which describes
the status of the request and refers to the new resource, and a the status of the request and refers to the new resource, and a
Location header field (see Section 9.4). Location header field (see Section 9.5).
Responses to POST requests are only cacheable when they include Responses to POST requests are only cacheable when they include
explicit freshness information (see Section 2.3.1 of [Part6]). A explicit freshness information (see Section 2.3.1 of [Part6]). A
cached POST response with a Content-Location header field (see cached POST response with a Content-Location header field (see
Section 6.7 of [Part3]) whose value is the effective Request URI MAY Section 6.7 of [Part3]) whose value is the effective Request URI MAY
be used to satisfy subsequent GET and HEAD requests. be used to satisfy subsequent GET and HEAD requests.
Note that POST caching is not widely implemented. However, the 303 Note that POST caching is not widely implemented. However, the 303
(See Other) response can be used to direct the user agent to retrieve (See Other) response can be used to direct the user agent to retrieve
a cacheable resource. a cacheable resource.
7.6. PUT 6.6. PUT
The PUT method requests that the state of the target resource be The PUT method requests that the state of the target resource be
created or replaced with the state defined by the representation created or replaced with the state defined by the representation
enclosed in the request message payload. A successful PUT of a given enclosed in the request message payload. A successful PUT of a given
representation would suggest that a subsequent GET on that same representation would suggest that a subsequent GET on that same
target resource will result in an equivalent representation being target resource will result in an equivalent representation being
returned in a 200 (OK) response. However, there is no guarantee that returned in a 200 (OK) response. However, there is no guarantee that
such a state change will be observable, since the target resource such a state change will be observable, since the target resource
might be acted upon by other user agents in parallel, or might be might be acted upon by other user agents in parallel, or might be
subject to dynamic processing by the origin server, before any subject to dynamic processing by the origin server, before any
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by targeting a separately identified resource with state that by targeting a separately identified resource with state that
overlaps a portion of the larger resource, or by using a different overlaps a portion of the larger resource, or by using a different
method that has been specifically defined for partial updates (for method that has been specifically defined for partial updates (for
example, the PATCH method defined in [RFC5789]). example, the PATCH method defined in [RFC5789]).
Responses to the PUT method are not cacheable. If a PUT request Responses to the PUT method are not cacheable. If a PUT request
passes through a cache that has one or more stored responses for the passes through a cache that has one or more stored responses for the
effective request URI, those stored responses will be invalidated effective request URI, those stored responses will be invalidated
(see Section 2.5 of [Part6]). (see Section 2.5 of [Part6]).
7.7. DELETE 6.7. DELETE
The DELETE method requests that the origin server delete the target The DELETE method requests that the origin server delete the target
resource. This method MAY be overridden by human intervention (or resource. This method MAY be overridden by human intervention (or
other means) on the origin server. The client cannot be guaranteed other means) on the origin server. The client cannot be guaranteed
that the operation has been carried out, even if the status code that the operation has been carried out, even if the status code
returned from the origin server indicates that the action has been returned from the origin server indicates that the action has been
completed successfully. However, the server SHOULD NOT indicate completed successfully. However, the server SHOULD NOT indicate
success unless, at the time the response is given, it intends to success unless, at the time the response is given, it intends to
delete the resource or move it to an inaccessible location. delete the resource or move it to an inaccessible location.
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Bodies on DELETE requests have no defined semantics. Note that Bodies on DELETE requests have no defined semantics. Note that
sending a body on a DELETE request might cause some existing sending a body on a DELETE request might cause some existing
implementations to reject the request. implementations to reject the request.
Responses to the DELETE method are not cacheable. If a DELETE Responses to the DELETE method are not cacheable. If a DELETE
request passes through a cache that has one or more stored responses request passes through a cache that has one or more stored responses
for the effective request URI, those stored responses will be for the effective request URI, those stored responses will be
invalidated (see Section 2.5 of [Part6]). invalidated (see Section 2.5 of [Part6]).
7.8. TRACE 6.8. TRACE
The TRACE method requests a remote, application-layer loop-back of The TRACE method requests a remote, application-layer loop-back of
the request message. The final recipient of the request SHOULD the request message. The final recipient of the request SHOULD
reflect the message received back to the client as the message-body reflect the message received back to the client as the message-body
of a 200 (OK) response. The final recipient is either the origin of a 200 (OK) response. The final recipient is either the origin
server or the first proxy to receive a Max-Forwards value of zero (0) server or the first proxy to receive a Max-Forwards value of zero (0)
in the request (see Section 9.5). A TRACE request MUST NOT include a in the request (see Section 9.6). A TRACE request MUST NOT include a
message-body. message-body.
TRACE allows the client to see what is being received at the other TRACE allows the client to see what is being received at the other
end of the request chain and use that data for testing or diagnostic end of the request chain and use that data for testing or diagnostic
information. The value of the Via header field (Section 9.9 of information. The value of the Via header field (Section 8.8 of
[Part1]) is of particular interest, since it acts as a trace of the [Part1]) is of particular interest, since it acts as a trace of the
request chain. Use of the Max-Forwards header field allows the request chain. Use of the Max-Forwards header field allows the
client to limit the length of the request chain, which is useful for client to limit the length of the request chain, which is useful for
testing a chain of proxies forwarding messages in an infinite loop. testing a chain of proxies forwarding messages in an infinite loop.
If the request is valid, the response SHOULD have a Content-Type of If the request is valid, the response SHOULD have a Content-Type of
"message/http" (see Section 10.3.1 of [Part1]) and contain a message- "message/http" (see Section 9.3.1 of [Part1]) and contain a message-
body that encloses a copy of the entire request message. Responses body that encloses a copy of the entire request message. Responses
to the TRACE method are not cacheable. to the TRACE method are not cacheable.
7.9. CONNECT 6.9. CONNECT
The CONNECT method requests that the proxy establish a tunnel to the The CONNECT method requests that the proxy establish a tunnel to the
request-target and then restrict its behavior to blind forwarding of request-target and then restrict its behavior to blind forwarding of
packets until the connection is closed. packets until the connection is closed.
When using CONNECT, the request-target MUST use the authority form When using CONNECT, the request-target MUST use the authority form
(Section 4.1.2 of [Part1]); i.e., the request-target consists of only (Section 3.1.1.2 of [Part1]); i.e., the request-target consists of
the host name and port number of the tunnel destination, separated by only the host name and port number of the tunnel destination,
a colon. For example, separated by a colon. For example,
CONNECT server.example.com:80 HTTP/1.1 CONNECT server.example.com:80 HTTP/1.1
Host: server.example.com:80 Host: server.example.com:80
Other HTTP mechanisms can be used normally with the CONNECT method -- Other HTTP mechanisms can be used normally with the CONNECT method --
except end-to-end protocol Upgrade requests, since the tunnel must be except end-to-end protocol Upgrade requests, since the tunnel must be
established first. established first.
For example, proxy authentication might be used to establish the For example, proxy authentication might be used to establish the
authority to create a tunnel: authority to create a tunnel:
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Bodies on CONNECT requests have no defined semantics. Note that Bodies on CONNECT requests have no defined semantics. Note that
sending a body on a CONNECT request might cause some existing sending a body on a CONNECT request might cause some existing
implementations to reject the request. implementations to reject the request.
Like any other pipelined HTTP/1.1 request, data to be tunnel may be Like any other pipelined HTTP/1.1 request, data to be tunnel may be
sent immediately after the blank line. The usual caveats also apply: sent immediately after the blank line. The usual caveats also apply:
data may be discarded if the eventual response is negative, and the data may be discarded if the eventual response is negative, and the
connection may be reset with no response if more than one TCP segment connection may be reset with no response if more than one TCP segment
is outstanding. is outstanding.
7.9.1. Establishing a Tunnel with CONNECT 6.9.1. Establishing a Tunnel with CONNECT
Any successful (2xx) response to a CONNECT request indicates that the Any successful (2xx) response to a CONNECT request indicates that the
proxy has established a connection to the requested host and port, proxy has established a connection to the requested host and port,
and has switched to tunneling the current connection to that server and has switched to tunneling the current connection to that server
connection. connection.
It may be the case that the proxy itself can only reach the requested It may be the case that the proxy itself can only reach the requested
origin server through another proxy. In this case, the first proxy origin server through another proxy. In this case, the first proxy
SHOULD make a CONNECT request of that next proxy, requesting a tunnel SHOULD make a CONNECT request of that next proxy, requesting a tunnel
to the authority. A proxy MUST NOT respond with any 2xx status code to the authority. A proxy MUST NOT respond with any 2xx status code
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An origin server which receives a CONNECT request for itself MAY An origin server which receives a CONNECT request for itself MAY
respond with a 2xx status code to indicate that a connection is respond with a 2xx status code to indicate that a connection is
established. established.
If at any point either one of the peers gets disconnected, any If at any point either one of the peers gets disconnected, any
outstanding data that came from that peer will be passed to the other outstanding data that came from that peer will be passed to the other
one, and after that also the other connection will be terminated by one, and after that also the other connection will be terminated by
the proxy. If there is outstanding data to that peer undelivered, the proxy. If there is outstanding data to that peer undelivered,
that data will be discarded. that data will be discarded.
8. Status Code Definitions 7. Status Code Definitions
The first digit of the Status-Code defines the class of response.
The last two digits do not have any categorization role. There are 5
values for the first digit:
o 1xx: Informational - Request received, continuing process
o 2xx: Success - The action was successfully received, understood,
and accepted
o 3xx: Redirection - Further action must be taken in order to
complete the request
o 4xx: Client Error - The request contains bad syntax or cannot be
fulfilled
o 5xx: Server Error - The server failed to fulfill an apparently
valid request
Each Status-Code is described below, including any metadata required Each Status-Code is described below, including any metadata required
in the response. in the response.
8.1. Informational 1xx 7.1. Informational 1xx
This class of status code indicates a provisional response, This class of status code indicates a provisional response,
consisting only of the Status-Line and optional header fields, and is consisting only of the Status-Line and optional header fields, and is
terminated by an empty line. There are no required header fields for terminated by an empty line. There are no required header fields for
this class of status code. Since HTTP/1.0 did not define any 1xx this class of status code. Since HTTP/1.0 did not define any 1xx
status codes, servers MUST NOT send a 1xx response to an HTTP/1.0 status codes, servers MUST NOT send a 1xx response to an HTTP/1.0
client except under experimental conditions. client except under experimental conditions.
A client MUST be prepared to accept one or more 1xx status responses A client MUST be prepared to accept one or more 1xx status responses
prior to a regular response, even if the client does not expect a 100 prior to a regular response, even if the client does not expect a 100
(Continue) status message. Unexpected 1xx status responses MAY be (Continue) status message. Unexpected 1xx status responses MAY be
ignored by a user agent. ignored by a user agent.
Proxies MUST forward 1xx responses, unless the connection between the Proxies MUST forward 1xx responses, unless the connection between the
proxy and its client has been closed, or unless the proxy itself proxy and its client has been closed, or unless the proxy itself
requested the generation of the 1xx response. (For example, if a requested the generation of the 1xx response. (For example, if a
proxy adds a "Expect: 100-continue" field when it forwards a request, proxy adds a "Expect: 100-continue" field when it forwards a request,
then it need not forward the corresponding 100 (Continue) then it need not forward the corresponding 100 (Continue)
response(s).) response(s).)
8.1.1. 100 Continue 7.1.1. 100 Continue
The client SHOULD continue with its request. This interim response The client SHOULD continue with its request. This interim response
is used to inform the client that the initial part of the request has is used to inform the client that the initial part of the request has
been received and has not yet been rejected by the server. The been received and has not yet been rejected by the server. The
client SHOULD continue by sending the remainder of the request or, if client SHOULD continue by sending the remainder of the request or, if
the request has already been completed, ignore this response. The the request has already been completed, ignore this response. The
server MUST send a final response after the request has been server MUST send a final response after the request has been
completed. See Section 7.2.3 of [Part1] for detailed discussion of completed. See Section 6.2.3 of [Part1] for detailed discussion of
the use and handling of this status code. the use and handling of this status code.
8.1.2. 101 Switching Protocols 7.1.2. 101 Switching Protocols
The server understands and is willing to comply with the client's The server understands and is willing to comply with the client's
request, via the Upgrade message header field (Section 9.8 of request, via the Upgrade message header field (Section 8.7 of
[Part1]), for a change in the application protocol being used on this [Part1]), for a change in the application protocol being used on this
connection. The server will switch protocols to those defined by the connection. The server will switch protocols to those defined by the
response's Upgrade header field immediately after the empty line response's Upgrade header field immediately after the empty line
which terminates the 101 response. which terminates the 101 response.
The protocol SHOULD be switched only when it is advantageous to do The protocol SHOULD be switched only when it is advantageous to do
so. For example, switching to a newer version of HTTP is so. For example, switching to a newer version of HTTP is
advantageous over older versions, and switching to a real-time, advantageous over older versions, and switching to a real-time,
synchronous protocol might be advantageous when delivering resources synchronous protocol might be advantageous when delivering resources
that use such features. that use such features.
8.2. Successful 2xx 7.2. Successful 2xx
This class of status code indicates that the client's request was This class of status code indicates that the client's request was
successfully received, understood, and accepted. successfully received, understood, and accepted.
8.2.1. 200 OK 7.2.1. 200 OK
The request has succeeded. The payload returned with the response is The request has succeeded. The payload returned with the response is
dependent on the method used in the request, for example: dependent on the method used in the request, for example:
GET a representation of the target resource is sent in the response; GET a representation of the target resource is sent in the response;
HEAD the same representation as GET, except without the message- HEAD the same representation as GET, except without the message-
body; body;
POST a representation describing or containing the result of the POST a representation describing or containing the result of the
action; action;
TRACE a representation containing the request message as received by TRACE a representation containing the request message as received by
the end server. the end server.
Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to
determine freshness for 200 responses. determine freshness for 200 responses.
8.2.2. 201 Created 7.2.2. 201 Created
The request has been fulfilled and has resulted in a new resource The request has been fulfilled and has resulted in a new resource
being created. The newly created resource can be referenced by the being created. The newly created resource can be referenced by the
URI(s) returned in the payload of the response, with the most URI(s) returned in the payload of the response, with the most
specific URI for the resource given by a Location header field. The specific URI for the resource given by a Location header field. The
response SHOULD include a payload containing a list of resource response SHOULD include a payload containing a list of resource
characteristics and location(s) from which the user or user agent can characteristics and location(s) from which the user or user agent can
choose the one most appropriate. The payload format is specified by choose the one most appropriate. The payload format is specified by
the media type given in the Content-Type header field. The origin the media type given in the Content-Type header field. The origin
server MUST create the resource before returning the 201 status code. server MUST create the resource before returning the 201 status code.
If the action cannot be carried out immediately, the server SHOULD If the action cannot be carried out immediately, the server SHOULD
respond with 202 (Accepted) response instead. respond with 202 (Accepted) response instead.
A 201 response MAY contain an ETag response header field indicating A 201 response MAY contain an ETag response header field indicating
the current value of the entity-tag for the representation of the the current value of the entity-tag for the representation of the
resource just created (see Section 2.3 of [Part4]). resource just created (see Section 2.3 of [Part4]).
8.2.3. 202 Accepted 7.2.3. 202 Accepted
The request has been accepted for processing, but the processing has The request has been accepted for processing, but the processing has
not been completed. The request might or might not eventually be not been completed. The request might or might not eventually be
acted upon, as it might be disallowed when processing actually takes acted upon, as it might be disallowed when processing actually takes
place. There is no facility for re-sending a status code from an place. There is no facility for re-sending a status code from an
asynchronous operation such as this. asynchronous operation such as this.
The 202 response is intentionally non-committal. Its purpose is to The 202 response is intentionally non-committal. Its purpose is to
allow a server to accept a request for some other process (perhaps a allow a server to accept a request for some other process (perhaps a
batch-oriented process that is only run once per day) without batch-oriented process that is only run once per day) without
requiring that the user agent's connection to the server persist requiring that the user agent's connection to the server persist
until the process is completed. The representation returned with until the process is completed. The representation returned with
this response SHOULD include an indication of the request's current this response SHOULD include an indication of the request's current
status and either a pointer to a status monitor or some estimate of status and either a pointer to a status monitor or some estimate of
when the user can expect the request to be fulfilled. when the user can expect the request to be fulfilled.
8.2.4. 203 Non-Authoritative Information 7.2.4. 203 Non-Authoritative Information
The representation in the response has been transformed or otherwise The representation in the response has been transformed or otherwise
modified by a transforming proxy (Section 2.4 of [Part1]). Note that modified by a transforming proxy (Section 2.4 of [Part1]). Note that
the behaviour of transforming intermediaries is controlled by the no- the behaviour of transforming intermediaries is controlled by the no-
transform Cache-Control directive (Section 3.2 of [Part6]). transform Cache-Control directive (Section 3.2 of [Part6]).
This status code is only appropriate when the response status code This status code is only appropriate when the response status code
would have been 200 (OK) otherwise. When the status code before would have been 200 (OK) otherwise. When the status code before
transformation would have been different, the 214 Transformation transformation would have been different, the 214 Transformation
Applied warn-code (Section 3.6 of [Part6]) is appropriate. Applied warn-code (Section 3.6 of [Part6]) is appropriate.
Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to
determine freshness for 203 responses. determine freshness for 203 responses.
8.2.5. 204 No Content 7.2.5. 204 No Content
The 204 (No Content) status code indicates that the server has The 204 (No Content) status code indicates that the server has
successfully fulfilled the request and that there is no additional successfully fulfilled the request and that there is no additional
content to return in the response payload body. Metadata in the content to return in the response payload body. Metadata in the
response header fields refer to the target resource and its current response header fields refer to the target resource and its current
representation after the requested action. representation after the requested action.
For example, if a 204 status code is received in response to a PUT For example, if a 204 status code is received in response to a PUT
request and the response contains an ETag header field, then the PUT request and the response contains an ETag header field, then the PUT
was successful and the ETag field-value contains the entity-tag for was successful and the ETag field-value contains the entity-tag for
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For example, a 204 status code is commonly used with document editing For example, a 204 status code is commonly used with document editing
interfaces corresponding to a "save" action, such that the document interfaces corresponding to a "save" action, such that the document
being saved remains available to the user for editing. It is also being saved remains available to the user for editing. It is also
frequently used with interfaces that expect automated data transfers frequently used with interfaces that expect automated data transfers
to be prevalent, such as within distributed version control systems. to be prevalent, such as within distributed version control systems.
The 204 response MUST NOT include a message-body, and thus is always The 204 response MUST NOT include a message-body, and thus is always
terminated by the first empty line after the header fields. terminated by the first empty line after the header fields.
8.2.6. 205 Reset Content 7.2.6. 205 Reset Content
The server has fulfilled the request and the user agent SHOULD reset The server has fulfilled the request and the user agent SHOULD reset
the document view which caused the request to be sent. This response the document view which caused the request to be sent. This response
is primarily intended to allow input for actions to take place via is primarily intended to allow input for actions to take place via
user input, followed by a clearing of the form in which the input is user input, followed by a clearing of the form in which the input is
given so that the user can easily initiate another input action. given so that the user can easily initiate another input action.
The message-body included with the response MUST be empty. Note that The message-body included with the response MUST be empty. Note that
receivers still need to parse the response according to the algorithm receivers still need to parse the response according to the algorithm
defined in Section 3.3 of [Part1]. defined in Section 3.3 of [Part1].
8.2.7. 206 Partial Content 7.2.7. 206 Partial Content
The server has fulfilled the partial GET request for the resource and The server has fulfilled the partial GET request for the resource and
the enclosed payload is a partial representation as defined in the enclosed payload is a partial representation as defined in
Section 3.1 of [Part5]. Section 3.1 of [Part5].
Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to
determine freshness for 206 responses. determine freshness for 206 responses.
8.3. Redirection 3xx 7.3. Redirection 3xx
This class of status code indicates that further action needs to be This class of status code indicates that further action needs to be
taken by the user agent in order to fulfill the request. The action taken by the user agent in order to fulfill the request. If the
required MAY be carried out by the user agent without interaction required action involves a subsequent HTTP request, it MAY be carried
with the user if and only if the method used in the second request is out by the user agent without interaction with the user if and only
known to be "safe", as defined in Section 7.1.1. A client SHOULD if the method used in the second request is known to be "safe", as
detect infinite redirection loops, since such loops generate network defined in Section 6.1.1.
traffic for each redirection.
There are several types of redirects:
1. Redirects of the request to another URI, either temporarily or
permanently. The new URI is specified in the Location header
field. In this specification, the status codes 301 (Moved
Permanently), 302 (Found), and 307 (Temporary Redirect) fall
under this category.
2. Redirection to a new location that represents an indirect
response to the request, such as the result of a POST operation
to be retrieved with a subsequent GET request. This is status
code 303 (See Other).
3. Redirection offering a choice of matching resources for use by
agent-driven content negotiation (Section 5.2 of [Part3]). This
is status code 300 (Multiple Choices).
4. Other kinds of redirection, such as to a cached result (status
code 304 (Not Modified)).
Note: In HTTP/1.0, only the status codes 301 (Moved Permanently)
and 302 (Found) were defined for the first type of redirect, and
the second type did not exist at all ([RFC1945], Section 9.3).
However it turned out that web forms using POST expected redirects
to change the operation for the subsequent request to retrieval
(GET). To address this use case, HTTP/1.1 introduced the second
type of redirect with the status code 303 (See Other) ([RFC2068],
Section 10.3.4). As user agents did not change their behavior to
maintain backwards compatibility, the first revision of HTTP/1.1
added yet another status code, 307 (Temporary Redirect), for which
the backwards compatibility problems did not apply ([RFC2616],
Section 10.3.8). Over 10 years later, most user agents still do
method rewriting for status codes 301 and 302, therefore this
specification makes that behavior compliant in case the original
request was POST.
Clients SHOULD detect and intervene in cyclical redirections (i.e.,
"infinite" redirection loops).
Note: An earlier version of this specification recommended a Note: An earlier version of this specification recommended a
maximum of five redirections ([RFC2068], Section 10.3). Content maximum of five redirections ([RFC2068], Section 10.3). Content
developers need to be aware that some clients might implement such developers need to be aware that some clients might implement such
a fixed limitation. a fixed limitation.
8.3.1. 300 Multiple Choices 7.3.1. 300 Multiple Choices
The target resource has more than one representation, each with its The target resource has more than one representation, each with its
own specific location, and agent-driven negotiation information own specific location, and agent-driven negotiation information
(Section 5 of [Part3]) is being provided so that the user (or user (Section 5 of [Part3]) is being provided so that the user (or user
agent) can select a preferred representation by redirecting its agent) can select a preferred representation by redirecting its
request to that location. request to that location.
Unless it was a HEAD request, the response SHOULD include a Unless it was a HEAD request, the response SHOULD include a
representation containing a list of representation metadata and representation containing a list of representation metadata and
location(s) from which the user or user agent can choose the one most location(s) from which the user or user agent can choose the one most
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does not define any standard for such automatic selection. does not define any standard for such automatic selection.
If the server has a preferred choice of representation, it SHOULD If the server has a preferred choice of representation, it SHOULD
include the specific URI for that representation in the Location include the specific URI for that representation in the Location
field; user agents MAY use the Location field value for automatic field; user agents MAY use the Location field value for automatic
redirection. redirection.
Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to
determine freshness for 300 responses. determine freshness for 300 responses.
8.3.2. 301 Moved Permanently 7.3.2. 301 Moved Permanently
The target resource has been assigned a new permanent URI and any The target resource has been assigned a new permanent URI and any
future references to this resource SHOULD use one of the returned future references to this resource SHOULD use one of the returned
URIs. Clients with link editing capabilities ought to automatically URIs. Clients with link editing capabilities ought to automatically
re-link references to the effective request URI to one or more of the re-link references to the effective request URI to one or more of the
new references returned by the server, where possible. new references returned by the server, where possible.
Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to
determine freshness for 301 responses. determine freshness for 301 responses.
The new permanent URI SHOULD be given by the Location field in the The new permanent URI SHOULD be given by the Location field in the
response. Unless the request method was HEAD, the representation of response. Unless the request method was HEAD, the representation of
the response SHOULD contain a short hypertext note with a hyperlink the response SHOULD contain a short hypertext note with a hyperlink
to the new URI(s). to the new URI(s).
If the 301 status code is received in response to a request method If the 301 status code is received in response to a request method
that is known to be "safe", as defined in Section 7.1.1, then the that is known to be "safe", as defined in Section 6.1.1, then the
request MAY be automatically redirected by the user agent without request MAY be automatically redirected by the user agent without
confirmation. Otherwise, the user agent MUST NOT automatically confirmation. Otherwise, the user agent MUST NOT automatically
redirect the request unless it can be confirmed by the user, since redirect the request unless it can be confirmed by the user, since
this might change the conditions under which the request was issued. this might change the conditions under which the request was issued.
Note: When automatically redirecting a POST request after Note: For historic reasons, user agents MAY change the request
receiving a 301 status code, some existing HTTP/1.0 user agents method from POST to GET for the subsequent request. If this
will erroneously change it into a GET request. behavior is undesired, status code 307 (Temporary Redirect) can be
used instead.
8.3.3. 302 Found 7.3.3. 302 Found
The target resource resides temporarily under a different URI. Since The target resource resides temporarily under a different URI. Since
the redirection might be altered on occasion, the client SHOULD the redirection might be altered on occasion, the client SHOULD
continue to use the effective request URI for future requests. continue to use the effective request URI for future requests.
The temporary URI SHOULD be given by the Location field in the The temporary URI SHOULD be given by the Location field in the
response. Unless the request method was HEAD, the representation of response. Unless the request method was HEAD, the representation of
the response SHOULD contain a short hypertext note with a hyperlink the response SHOULD contain a short hypertext note with a hyperlink
to the new URI(s). to the new URI(s).
If the 302 status code is received in response to a request method If the 302 status code is received in response to a request method
that is known to be "safe", as defined in Section 7.1.1, then the that is known to be "safe", as defined in Section 6.1.1, then the
request MAY be automatically redirected by the user agent without request MAY be automatically redirected by the user agent without
confirmation. Otherwise, the user agent MUST NOT automatically confirmation. Otherwise, the user agent MUST NOT automatically
redirect the request unless it can be confirmed by the user, since redirect the request unless it can be confirmed by the user, since
this might change the conditions under which the request was issued. this might change the conditions under which the request was issued.
Note: HTTP/1.0 ([RFC1945], Section 9.3) and the first version of Note: For historic reasons, user agents MAY change the request
HTTP/1.1 ([RFC2068], Section 10.3.3) specify that the client is method from POST to GET for the subsequent request. If this
not allowed to change the method on the redirected request. behavior is undesired, status code 307 (Temporary Redirect) can be
However, most existing user agent implementations treat 302 as if used instead. [[issue312: but see
it were a 303 response, performing a GET on the Location field- <http://trac.tools.ietf.org/wg/httpbis/trac/ticket/312>]]
value regardless of the original request method. Therefore, a
previous version of this specification ([RFC2616], Section 10.3.3)
has added the status codes 303 and 307 for servers that wish to
make unambiguously clear which kind of reaction is expected of the
client.
8.3.4. 303 See Other 7.3.4. 303 See Other
The server directs the user agent to a different resource, indicated The 303 status code indicates that the server is redirecting the user
by a URI in the Location header field, that provides an indirect agent to a different resource, as indicated by a URI in the Location
response to the original request. The user agent MAY perform a GET header field, that is intended to provide an indirect response to the
request on the URI in the Location field in order to obtain a original request. In order to satisfy the original request, a user
representation corresponding to the response, be redirected again, or agent SHOULD perform a retrieval request using the Location URI (a
end with an error status. The Location URI is not a substitute GET or HEAD request if using HTTP), which may itself be redirected
reference for the effective request URI. further, and present the eventual result as an answer to the original
request. Note that the new URI in the Location header field is not
considered equivalent to the effective request URI.
The 303 status code is generally applicable to any HTTP method. It This status code is generally applicable to any HTTP method. It is
is primarily used to allow the output of a POST action to redirect primarily used to allow the output of a POST action to redirect the
the user agent to a selected resource, since doing so provides the user agent to a selected resource, since doing so provides the
information corresponding to the POST response in a form that can be information corresponding to the POST response in a form that can be
separately identified, bookmarked, and cached independent of the separately identified, bookmarked, and cached independent of the
original request. original request.
A 303 response to a GET request indicates that the requested resource A 303 response to a GET request indicates that the requested resource
does not have a representation of its own that can be transferred by does not have a representation of its own that can be transferred by
the server over HTTP. The Location URI indicates a resource that is the server over HTTP. The Location URI indicates a resource that is
descriptive of the target resource, such that the follow-on descriptive of the target resource, such that the follow-on
representation might be useful to recipients without implying that it representation might be useful to recipients without implying that it
adequately represents the target resource. Note that answers to the adequately represents the target resource. Note that answers to the
questions of what can be represented, what representations are questions of what can be represented, what representations are
adequate, and what might be a useful description are outside the adequate, and what might be a useful description are outside the
scope of HTTP and thus entirely determined by the URI owner(s). scope of HTTP and thus entirely determined by the URI owner(s).
Except for responses to a HEAD request, the representation of a 303 Except for responses to a HEAD request, the representation of a 303
response SHOULD contain a short hypertext note with a hyperlink to response SHOULD contain a short hypertext note with a hyperlink to
the Location URI. the Location URI.
8.3.5. 304 Not Modified 7.3.5. 304 Not Modified
The response to the request has not been modified since the The response to the request has not been modified since the
conditions indicated by the client's conditional GET request, as conditions indicated by the client's conditional GET request, as
defined in Section 4.1 of [Part4]. defined in Section 4.1 of [Part4].
8.3.6. 305 Use Proxy 7.3.6. 305 Use Proxy
The 305 status code was defined in a previous version of this The 305 status code was defined in a previous version of this
specification (see Appendix A), and is now deprecated. specification (see Appendix A), and is now deprecated.
8.3.7. 306 (Unused) 7.3.7. 306 (Unused)
The 306 status code was used in a previous version of the The 306 status code was used in a previous version of the
specification, is no longer used, and the code is reserved. specification, is no longer used, and the code is reserved.
8.3.8. 307 Temporary Redirect 7.3.8. 307 Temporary Redirect
The target resource resides temporarily under a different URI. Since The target resource resides temporarily under a different URI. Since
the redirection can change over time, the client SHOULD continue to the redirection can change over time, the client SHOULD continue to
use the effective request URI for future requests. use the effective request URI for future requests.
The temporary URI SHOULD be given by the Location field in the The temporary URI SHOULD be given by the Location field in the
response. Unless the request method was HEAD, the representation of response. Unless the request method was HEAD, the representation of
the response SHOULD contain a short hypertext note with a hyperlink the response SHOULD contain a short hypertext note with a hyperlink
to the new URI(s), since many pre-HTTP/1.1 user agents do not to the new URI(s), since many pre-HTTP/1.1 user agents do not
understand the 307 status code. Therefore, the note SHOULD contain understand the 307 status code. Therefore, the note SHOULD contain
the information necessary for a user to repeat the original request the information necessary for a user to repeat the original request
on the new URI. on the new URI.
If the 307 status code is received in response to a request method If the 307 status code is received in response to a request method
that is known to be "safe", as defined in Section 7.1.1, then the that is known to be "safe", as defined in Section 6.1.1, then the
request MAY be automatically redirected by the user agent without request MAY be automatically redirected by the user agent without
confirmation. Otherwise, the user agent MUST NOT automatically confirmation. Otherwise, the user agent MUST NOT automatically
redirect the request unless it can be confirmed by the user, since redirect the request unless it can be confirmed by the user, since
this might change the conditions under which the request was issued. this might change the conditions under which the request was issued.
8.4. Client Error 4xx 7.4. Client Error 4xx
The 4xx class of status code is intended for cases in which the The 4xx class of status code is intended for cases in which the
client seems to have erred. Except when responding to a HEAD client seems to have erred. Except when responding to a HEAD
request, the server SHOULD include a representation containing an request, the server SHOULD include a representation containing an
explanation of the error situation, and whether it is a temporary or explanation of the error situation, and whether it is a temporary or
permanent condition. These status codes are applicable to any permanent condition. These status codes are applicable to any
request method. User agents SHOULD display any included request method. User agents SHOULD display any included
representation to the user. representation to the user.
If the client is sending data, a server implementation using TCP If the client is sending data, a server implementation using TCP
SHOULD be careful to ensure that the client acknowledges receipt of SHOULD be careful to ensure that the client acknowledges receipt of
the packet(s) containing the response, before the server closes the the packet(s) containing the response, before the server closes the
input connection. If the client continues sending data to the server input connection. If the client continues sending data to the server
after the close, the server's TCP stack will send a reset packet to after the close, the server's TCP stack will send a reset packet to
the client, which might erase the client's unacknowledged input the client, which might erase the client's unacknowledged input
buffers before they can be read and interpreted by the HTTP buffers before they can be read and interpreted by the HTTP
application. application.
8.4.1. 400 Bad Request 7.4.1. 400 Bad Request
The server cannot or will not process the request, due to a client The server cannot or will not process the request, due to a client
error (e.g., malformed syntax). error (e.g., malformed syntax).
8.4.2. 401 Unauthorized 7.4.2. 401 Unauthorized
The request requires user authentication (see Section 3.1 of The request requires user authentication (see Section 3.1 of
[Part7]). [Part7]).
8.4.3. 402 Payment Required 7.4.3. 402 Payment Required
This code is reserved for future use. This code is reserved for future use.
8.4.4. 403 Forbidden 7.4.4. 403 Forbidden
The server understood the request, but refuses to authorize it. The server understood the request, but refuses to authorize it.
Providing different user authentication credentials might be Providing different user authentication credentials might be
successful, but any credentials that were provided in the request are successful, but any credentials that were provided in the request are
insufficient. The request SHOULD NOT be repeated with the same insufficient. The request SHOULD NOT be repeated with the same
credentials. credentials.
If the request method was not HEAD and the server wishes to make If the request method was not HEAD and the server wishes to make
public why the request has not been fulfilled, it SHOULD describe the public why the request has not been fulfilled, it SHOULD describe the
reason for the refusal in the representation. If the server does not reason for the refusal in the representation. If the server does not
wish to make this information available to the client, the status wish to make this information available to the client, the status
code 404 (Not Found) MAY be used instead. code 404 (Not Found) MAY be used instead.
8.4.5. 404 Not Found 7.4.5. 404 Not Found
The server has not found anything matching the effective request URI. The server has not found anything matching the effective request URI.
No indication is given of whether the condition is temporary or No indication is given of whether the condition is temporary or
permanent. The 410 (Gone) status code SHOULD be used if the server permanent. The 410 (Gone) status code SHOULD be used if the server
knows, through some internally configurable mechanism, that an old knows, through some internally configurable mechanism, that an old
resource is permanently unavailable and has no forwarding address. resource is permanently unavailable and has no forwarding address.
This status code is commonly used when the server does not wish to This status code is commonly used when the server does not wish to
reveal exactly why the request has been refused, or when no other reveal exactly why the request has been refused, or when no other
response is applicable. response is applicable.
8.4.6. 405 Method Not Allowed 7.4.6. 405 Method Not Allowed
The method specified in the Request-Line is not allowed for the The method specified in the Request-Line is not allowed for the
target resource. The response MUST include an Allow header field target resource. The response MUST include an Allow header field
containing a list of valid methods for the requested resource. containing a list of valid methods for the requested resource.
8.4.7. 406 Not Acceptable 7.4.7. 406 Not Acceptable
The resource identified by the request is only capable of generating The resource identified by the request is only capable of generating
response representations which have content characteristics not response representations which have content characteristics not
acceptable according to the Accept and Accept-* header fields sent in acceptable according to the Accept and Accept-* header fields sent in
the request (see Section 6 of [Part3]). the request (see Section 6 of [Part3]).
Unless it was a HEAD request, the response SHOULD include a Unless it was a HEAD request, the response SHOULD include a
representation containing a list of available representation representation containing a list of available representation
characteristics and location(s) from which the user or user agent can characteristics and location(s) from which the user or user agent can
choose the one most appropriate. The data format is specified by the choose the one most appropriate. The data format is specified by the
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Note: HTTP/1.1 servers are allowed to return responses which are Note: HTTP/1.1 servers are allowed to return responses which are
not acceptable according to the accept header fields sent in the not acceptable according to the accept header fields sent in the
request. In some cases, this might even be preferable to sending request. In some cases, this might even be preferable to sending
a 406 response. User agents are encouraged to inspect the header a 406 response. User agents are encouraged to inspect the header
fields of an incoming response to determine if it is acceptable. fields of an incoming response to determine if it is acceptable.
If the response could be unacceptable, a user agent SHOULD If the response could be unacceptable, a user agent SHOULD
temporarily stop receipt of more data and query the user for a temporarily stop receipt of more data and query the user for a
decision on further actions. decision on further actions.
8.4.8. 407 Proxy Authentication Required 7.4.8. 407 Proxy Authentication Required
This code is similar to 401 (Unauthorized), but indicates that the This code is similar to 401 (Unauthorized), but indicates that the
client must first authenticate itself with the proxy (see Section 3.2 client must first authenticate itself with the proxy (see Section 3.2
of [Part7]). of [Part7]).
8.4.9. 408 Request Timeout 7.4.9. 408 Request Timeout
The client did not produce a request within the time that the server The client did not produce a request within the time that the server
was prepared to wait. The client MAY repeat the request without was prepared to wait. The client MAY repeat the request without
modifications at any later time. modifications at any later time.
8.4.10. 409 Conflict 7.4.10. 409 Conflict
The request could not be completed due to a conflict with the current The request could not be completed due to a conflict with the current
state of the resource. This code is only allowed in situations where state of the resource. This code is only allowed in situations where
it is expected that the user might be able to resolve the conflict it is expected that the user might be able to resolve the conflict
and resubmit the request. The response body SHOULD include enough and resubmit the request. The response body SHOULD include enough
information for the user to recognize the source of the conflict. information for the user to recognize the source of the conflict.
Ideally, the response representation would include enough information Ideally, the response representation would include enough information
for the user or user agent to fix the problem; however, that might for the user or user agent to fix the problem; however, that might
not be possible and is not required. not be possible and is not required.
Conflicts are most likely to occur in response to a PUT request. For Conflicts are most likely to occur in response to a PUT request. For
example, if versioning were being used and the representation being example, if versioning were being used and the representation being
PUT included changes to a resource which conflict with those made by PUT included changes to a resource which conflict with those made by
an earlier (third-party) request, the server might use the 409 an earlier (third-party) request, the server might use the 409
response to indicate that it can't complete the request. In this response to indicate that it can't complete the request. In this
case, the response representation would likely contain a list of the case, the response representation would likely contain a list of the
differences between the two versions in a format defined by the differences between the two versions in a format defined by the
response Content-Type. response Content-Type.
8.4.11. 410 Gone 7.4.11. 410 Gone
The target resource is no longer available at the server and no The target resource is no longer available at the server and no
forwarding address is known. This condition is expected to be forwarding address is known. This condition is expected to be
considered permanent. Clients with link editing capabilities SHOULD considered permanent. Clients with link editing capabilities SHOULD
delete references to the effective request URI after user approval. delete references to the effective request URI after user approval.
If the server does not know, or has no facility to determine, whether If the server does not know, or has no facility to determine, whether
or not the condition is permanent, the status code 404 (Not Found) or not the condition is permanent, the status code 404 (Not Found)
SHOULD be used instead. SHOULD be used instead.
The 410 response is primarily intended to assist the task of web The 410 response is primarily intended to assist the task of web
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remote links to that resource be removed. Such an event is common remote links to that resource be removed. Such an event is common
for limited-time, promotional services and for resources belonging to for limited-time, promotional services and for resources belonging to
individuals no longer working at the server's site. It is not individuals no longer working at the server's site. It is not
necessary to mark all permanently unavailable resources as "gone" or necessary to mark all permanently unavailable resources as "gone" or
to keep the mark for any length of time -- that is left to the to keep the mark for any length of time -- that is left to the
discretion of the server owner. discretion of the server owner.
Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to Caches MAY use a heuristic (see Section 2.3.1.1 of [Part6]) to
determine freshness for 410 responses. determine freshness for 410 responses.
8.4.12. 411 Length Required 7.4.12. 411 Length Required
The server refuses to accept the request without a defined Content- The server refuses to accept the request without a defined Content-
Length. The client MAY repeat the request if it adds a valid Length. The client MAY repeat the request if it adds a valid
Content-Length header field containing the length of the message-body Content-Length header field containing the length of the message-body
in the request message. in the request message.
8.4.13. 412 Precondition Failed 7.4.13. 412 Precondition Failed
The precondition given in one or more of the header fields evaluated The precondition given in one or more of the header fields evaluated
to false when it was tested on the server, as defined in Section 4.2 to false when it was tested on the server, as defined in Section 4.2
of [Part4]. of [Part4].
8.4.14. 413 Request Representation Too Large 7.4.14. 413 Request Representation Too Large
The server is refusing to process a request because the request The server is refusing to process a request because the request
representation is larger than the server is willing or able to representation is larger than the server is willing or able to
process. The server MAY close the connection to prevent the client process. The server MAY close the connection to prevent the client
from continuing the request. from continuing the request.
If the condition is temporary, the server SHOULD include a Retry- If the condition is temporary, the server SHOULD include a Retry-
After header field to indicate that it is temporary and after what After header field to indicate that it is temporary and after what
time the client MAY try again. time the client MAY try again.
8.4.15. 414 URI Too Long 7.4.15. 414 URI Too Long
The server is refusing to service the request because the effective The server is refusing to service the request because the effective
request URI is longer than the server is willing to interpret. This request URI is longer than the server is willing to interpret. This
rare condition is only likely to occur when a client has improperly rare condition is only likely to occur when a client has improperly
converted a POST request to a GET request with long query converted a POST request to a GET request with long query
information, when the client has descended into a URI "black hole" of information, when the client has descended into a URI "black hole" of
redirection (e.g., a redirected URI prefix that points to a suffix of redirection (e.g., a redirected URI prefix that points to a suffix of
itself), or when the server is under attack by a client attempting to itself), or when the server is under attack by a client attempting to
exploit security holes present in some servers using fixed-length exploit security holes present in some servers using fixed-length
buffers for reading or manipulating the effective request URI. buffers for reading or manipulating the effective request URI.
8.4.16. 415 Unsupported Media Type 7.4.16. 415 Unsupported Media Type
The server is refusing to service the request because the request The server is refusing to service the request because the request
payload is in a format not supported by this request method on the payload is in a format not supported by this request method on the
target resource. target resource.
8.4.17. 416 Requested Range Not Satisfiable 7.4.17. 416 Requested Range Not Satisfiable
The request included a Range header field (Section 5.4 of [Part5]) The request included a Range header field (Section 5.4 of [Part5])
and none of the range-specifier values in this field overlap the and none of the range-specifier values in this field overlap the
current extent of the selected resource. See Section 3.2 of [Part5]. current extent of the selected resource. See Section 3.2 of [Part5].
8.4.18. 417 Expectation Failed 7.4.18. 417 Expectation Failed
The expectation given in an Expect header field (see Section 9.2) The expectation given in an Expect header field (see Section 9.3)
could not be met by this server, or, if the server is a proxy, the could not be met by this server, or, if the server is a proxy, the
server has unambiguous evidence that the request could not be met by server has unambiguous evidence that the request could not be met by
the next-hop server. the next-hop server.
8.4.19. 426 Upgrade Required 7.4.19. 426 Upgrade Required
The request can not be completed without a prior protocol upgrade. The request can not be completed without a prior protocol upgrade.
This response MUST include an Upgrade header field (Section 9.8 of This response MUST include an Upgrade header field (Section 8.7 of
[Part1]) specifying the required protocols. [Part1]) specifying the required protocols.
Example: Example:
HTTP/1.1 426 Upgrade Required HTTP/1.1 426 Upgrade Required
Upgrade: HTTP/2.0 Upgrade: HTTP/2.0
Connection: Upgrade Connection: Upgrade
The server SHOULD include a message body in the 426 response which The server SHOULD include a message body in the 426 response which
indicates in human readable form the reason for the error and indicates in human readable form the reason for the error and
describes any alternative courses which may be available to the user. describes any alternative courses which may be available to the user.
8.5. Server Error 5xx 7.5. Server Error 5xx
Response status codes beginning with the digit "5" indicate cases in Response status codes beginning with the digit "5" indicate cases in
which the server is aware that it has erred or is incapable of which the server is aware that it has erred or is incapable of
performing the request. Except when responding to a HEAD request, performing the request. Except when responding to a HEAD request,
the server SHOULD include a representation containing an explanation the server SHOULD include a representation containing an explanation
of the error situation, and whether it is a temporary or permanent of the error situation, and whether it is a temporary or permanent
condition. User agents SHOULD display any included representation to condition. User agents SHOULD display any included representation to
the user. These response codes are applicable to any request method. the user. These response codes are applicable to any request method.
8.5.1. 500 Internal Server Error 7.5.1. 500 Internal Server Error
The server encountered an unexpected condition which prevented it The server encountered an unexpected condition which prevented it
from fulfilling the request. from fulfilling the request.
8.5.2. 501 Not Implemented 7.5.2. 501 Not Implemented
The server does not support the functionality required to fulfill the The server does not support the functionality required to fulfill the
request. This is the appropriate response when the server does not request. This is the appropriate response when the server does not
recognize the request method and is not capable of supporting it for recognize the request method and is not capable of supporting it for
any resource. any resource.
8.5.3. 502 Bad Gateway 7.5.3. 502 Bad Gateway
The server, while acting as a gateway or proxy, received an invalid The server, while acting as a gateway or proxy, received an invalid
response from the upstream server it accessed in attempting to response from the upstream server it accessed in attempting to
fulfill the request. fulfill the request.
8.5.4. 503 Service Unavailable 7.5.4. 503 Service Unavailable
The server is currently unable or unwilling to handle the request due The server is currently unable or unwilling to handle the request due
to reasons such as temporary overloading, maintenance of the server, to reasons such as temporary overloading, maintenance of the server,
or rate limiting of the client. or rate limiting of the client.
The implication is that this is a temporary condition which will be The implication is that this is a temporary condition which will be
alleviated after some delay. If known, the length of the delay MAY alleviated after some delay. If known, the length of the delay MAY
be indicated in a Retry-After header field (Section 9.7). If no be indicated in a Retry-After header field (Section 9.8). If no
Retry-After is given, the client SHOULD handle the response as it Retry-After is given, the client SHOULD handle the response as it
would for a 500 response. would for a 500 response.
Note: The existence of the 503 status code does not imply that a Note: The existence of the 503 status code does not imply that a
server must use it when becoming overloaded. Some servers might server must use it when becoming overloaded. Some servers might
wish to simply refuse the connection. wish to simply refuse the connection.
8.5.5. 504 Gateway Timeout 7.5.5. 504 Gateway Timeout
The server, while acting as a gateway or proxy, did not receive a The server, while acting as a gateway or proxy, did not receive a
timely response from the upstream server specified by the URI (e.g., timely response from the upstream server specified by the URI (e.g.,
HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed HTTP, FTP, LDAP) or some other auxiliary server (e.g., DNS) it needed
to access in attempting to complete the request. to access in attempting to complete the request.
Note to implementors: some deployed proxies are known to return Note to implementors: some deployed proxies are known to return
400 or 500 when DNS lookups time out. 400 or 500 when DNS lookups time out.
8.5.6. 505 HTTP Version Not Supported 7.5.6. 505 HTTP Version Not Supported
The server does not support, or refuses to support, the protocol The server does not support, or refuses to support, the protocol
version that was used in the request message. The server is version that was used in the request message. The server is
indicating that it is unable or unwilling to complete the request indicating that it is unable or unwilling to complete the request
using the same major version as the client, as described in Section using the same major version as the client, as described in Section
2.6 of [Part1], other than with this error message. The response 2.6 of [Part1], other than with this error message. The response
SHOULD contain a representation describing why that version is not SHOULD contain a representation describing why that version is not
supported and what other protocols are supported by that server. supported and what other protocols are supported by that server.
8. Date/Time Formats
HTTP applications have historically allowed three different formats
for date/time stamps. However, the preferred format is a fixed-
length subset of that defined by [RFC1123]:
Sun, 06 Nov 1994 08:49:37 GMT ; RFC 1123
The other formats are described here only for compatibility with
obsolete implementations.
Sunday, 06-Nov-94 08:49:37 GMT ; obsolete RFC 850 format
Sun Nov 6 08:49:37 1994 ; ANSI C's asctime() format
HTTP/1.1 clients and servers that parse a date value MUST accept all
three formats (for compatibility with HTTP/1.0), though they MUST
only generate the RFC 1123 format for representing HTTP-date values
in header fields.
All HTTP date/time stamps MUST be represented in Greenwich Mean Time
(GMT), without exception. For the purposes of HTTP, GMT is exactly
equal to UTC (Coordinated Universal Time). This is indicated in the
first two formats by the inclusion of "GMT" as the three-letter
abbreviation for time zone, and MUST be assumed when reading the
asctime format. HTTP-date is case sensitive and MUST NOT include
additional whitespace beyond that specifically included as SP in the
grammar.
HTTP-date = rfc1123-date / obs-date
Preferred format:
rfc1123-date = day-name "," SP date1 SP time-of-day SP GMT
; fixed length subset of the format defined in
; Section 5.2.14 of [RFC1123]
day-name = %x4D.6F.6E ; "Mon", case-sensitive
/ %x54.75.65 ; "Tue", case-sensitive
/ %x57.65.64 ; "Wed", case-sensitive
/ %x54.68.75 ; "Thu", case-sensitive
/ %x46.72.69 ; "Fri", case-sensitive
/ %x53.61.74 ; "Sat", case-sensitive
/ %x53.75.6E ; "Sun", case-sensitive
date1 = day SP month SP year
; e.g., 02 Jun 1982
day = 2DIGIT
month = %x4A.61.6E ; "Jan", case-sensitive
/ %x46.65.62 ; "Feb", case-sensitive
/ %x4D.61.72 ; "Mar", case-sensitive
/ %x41.70.72 ; "Apr", case-sensitive
/ %x4D.61.79 ; "May", case-sensitive
/ %x4A.75.6E ; "Jun", case-sensitive
/ %x4A.75.6C ; "Jul", case-sensitive
/ %x41.75.67 ; "Aug", case-sensitive
/ %x53.65.70 ; "Sep", case-sensitive
/ %x4F.63.74 ; "Oct", case-sensitive
/ %x4E.6F.76 ; "Nov", case-sensitive
/ %x44.65.63 ; "Dec", case-sensitive
year = 4DIGIT
GMT = %x47.4D.54 ; "GMT", case-sensitive
time-of-day = hour ":" minute ":" second
; 00:00:00 - 23:59:59
hour = 2DIGIT
minute = 2DIGIT
second = 2DIGIT
The semantics of day-name, day, month, year, and time-of-day are the
same as those defined for the RFC 5322 constructs with the
corresponding name ([RFC5322], Section 3.3).
Obsolete formats:
obs-date = rfc850-date / asctime-date
rfc850-date = day-name-l "," SP date2 SP time-of-day SP GMT
date2 = day "-" month "-" 2DIGIT
; day-month-year (e.g., 02-Jun-82)
day-name-l = %x4D.6F.6E.64.61.79 ; "Monday", case-sensitive
/ %x54.75.65.73.64.61.79 ; "Tuesday", case-sensitive
/ %x57.65.64.6E.65.73.64.61.79 ; "Wednesday", case-sensitive
/ %x54.68.75.72.73.64.61.79 ; "Thursday", case-sensitive
/ %x46.72.69.64.61.79 ; "Friday", case-sensitive
/ %x53.61.74.75.72.64.61.79 ; "Saturday", case-sensitive
/ %x53.75.6E.64.61.79 ; "Sunday", case-sensitive
asctime-date = day-name SP date3 SP time-of-day SP year
date3 = month SP ( 2DIGIT / ( SP 1DIGIT ))
; month day (e.g., Jun 2)
Note: Recipients of date values are encouraged to be robust in
accepting date values that might have been sent by non-HTTP
applications, as is sometimes the case when retrieving or posting
messages via proxies/gateways to SMTP or NNTP.
Note: HTTP requirements for the date/time stamp format apply only
to their usage within the protocol stream. Clients and servers
are not required to use these formats for user presentation,
request logging, etc.
9. Header Field Definitions 9. Header Field Definitions
This section defines the syntax and semantics of HTTP/1.1 header This section defines the syntax and semantics of HTTP/1.1 header
fields related to request and response semantics. fields related to request and response semantics.
9.1. Allow 9.1. Allow
The "Allow" header field lists the set of methods advertised as The "Allow" header field lists the set of methods advertised as
supported by the target resource. The purpose of this field is supported by the target resource. The purpose of this field is
strictly to inform the recipient of valid request methods associated strictly to inform the recipient of valid request methods associated
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Allow: GET, HEAD, PUT Allow: GET, HEAD, PUT
The actual set of allowed methods is defined by the origin server at The actual set of allowed methods is defined by the origin server at
the time of each request. the time of each request.
A proxy MUST NOT modify the Allow header field -- it does not need to A proxy MUST NOT modify the Allow header field -- it does not need to
understand all the methods specified in order to handle them understand all the methods specified in order to handle them
according to the generic message handling rules. according to the generic message handling rules.
9.2. Expect 9.2. Date
The "Date" header field represents the date and time at which the
message was originated, having the same semantics as the Origination
Date Field (orig-date) defined in Section 3.6.1 of [RFC5322]. The
field value is an HTTP-date, as defined in Section 8; it MUST be sent
in rfc1123-date format.
Date = HTTP-date
An example is
Date: Tue, 15 Nov 1994 08:12:31 GMT
Origin servers MUST include a Date header field in all responses,
except in these cases:
1. If the response status code is 100 (Continue) or 101 (Switching
Protocols), the response MAY include a Date header field, at the
server's option.
2. If the response status code conveys a server error, e.g., 500
(Internal Server Error) or 503 (Service Unavailable), and it is
inconvenient or impossible to generate a valid Date.
3. If the server does not have a clock that can provide a reasonable
approximation of the current time, its responses MUST NOT include
a Date header field.
A received message that does not have a Date header field MUST be
assigned one by the recipient if the message will be cached by that
recipient.
Clients can use the Date header field as well; in order to keep
request messages small, they are advised not to include it when it
doesn't convey any useful information (as it is usually the case for
requests that do not contain a payload).
The HTTP-date sent in a Date header field SHOULD NOT represent a date
and time subsequent to the generation of the message. It SHOULD
represent the best available approximation of the date and time of
message generation, unless the implementation has no means of
generating a reasonably accurate date and time. In theory, the date
ought to represent the moment just before the payload is generated.
In practice, the date can be generated at any time during the message
origination without affecting its semantic value.
9.3. Expect
The "Expect" header field is used to indicate that particular server The "Expect" header field is used to indicate that particular server
behaviors are required by the client. behaviors are required by the client.
Expect = 1#expectation Expect = 1#expectation
expectation = "100-continue" / expectation-extension expectation = "100-continue" / expectation-extension
expectation-extension = token [ "=" ( token / quoted-string ) expectation-extension = token [ "=" ( token / quoted-string )
*expect-params ] *expect-params ]
expect-params = ";" token [ "=" ( token / quoted-string ) ] expect-params = ";" token [ "=" ( token / quoted-string ) ]
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The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy MUST The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy MUST
return a 417 (Expectation Failed) status code if it receives a return a 417 (Expectation Failed) status code if it receives a
request with an expectation that it cannot meet. However, the Expect request with an expectation that it cannot meet. However, the Expect
header field itself is end-to-end; it MUST be forwarded if the header field itself is end-to-end; it MUST be forwarded if the
request is forwarded. request is forwarded.
Many older HTTP/1.0 and HTTP/1.1 applications do not understand the Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
Expect header field. Expect header field.
See Section 7.2.3 of [Part1] for the use of the 100 (Continue) status See Section 6.2.3 of [Part1] for the use of the 100 (Continue) status
code. code.
9.3. From 9.4. From
The "From" header field, if given, SHOULD contain an Internet e-mail The "From" header field, if given, SHOULD contain an Internet e-mail
address for the human user who controls the requesting user agent. address for the human user who controls the requesting user agent.
The address SHOULD be machine-usable, as defined by "mailbox" in The address SHOULD be machine-usable, as defined by "mailbox" in
Section 3.4 of [RFC5322]: Section 3.4 of [RFC5322]:
From = mailbox From = mailbox
mailbox = <mailbox, defined in [RFC5322], Section 3.4> mailbox = <mailbox, defined in [RFC5322], Section 3.4>
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Internet host which issued the request. For example, when a request Internet host which issued the request. For example, when a request
is passed through a proxy the original issuer's address SHOULD be is passed through a proxy the original issuer's address SHOULD be
used. used.
The client SHOULD NOT send the From header field without the user's The client SHOULD NOT send the From header field without the user's
approval, as it might conflict with the user's privacy interests or approval, as it might conflict with the user's privacy interests or
their site's security policy. It is strongly recommended that the their site's security policy. It is strongly recommended that the
user be able to disable, enable, and modify the value of this field user be able to disable, enable, and modify the value of this field
at any time prior to a request. at any time prior to a request.
9.4. Location 9.5. Location
The "Location" header field is used to identify a newly created The "Location" header field is used to identify a newly created
resource, or to redirect the recipient to a different location for resource, or to redirect the recipient to a different location for
completion of the request. completion of the request.
For 201 (Created) responses, the Location is the URI of the new For 201 (Created) responses, the Location is the URI of the new
resource which was created by the request. For 3xx responses, the resource which was created by the request. For 3xx responses, the
location SHOULD indicate the server's preferred URI for automatic location SHOULD indicate the server's preferred URI for automatic
redirection to the resource. redirection to the resource.
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identifiers. Thus be aware that including fragment identifiers identifiers. Thus be aware that including fragment identifiers
might inconvenience anyone relying on the semantics of the might inconvenience anyone relying on the semantics of the
original URI's fragment identifier. original URI's fragment identifier.
Note: The Content-Location header field (Section 6.7 of [Part3]) Note: The Content-Location header field (Section 6.7 of [Part3])
differs from Location in that the Content-Location identifies the differs from Location in that the Content-Location identifies the
most specific resource corresponding to the enclosed most specific resource corresponding to the enclosed
representation. It is therefore possible for a response to representation. It is therefore possible for a response to
contain header fields for both Location and Content-Location. contain header fields for both Location and Content-Location.
9.5. Max-Forwards 9.6. Max-Forwards
The "Max-Forwards" header field provides a mechanism with the TRACE The "Max-Forwards" header field provides a mechanism with the TRACE
(Section 7.8) and OPTIONS (Section 7.2) methods to limit the number (Section 6.8) and OPTIONS (Section 6.2) methods to limit the number
of times that the request is forwarded by proxies. This can be of times that the request is forwarded by proxies. This can be
useful when the client is attempting to trace a request which appears useful when the client is attempting to trace a request which appears
to be failing or looping in mid-chain. to be failing or looping in mid-chain.
Max-Forwards = 1*DIGIT Max-Forwards = 1*DIGIT
The Max-Forwards value is a decimal integer indicating the remaining The Max-Forwards value is a decimal integer indicating the remaining
number of times this request message can be forwarded. number of times this request message can be forwarded.
Each recipient of a TRACE or OPTIONS request containing a Max- Each recipient of a TRACE or OPTIONS request containing a Max-
Forwards header field MUST check and update its value prior to Forwards header field MUST check and update its value prior to
forwarding the request. If the received value is zero (0), the forwarding the request. If the received value is zero (0), the
recipient MUST NOT forward the request; instead, it MUST respond as recipient MUST NOT forward the request; instead, it MUST respond as
the final recipient. If the received Max-Forwards value is greater the final recipient. If the received Max-Forwards value is greater
than zero, then the forwarded message MUST contain an updated Max- than zero, then the forwarded message MUST contain an updated Max-
Forwards field with a value decremented by one (1). Forwards field with a value decremented by one (1).
The Max-Forwards header field MAY be ignored for all other request The Max-Forwards header field MAY be ignored for all other request
methods. methods.
9.6. Referer 9.7. Referer
The "Referer" [sic] header field allows the client to specify the URI The "Referer" [sic] header field allows the client to specify the URI
of the resource from which the effective request URI was obtained of the resource from which the effective request URI was obtained
(the "referrer", although the header field is misspelled.). (the "referrer", although the header field is misspelled.).
The Referer header field allows servers to generate lists of back- The Referer header field allows servers to generate lists of back-
links to resources for interest, logging, optimized caching, etc. It links to resources for interest, logging, optimized caching, etc. It
also allows obsolete or mistyped links to be traced for maintenance. also allows obsolete or mistyped links to be traced for maintenance.
Some servers use Referer as a means of controlling where they allow Some servers use Referer as a means of controlling where they allow
links from (so-called "deep linking"), but legitimate requests do not links from (so-called "deep linking"), but legitimate requests do not
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Referer = absolute-URI / partial-URI Referer = absolute-URI / partial-URI
Example: Example:
Referer: http://www.example.org/hypertext/Overview.html Referer: http://www.example.org/hypertext/Overview.html
If the field value is a relative URI, it SHOULD be interpreted If the field value is a relative URI, it SHOULD be interpreted
relative to the effective request URI. The URI MUST NOT include a relative to the effective request URI. The URI MUST NOT include a
fragment. See Section 11.2 for security considerations. fragment. See Section 11.2 for security considerations.
9.7. Retry-After 9.8. Retry-After
The header "Retry-After" field can be used with a 503 (Service The header "Retry-After" field can be used with a 503 (Service
Unavailable) response to indicate how long the service is expected to Unavailable) response to indicate how long the service is expected to
be unavailable to the requesting client. This field MAY also be used be unavailable to the requesting client. This field MAY also be used
with any 3xx (Redirection) response to indicate the minimum time the with any 3xx (Redirection) response to indicate the minimum time the
user-agent is asked wait before issuing the redirected request. user-agent is asked wait before issuing the redirected request.
The value of this field can be either an HTTP-date or an integer The value of this field can be either an HTTP-date or an integer
number of seconds (in decimal) after the time of the response. number of seconds (in decimal) after the time of the response.
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number of seconds (in decimal) after the time of the response. number of seconds (in decimal) after the time of the response.
Retry-After = HTTP-date / delta-seconds Retry-After = HTTP-date / delta-seconds
Time spans are non-negative decimal integers, representing time in Time spans are non-negative decimal integers, representing time in
seconds. seconds.
delta-seconds = 1*DIGIT delta-seconds = 1*DIGIT
Two examples of its use are Two examples of its use are
Retry-After: Fri, 31 Dec 1999 23:59:59 GMT Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
Retry-After: 120 Retry-After: 120
In the latter example, the delay is 2 minutes. In the latter example, the delay is 2 minutes.
9.8. Server 9.9. Server
The "Server" header field contains information about the software The "Server" header field contains information about the software
used by the origin server to handle the request. used by the origin server to handle the request.
The field can contain multiple product tokens (Section 6.3 of The field can contain multiple product tokens (Section 5.2 of
[Part1]) and comments (Section 3.2 of [Part1]) identifying the server [Part1]) and comments (Section 3.2 of [Part1]) identifying the server
and any significant subproducts. The product tokens are listed in and any significant subproducts. The product tokens are listed in
order of their significance for identifying the application. order of their significance for identifying the application.
Server = product *( RWS ( product / comment ) ) Server = product *( RWS ( product / comment ) )
Example: Example:
Server: CERN/3.0 libwww/2.17 Server: CERN/3.0 libwww/2.17
If the response is being forwarded through a proxy, the proxy If the response is being forwarded through a proxy, the proxy
application MUST NOT modify the Server header field. Instead, it application MUST NOT modify the Server header field. Instead, it
MUST include a Via field (as described in Section 9.9 of [Part1]). MUST include a Via field (as described in Section 8.8 of [Part1]).
Note: Revealing the specific software version of the server might Note: Revealing the specific software version of the server might
allow the server machine to become more vulnerable to attacks allow the server machine to become more vulnerable to attacks
against software that is known to contain security holes. Server against software that is known to contain security holes. Server
implementors are encouraged to make this field a configurable implementors are encouraged to make this field a configurable
option. option.
9.9. User-Agent 9.10. User-Agent
The "User-Agent" header field contains information about the user The "User-Agent" header field contains information about the user
agent originating the request. User agents SHOULD include this field agent originating the request. User agents SHOULD include this field
with requests. with requests.
Typically, it is used for statistical purposes, the tracing of Typically, it is used for statistical purposes, the tracing of
protocol violations, and tailoring responses to avoid particular user protocol violations, and tailoring responses to avoid particular user
agent limitations. agent limitations.
The field can contain multiple product tokens (Section 6.3 of The field can contain multiple product tokens (Section 5.2 of
[Part1]) and comments (Section 3.2 of [Part1]) identifying the agent [Part1]) and comments (Section 3.2 of [Part1]) identifying the agent
and its significant subproducts. By convention, the product tokens and its significant subproducts. By convention, the product tokens
are listed in order of their significance for identifying the are listed in order of their significance for identifying the
application. application.
Because this field is usually sent on every request a user agent Because this field is usually sent on every request a user agent
makes, implementations are encouraged not to include needlessly fine- makes, implementations are encouraged not to include needlessly fine-
grained detail, and to limit (or even prohibit) the addition of grained detail, and to limit (or even prohibit) the addition of
subproducts by third parties. Overly long and detailed User-Agent subproducts by third parties. Overly long and detailed User-Agent
field values make requests larger and can also be used to identify field values make requests larger and can also be used to identify
skipping to change at page 42, line 21 skipping to change at page 49, line 36
The registration procedure for HTTP request methods is defined by The registration procedure for HTTP request methods is defined by
Section 2.2 of this document. Section 2.2 of this document.
The HTTP Method Registry shall be created at The HTTP Method Registry shall be created at
<http://www.iana.org/assignments/http-methods> and be populated with <http://www.iana.org/assignments/http-methods> and be populated with
the registrations below: the registrations below:
+---------+------+-------------+ +---------+------+-------------+
| Method | Safe | Reference | | Method | Safe | Reference |
+---------+------+-------------+ +---------+------+-------------+
| CONNECT | no | Section 7.9 | | CONNECT | no | Section 6.9 |
| DELETE | no | Section 7.7 | | DELETE | no | Section 6.7 |
| GET | yes | Section 7.3 | | GET | yes | Section 6.3 |
| HEAD | yes | Section 7.4 | | HEAD | yes | Section 6.4 |
| OPTIONS | yes | Section 7.2 | | OPTIONS | yes | Section 6.2 |
| POST | no | Section 7.5 | | POST | no | Section 6.5 |
| PUT | no | Section 7.6 | | PUT | no | Section 6.6 |
| TRACE | yes | Section 7.8 | | TRACE | yes | Section 6.8 |
+---------+------+-------------+ +---------+------+-------------+
10.2. Status Code Registry 10.2. Status Code Registry
The registration procedure for HTTP Status Codes -- previously The registration procedure for HTTP Status Codes -- previously
defined in Section 7.1 of [RFC2817] -- is now defined by Section 4.2 defined in Section 7.1 of [RFC2817] -- is now defined by Section 4.2
of this document. of this document.
The HTTP Status Code Registry located at The HTTP Status Code Registry located at
<http://www.iana.org/assignments/http-status-codes> shall be updated <http://www.iana.org/assignments/http-status-codes> shall be updated
with the registrations below: with the registrations below:
+-------+----------------------------------+----------------+ +-------+----------------------------------+----------------+
| Value | Description | Reference | | Value | Description | Reference |
+-------+----------------------------------+----------------+ +-------+----------------------------------+----------------+
| 100 | Continue | Section 8.1.1 | | 100 | Continue | Section 7.1.1 |
| 101 | Switching Protocols | Section 8.1.2 | | 101 | Switching Protocols | Section 7.1.2 |
| 200 | OK | Section 8.2.1 | | 200 | OK | Section 7.2.1 |
| 201 | Created | Section 8.2.2 | | 201 | Created | Section 7.2.2 |
| 202 | Accepted | Section 8.2.3 | | 202 | Accepted | Section 7.2.3 |
| 203 | Non-Authoritative Information | Section 8.2.4 | | 203 | Non-Authoritative Information | Section 7.2.4 |
| 204 | No Content | Section 8.2.5 | | 204 | No Content | Section 7.2.5 |
| 205 | Reset Content | Section 8.2.6 | | 205 | Reset Content | Section 7.2.6 |
| 300 | Multiple Choices | Section 8.3.1 | | 300 | Multiple Choices | Section 7.3.1 |
| 301 | Moved Permanently | Section 8.3.2 | | 301 | Moved Permanently | Section 7.3.2 |
| 302 | Found | Section 8.3.3 | | 302 | Found | Section 7.3.3 |
| 303 | See Other | Section 8.3.4 | | 303 | See Other | Section 7.3.4 |
| 305 | Use Proxy | Section 8.3.6 | | 305 | Use Proxy | Section 7.3.6 |
| 306 | (Unused) | Section 8.3.7 | | 306 | (Unused) | Section 7.3.7 |
| 307 | Temporary Redirect | Section 8.3.8 | | 307 | Temporary Redirect | Section 7.3.8 |
| 400 | Bad Request | Section 8.4.1 | | 400 | Bad Request | Section 7.4.1 |
| 402 | Payment Required | Section 8.4.3 | | 402 | Payment Required | Section 7.4.3 |
| 403 | Forbidden | Section 8.4.4 | | 403 | Forbidden | Section 7.4.4 |
| 404 | Not Found | Section 8.4.5 | | 404 | Not Found | Section 7.4.5 |
| 405 | Method Not Allowed | Section 8.4.6 | | 405 | Method Not Allowed | Section 7.4.6 |
| 406 | Not Acceptable | Section 8.4.7 | | 406 | Not Acceptable | Section 7.4.7 |
| 407 | Proxy Authentication Required | Section 8.4.8 | | 407 | Proxy Authentication Required | Section 7.4.8 |
| 408 | Request Timeout | Section 8.4.9 | | 408 | Request Timeout | Section 7.4.9 |
| 409 | Conflict | Section 8.4.10 | | 409 | Conflict | Section 7.4.10 |
| 410 | Gone | Section 8.4.11 | | 410 | Gone | Section 7.4.11 |
| 411 | Length Required | Section 8.4.12 | | 411 | Length Required | Section 7.4.12 |
| 413 | Request Representation Too Large | Section 8.4.14 | | 413 | Request Representation Too Large | Section 7.4.14 |
| 414 | URI Too Long | Section 8.4.15 | | 414 | URI Too Long | Section 7.4.15 |
| 415 | Unsupported Media Type | Section 8.4.16 | | 415 | Unsupported Media Type | Section 7.4.16 |
| 417 | Expectation Failed | Section 8.4.18 | | 417 | Expectation Failed | Section 7.4.18 |
| 426 | Upgrade Required | Section 8.4.19 | | 426 | Upgrade Required | Section 7.4.19 |
| 500 | Internal Server Error | Section 8.5.1 | | 500 | Internal Server Error | Section 7.5.1 |
| 501 | Not Implemented | Section 8.5.2 | | 501 | Not Implemented | Section 7.5.2 |
| 502 | Bad Gateway | Section 8.5.3 | | 502 | Bad Gateway | Section 7.5.3 |
| 503 | Service Unavailable | Section 8.5.4 | | 503 | Service Unavailable | Section 7.5.4 |
| 504 | Gateway Timeout | Section 8.5.5 | | 504 | Gateway Timeout | Section 7.5.5 |
| 505 | HTTP Version Not Supported | Section 8.5.6 | | 505 | HTTP Version Not Supported | Section 7.5.6 |
+-------+----------------------------------+----------------+ +-------+----------------------------------+----------------+
10.3. Header Field Registration 10.3. Header Field Registration
The Message Header Field Registry located at <http://www.iana.org/ The Message Header Field Registry located at <http://www.iana.org/
assignments/message-headers/message-header-index.html> shall be assignments/message-headers/message-header-index.html> shall be
updated with the permanent registrations below (see [RFC3864]): updated with the permanent registrations below (see [RFC3864]):
+-------------------+----------+----------+-------------+ +-------------------+----------+----------+--------------+
| Header Field Name | Protocol | Status | Reference | | Header Field Name | Protocol | Status | Reference |
+-------------------+----------+----------+-------------+ +-------------------+----------+----------+--------------+
| Allow | http | standard | Section 9.1 | | Allow | http | standard | Section 9.1 |
| Expect | http | standard | Section 9.2 | | Date | http | standard | Section 9.2 |
| From | http | standard | Section 9.3 | | Expect | http | standard | Section 9.3 |
| Location | http | standard | Section 9.4 | | From | http | standard | Section 9.4 |
| Max-Forwards | http | standard | Section 9.5 | | Location | http | standard | Section 9.5 |
| Referer | http | standard | Section 9.6 | | Max-Forwards | http | standard | Section 9.6 |
| Retry-After | http | standard | Section 9.7 | | Referer | http | standard | Section 9.7 |
| Server | http | standard | Section 9.8 | | Retry-After | http | standard | Section 9.8 |
| User-Agent | http | standard | Section 9.9 | | Server | http | standard | Section 9.9 |
+-------------------+----------+----------+-------------+ | User-Agent | http | standard | Section 9.10 |
+-------------------+----------+----------+--------------+
The change controller is: "IETF (iesg@ietf.org) - Internet The change controller is: "IETF (iesg@ietf.org) - Internet
Engineering Task Force". Engineering Task Force".
11. Security Considerations 11. Security Considerations
This section is meant to inform application developers, information This section is meant to inform application developers, information
providers, and users of the security limitations in HTTP/1.1 as providers, and users of the security limitations in HTTP/1.1 as
described by this document. The discussion does not include described by this document. The discussion does not include
definitive solutions to the problems revealed, though it does make definitive solutions to the problems revealed, though it does make
skipping to change at page 45, line 20 skipping to change at page 52, line 27
privacy interests or their site's security policy, and hence it privacy interests or their site's security policy, and hence it
SHOULD NOT be transmitted without the user being able to disable, SHOULD NOT be transmitted without the user being able to disable,
enable, and modify the contents of the field. The user MUST be able enable, and modify the contents of the field. The user MUST be able
to set the contents of this field within a user preference or to set the contents of this field within a user preference or
application defaults configuration. application defaults configuration.
We suggest, though do not require, that a convenient toggle interface We suggest, though do not require, that a convenient toggle interface
be provided for the user to enable or disable the sending of From and be provided for the user to enable or disable the sending of From and
Referer information. Referer information.
The User-Agent (Section 9.9) or Server (Section 9.8) header fields The User-Agent (Section 9.10) or Server (Section 9.9) header fields
can sometimes be used to determine that a specific client or server can sometimes be used to determine that a specific client or server
have a particular security hole which might be exploited. have a particular security hole which might be exploited.
Unfortunately, this same information is often used for other valuable Unfortunately, this same information is often used for other valuable
purposes for which HTTP currently has no better mechanism. purposes for which HTTP currently has no better mechanism.
Furthermore, the User-Agent header field may contain enough entropy Furthermore, the User-Agent header field may contain enough entropy
to be used, possibly in conjunction with other material, to uniquely to be used, possibly in conjunction with other material, to uniquely
identify the user. identify the user.
Some request methods, like TRACE (Section 7.8), expose information Some request methods, like TRACE (Section 6.8), expose information
that was sent in request header fields within the body of their that was sent in request header fields within the body of their
response. Clients SHOULD be careful with sensitive information, like response. Clients SHOULD be careful with sensitive information, like
Cookies, Authorization credentials, and other header fields that Cookies, Authorization credentials, and other header fields that
might be used to collect data from the client. might be used to collect data from the client.
11.2. Encoding Sensitive Information in URIs 11.2. Encoding Sensitive Information in URIs
Because the source of a link might be private information or might Because the source of a link might be private information or might
reveal an otherwise private information source, it is strongly reveal an otherwise private information source, it is strongly
recommended that the user be able to select whether or not the recommended that the user be able to select whether or not the
skipping to change at page 46, line 27 skipping to change at page 53, line 34
11.4. Security Considerations for CONNECT 11.4. Security Considerations for CONNECT
Since tunneled data is opaque to the proxy, there are additional Since tunneled data is opaque to the proxy, there are additional
risks to tunneling to other well-known or reserved ports. A HTTP risks to tunneling to other well-known or reserved ports. A HTTP
client CONNECTing to port 25 could relay spam via SMTP, for example. client CONNECTing to port 25 could relay spam via SMTP, for example.
As such, proxies SHOULD restrict CONNECT access to a small number of As such, proxies SHOULD restrict CONNECT access to a small number of
known ports. known ports.
12. Acknowledgments 12. Acknowledgments
See Section 12 of [Part1]. See Section 11 of [Part1].
13. References 13. References
13.1. Normative References 13.1. Normative References
[Part1] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part1] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 1: URIs, Connections, and J. Reschke, Ed., "HTTP/1.1, part 1: URIs, Connections,
and Message Parsing", draft-ietf-httpbis-p1-messaging-16 and Message Parsing", draft-ietf-httpbis-p1-messaging-17
(work in progress), August 2011. (work in progress), October 2011.
[Part3] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part3] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 3: Message Payload and J. Reschke, Ed., "HTTP/1.1, part 3: Message Payload
and Content Negotiation", draft-ietf-httpbis-p3-payload-16 and Content Negotiation", draft-ietf-httpbis-p3-payload-17
(work in progress), August 2011. (work in progress), October 2011.
[Part4] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part4] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 4: Conditional and J. Reschke, Ed., "HTTP/1.1, part 4: Conditional
Requests", draft-ietf-httpbis-p4-conditional-16 (work in Requests", draft-ietf-httpbis-p4-conditional-17 (work in
progress), August 2011. progress), October 2011.
[Part5] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part5] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 5: Range Requests and and J. Reschke, Ed., "HTTP/1.1, part 5: Range Requests and
Partial Responses", draft-ietf-httpbis-p5-range-16 (work Partial Responses", draft-ietf-httpbis-p5-range-17 (work
in progress), August 2011. in progress), October 2011.
[Part6] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part6] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
Nottingham, M., Ed., and J. Reschke, Ed., "HTTP/1.1, part Nottingham, M., Ed., and J. Reschke, Ed., "HTTP/1.1, part
6: Caching", draft-ietf-httpbis-p6-cache-16 (work in 6: Caching", draft-ietf-httpbis-p6-cache-17 (work in
progress), August 2011. progress), October 2011.
[Part7] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H., [Part7] Fielding, R., Ed., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed., Masinter, L., Leach, P., Berners-Lee, T., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 7: Authentication", and J. Reschke, Ed., "HTTP/1.1, part 7: Authentication",
draft-ietf-httpbis-p7-auth-16 (work in progress), draft-ietf-httpbis-p7-auth-17 (work in progress),
August 2011. October 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005. RFC 3986, January 2005.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
13.2. Informative References 13.2. Informative References
[RFC1123] Braden, R., "Requirements for Internet Hosts - Application
and Support", STD 3, RFC 1123, October 1989.
[RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen, "Hypertext [RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen, "Hypertext
Transfer Protocol -- HTTP/1.0", RFC 1945, May 1996. Transfer Protocol -- HTTP/1.0", RFC 1945, May 1996.
[RFC2068] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and T. [RFC2068] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and T.
Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1",
RFC 2068, January 1997. RFC 2068, January 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
skipping to change at page 48, line 13 skipping to change at page 55, line 22
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008. May 2008.
[RFC5322] Resnick, P., "Internet Message Format", RFC 5322, [RFC5322] Resnick, P., "Internet Message Format", RFC 5322,
October 2008. October 2008.
[RFC5789] Dusseault, L. and J. Snell, "PATCH Method for HTTP", [RFC5789] Dusseault, L. and J. Snell, "PATCH Method for HTTP",
RFC 5789, March 2010. RFC 5789, March 2010.
[RFC5987] Reschke, J., "Character Set and Language Encoding for
Hypertext Transfer Protocol (HTTP) Header Field
Parameters", RFC 5987, August 2010.
Appendix A. Changes from RFC 2616 Appendix A. Changes from RFC 2616
This document takes over the Status Code Registry, previously defined This document takes over the Status Code Registry, previously defined
in Section 7.1 of [RFC2817]. (Section 4.2) in Section 7.1 of [RFC2817]. (Section 4.2)
Clarify definition of POST. (Section 7.5) Clarify definition of POST. (Section 6.5)
Remove requirement to handle all Content-* header fields; ban use of Remove requirement to handle all Content-* header fields; ban use of
Content-Range with PUT. (Section 7.6) Content-Range with PUT. (Section 6.6)
Take over definition of CONNECT method from [RFC2817]. (Section 7.9) Take over definition of CONNECT method from [RFC2817]. (Section 6.9)
Broadened the definition of 203 (Non-Authoritative Information) to Broadened the definition of 203 (Non-Authoritative Information) to
include cases of payload transformations as well. (Section 8.2.4) include cases of payload transformations as well. (Section 7.2.4)
Failed to consider that there are many other request methods that are Failed to consider that there are many other request methods that are
safe to automatically redirect, and further that the user agent is safe to automatically redirect, and further that the user agent is
able to make that determination based on the request method able to make that determination based on the request method
semantics. (Sections 8.3.2, 8.3.3 and 8.3.8) semantics. Furthermore, allow user agents to rewrite the method from
POST to GET for status codes 301 and 302. (Sections 7.3.2, 7.3.3 and
7.3.8)
Deprecate 305 Use Proxy status code, because user agents did not Deprecate 305 Use Proxy status code, because user agents did not
implement it. It used to indicate that the target resource must be implement it. It used to indicate that the target resource must be
accessed through the proxy given by the Location field. The Location accessed through the proxy given by the Location field. The Location
field gave the URI of the proxy. The recipient was expected to field gave the URI of the proxy. The recipient was expected to
repeat this single request via the proxy. (Section 8.3.6) repeat this single request via the proxy. (Section 7.3.6)
Define status 426 (Upgrade Required) (this was incorporated from Define status 426 (Upgrade Required) (this was incorporated from
[RFC2817]). (Section 8.4.19) [RFC2817]). (Section 7.4.19)
Change ABNF productions for header fields to only define the field Change ABNF productions for header fields to only define the field
value. (Section 9) value. (Section 9)
Reclassify "Allow" as response header field, removing the option to Reclassify "Allow" as response header field, removing the option to
specify it in a PUT request. Relax the server requirement on the specify it in a PUT request. Relax the server requirement on the
contents of the Allow header field and remove requirement on clients contents of the Allow header field and remove requirement on clients
to always trust the header field value. (Section 9.1) to always trust the header field value. (Section 9.1)
Correct syntax of Location header field to allow URI references Correct syntax of Location header field to allow URI references
(including relative references and fragments), as referred symbol (including relative references and fragments), as referred symbol
"absoluteURI" wasn't what was expected, and add some clarifications "absoluteURI" wasn't what was expected, and add some clarifications
as to when use of fragments would not be appropriate. (Section 9.4) as to when use of fragments would not be appropriate. (Section 9.5)
Restrict Max-Forwards header field to OPTIONS and TRACE (previously, Restrict Max-Forwards header field to OPTIONS and TRACE (previously,
extension methods could have used it as well). (Section 9.5) extension methods could have used it as well). (Section 9.6)
Allow Referer field value of "about:blank" as alternative to not Allow Referer field value of "about:blank" as alternative to not
specifying it. (Section 9.6) specifying it. (Section 9.7)
In the description of the Server header field, the Via field was In the description of the Server header field, the Via field was
described as a SHOULD. The requirement was and is stated correctly described as a SHOULD. The requirement was and is stated correctly
in the description of the Via header field in Section 9.9 of [Part1]. in the description of the Via header field in Section 8.8 of [Part1].
(Section 9.8) (Section 9.9)
Appendix B. Collected ABNF Appendix B. Collected ABNF
Allow = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ] Allow = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]
Date = HTTP-date
Expect = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] ) Expect = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
From = mailbox From = mailbox
HTTP-date = <HTTP-date, defined in [Part1], Section 6.1> GMT = %x47.4D.54 ; GMT
HTTP-date = rfc1123-date / obs-date
Location = URI-reference Location = URI-reference
Max-Forwards = 1*DIGIT Max-Forwards = 1*DIGIT
Method = token Method = token
OWS = <OWS, defined in [Part1], Section 1.2.2> OWS = <OWS, defined in [Part1], Section 1.2.2>
RWS = <RWS, defined in [Part1], Section 1.2.2> RWS = <RWS, defined in [Part1], Section 1.2.2>
Reason-Phrase = *( WSP / VCHAR / obs-text ) Reason-Phrase = *( HTAB / SP / VCHAR / obs-text )
Referer = absolute-URI / partial-URI Referer = absolute-URI / partial-URI
Retry-After = HTTP-date / delta-seconds Retry-After = HTTP-date / delta-seconds
Server = product *( RWS ( product / comment ) ) Server = product *( RWS ( product / comment ) )
Status-Code = 3DIGIT Status-Code = 3DIGIT
URI-reference = <URI-reference, defined in [Part1], Section 2.7> URI-reference = <URI-reference, defined in [Part1], Section 2.7>
User-Agent = product *( RWS ( product / comment ) ) User-Agent = product *( RWS ( product / comment ) )
absolute-URI = <absolute-URI, defined in [Part1], Section 2.7> absolute-URI = <absolute-URI, defined in [Part1], Section 2.7>
asctime-date = day-name SP date3 SP time-of-day SP year
comment = <comment, defined in [Part1], Section 3.2> comment = <comment, defined in [Part1], Section 3.2>
date1 = day SP month SP year
date2 = day "-" month "-" 2DIGIT
date3 = month SP ( 2DIGIT / ( SP DIGIT ) )
day = 2DIGIT
day-name = %x4D.6F.6E ; Mon
/ %x54.75.65 ; Tue
/ %x57.65.64 ; Wed
/ %x54.68.75 ; Thu
/ %x46.72.69 ; Fri
/ %x53.61.74 ; Sat
/ %x53.75.6E ; Sun
day-name-l = %x4D.6F.6E.64.61.79 ; Monday
/ %x54.75.65.73.64.61.79 ; Tuesday
/ %x57.65.64.6E.65.73.64.61.79 ; Wednesday
/ %x54.68.75.72.73.64.61.79 ; Thursday
/ %x46.72.69.64.61.79 ; Friday
/ %x53.61.74.75.72.64.61.79 ; Saturday
/ %x53.75.6E.64.61.79 ; Sunday
delta-seconds = 1*DIGIT delta-seconds = 1*DIGIT
expect-params = ";" token [ "=" ( token / quoted-string ) ] expect-params = ";" token [ "=" ( token / quoted-string ) ]
expectation = "100-continue" / expectation-extension expectation = "100-continue" / expectation-extension
expectation-extension = token [ "=" ( token / quoted-string ) expectation-extension = token [ "=" ( token / quoted-string )
*expect-params ] *expect-params ]
hour = 2DIGIT
mailbox = <mailbox, defined in [RFC5322], Section 3.4> mailbox = <mailbox, defined in [RFC5322], Section 3.4>
minute = 2DIGIT
month = %x4A.61.6E ; Jan
/ %x46.65.62 ; Feb
/ %x4D.61.72 ; Mar
/ %x41.70.72 ; Apr
/ %x4D.61.79 ; May
/ %x4A.75.6E ; Jun
/ %x4A.75.6C ; Jul
/ %x41.75.67 ; Aug
/ %x53.65.70 ; Sep
/ %x4F.63.74 ; Oct
/ %x4E.6F.76 ; Nov
/ %x44.65.63 ; Dec
obs-date = rfc850-date / asctime-date
obs-text = <obs-text, defined in [Part1], Section 1.2.2> obs-text = <obs-text, defined in [Part1], Section 1.2.2>
partial-URI = <partial-URI, defined in [Part1], Section 2.7> partial-URI = <partial-URI, defined in [Part1], Section 2.7>
product = <product, defined in [Part1], Section 6.3> product = <product, defined in [Part1], Section 5.2>
quoted-string = <quoted-string, defined in [Part1], Section 3.2.3> quoted-string = <quoted-string, defined in [Part1], Section 3.2.3>
rfc1123-date = day-name "," SP date1 SP time-of-day SP GMT
rfc850-date = day-name-l "," SP date2 SP time-of-day SP GMT
second = 2DIGIT
time-of-day = hour ":" minute ":" second
token = <token, defined in [Part1], Section 3.2.3> token = <token, defined in [Part1], Section 3.2.3>
year = 4DIGIT
ABNF diagnostics: ABNF diagnostics:
; Allow defined but not used ; Allow defined but not used
; Date defined but not used
; Expect defined but not used ; Expect defined but not used
; From defined but not used ; From defined but not used
; Location defined but not used ; Location defined but not used
; Max-Forwards defined but not used ; Max-Forwards defined but not used
; Reason-Phrase defined but not used ; Reason-Phrase defined but not used
; Referer defined but not used ; Referer defined but not used
; Retry-After defined but not used ; Retry-After defined but not used
; Server defined but not used ; Server defined but not used
; Status-Code defined but not used ; Status-Code defined but not used
; User-Agent defined but not used ; User-Agent defined but not used
skipping to change at page 58, line 41 skipping to change at page 66, line 31
C.17. Since draft-ietf-httpbis-p2-semantics-15 C.17. Since draft-ietf-httpbis-p2-semantics-15
Closed issues: Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/285>: "Strength of o <http://tools.ietf.org/wg/httpbis/trac/ticket/285>: "Strength of
requirements on Accept re: 406" requirements on Accept re: 406"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/303>: "400 response o <http://tools.ietf.org/wg/httpbis/trac/ticket/303>: "400 response
isn't generic" isn't generic"
C.18. Since draft-ietf-httpbis-p2-semantics-16
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/160>: "Redirects and
non-GET methods"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/186>: "Document
HTTP's error-handling philosophy"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/231>:
"Considerations for new headers"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/310>: "clarify 303
redirect on HEAD"
Index Index
1 1
100 Continue (status code) 23 100 Continue (status code) 26
101 Switching Protocols (status code) 23 101 Switching Protocols (status code) 26
2 2
200 OK (status code) 24 200 OK (status code) 27
201 Created (status code) 24 201 Created (status code) 27
202 Accepted (status code) 25 202 Accepted (status code) 28
203 Non-Authoritative Information (status code) 25 203 Non-Authoritative Information (status code) 28
204 No Content (status code) 25 204 No Content (status code) 28
205 Reset Content (status code) 26 205 Reset Content (status code) 29
206 Partial Content (status code) 26 206 Partial Content (status code) 29
3 3
300 Multiple Choices (status code) 27 300 Multiple Choices (status code) 30
301 Moved Permanently (status code) 27 301 Moved Permanently (status code) 31
302 Found (status code) 28 302 Found (status code) 32
303 See Other (status code) 28 303 See Other (status code) 32
304 Not Modified (status code) 29 304 Not Modified (status code) 33
305 Use Proxy (status code) 29 305 Use Proxy (status code) 33
306 (Unused) (status code) 29 306 (Unused) (status code) 33
307 Temporary Redirect (status code) 29 307 Temporary Redirect (status code) 33
4 4
400 Bad Request (status code) 30 400 Bad Request (status code) 34
401 Unauthorized (status code) 30 401 Unauthorized (status code) 34
402 Payment Required (status code) 30 402 Payment Required (status code) 34
403 Forbidden (status code) 30 403 Forbidden (status code) 34
404 Not Found (status code) 31 404 Not Found (status code) 35
405 Method Not Allowed (status code) 31 405 Method Not Allowed (status code) 35
406 Not Acceptable (status code) 31 406 Not Acceptable (status code) 35
407 Proxy Authentication Required (status code) 32 407 Proxy Authentication Required (status code) 35
408 Request Timeout (status code) 32 408 Request Timeout (status code) 36
409 Conflict (status code) 32 409 Conflict (status code) 36
410 Gone (status code) 32 410 Gone (status code) 36
411 Length Required (status code) 33 411 Length Required (status code) 37
412 Precondition Failed (status code) 33 412 Precondition Failed (status code) 37
413 Request Representation Too Large (status code) 33 413 Request Representation Too Large (status code) 37
414 URI Too Long (status code) 33 414 URI Too Long (status code) 37
415 Unsupported Media Type (status code) 34 415 Unsupported Media Type (status code) 37
416 Requested Range Not Satisfiable (status code) 34 416 Requested Range Not Satisfiable (status code) 38
417 Expectation Failed (status code) 34 417 Expectation Failed (status code) 38
426 Upgrade Required (status code) 34 426 Upgrade Required (status code) 38
5 5
500 Internal Server Error (status code) 35 500 Internal Server Error (status code) 38
501 Not Implemented (status code) 35 501 Not Implemented (status code) 39
502 Bad Gateway (status code) 35 502 Bad Gateway (status code) 39
503 Service Unavailable (status code) 35 503 Service Unavailable (status code) 39
504 Gateway Timeout (status code) 35 504 Gateway Timeout (status code) 39
505 HTTP Version Not Supported (status code) 36 505 HTTP Version Not Supported (status code) 39
A A
Allow header field 36 Allow header field 42
C C
CONNECT method 21 CONNECT method 24
D D
DELETE method 20 Date header field 43
DELETE method 23
E E
Expect header field 36 Expect header field 44
F F
From header field 37 From header field 44
G G
GET method 16 GET method 19
Grammar Grammar
Allow 36 Allow 42
delta-seconds 40 asctime-date 42
Expect 36 Date 43
expect-params 36 date1 41
expectation 36 day 41
expectation-extension 36 day-name 41
extension-code 10 day-name-l 41
From 37 delta-seconds 47
Location 38 Expect 44
Max-Forwards 39 expect-params 44
expectation 44
expectation-extension 44
extension-code 12
From 45
GMT 41
hour 41
HTTP-date 40
Location 45
Max-Forwards 46
Method 7 Method 7
Reason-Phrase 10 minute 41
Referer 40 month 41
Retry-After 40 obs-date 41
Server 40 Reason-Phrase 12
Status-Code 10 Referer 47
User-Agent 41 Retry-After 47
rfc850-date 42
rfc1123-date 41
second 41
Server 48
Status-Code 12
time-of-day 41
User-Agent 49
year 41
H H
HEAD method 17 HEAD method 19
Header Fields Header Fields
Allow 36 Allow 42
Expect 36 Date 43
From 37 Expect 44
Location 38 From 44
Max-Forwards 39 Location 45
Referer 39 Max-Forwards 46
Retry-After 40 Referer 47
Server 40 Retry-After 47
User-Agent 41 Server 48
User-Agent 48
I I
Idempotent Methods 15 Idempotent Methods 17
L L
Location header field 38 Location header field 45
M M
Max-Forwards header field 39 Max-Forwards header field 46
Methods Methods
CONNECT 21 CONNECT 24
DELETE 20 DELETE 23
GET 16 GET 19
HEAD 17 HEAD 19
OPTIONS 15 OPTIONS 18
POST 17 POST 20
PUT 18 PUT 21
TRACE 21 TRACE 23
O O
OPTIONS method 15 OPTIONS method 18
P P
POST method 17 POST method 20
PUT method 18 PUT method 21
R R
Referer header field 39 Referer header field 47
Retry-After header field 40 Retry-After header field 47
S S
Safe Methods 14 Safe Methods 17
Server header field 40 Server header field 48
Status Codes Status Codes
100 Continue 23 100 Continue 26
101 Switching Protocols 23 101 Switching Protocols 26
200 OK 24 200 OK 27
201 Created 24 201 Created 27
202 Accepted 25 202 Accepted 28
203 Non-Authoritative Information 25 203 Non-Authoritative Information 28
204 No Content 25 204 No Content 28
205 Reset Content 26 205 Reset Content 29
206 Partial Content 26 206 Partial Content 29
300 Multiple Choices 27 300 Multiple Choices 30
301 Moved Permanently 27 301 Moved Permanently 31
302 Found 28 302 Found 32
303 See Other 28 303 See Other 32
304 Not Modified 29 304 Not Modified 33
305 Use Proxy 29 305 Use Proxy 33
306 (Unused) 29 306 (Unused) 33
307 Temporary Redirect 29 307 Temporary Redirect 33
400 Bad Request 30 400 Bad Request 34
401 Unauthorized 30 401 Unauthorized 34
402 Payment Required 30 402 Payment Required 34
403 Forbidden 30 403 Forbidden 34
404 Not Found 31 404 Not Found 35
405 Method Not Allowed 31 405 Method Not Allowed 35
406 Not Acceptable 31 406 Not Acceptable 35
407 Proxy Authentication Required 32 407 Proxy Authentication Required 35
408 Request Timeout 32 408 Request Timeout 36
409 Conflict 32 409 Conflict 36
410 Gone 32 410 Gone 36
411 Length Required 33 411 Length Required 37
412 Precondition Failed 33 412 Precondition Failed 37
413 Request Representation Too Large 33 413 Request Representation Too Large 37
414 URI Too Long 33 414 URI Too Long 37
415 Unsupported Media Type 34 415 Unsupported Media Type 37
416 Requested Range Not Satisfiable 34 416 Requested Range Not Satisfiable 38
417 Expectation Failed 34 417 Expectation Failed 38
426 Upgrade Required 34 426 Upgrade Required 38
500 Internal Server Error 35 500 Internal Server Error 38
501 Not Implemented 35 501 Not Implemented 39
502 Bad Gateway 35 502 Bad Gateway 39
503 Service Unavailable 35 503 Service Unavailable 39
504 Gateway Timeout 35 504 Gateway Timeout 39
505 HTTP Version Not Supported 36 505 HTTP Version Not Supported 39
T T
TRACE method 21 TRACE method 23
U U
User-Agent header field 41 User-Agent header field 48
Authors' Addresses Authors' Addresses
Roy T. Fielding (editor) Roy T. Fielding (editor)
Adobe Systems Incorporated Adobe Systems Incorporated
345 Park Ave 345 Park Ave
San Jose, CA 95110 San Jose, CA 95110
USA USA
EMail: fielding@gbiv.com EMail: fielding@gbiv.com
 End of changes. 199 change blocks. 
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