draft-ietf-httpbis-p2-semantics-19.txt   draft-ietf-httpbis-p2-semantics-20.txt 
HTTPbis Working Group R. Fielding, Ed. HTTPbis Working Group R. Fielding, Ed.
Internet-Draft Adobe Internet-Draft Adobe
Obsoletes: 2616 (if approved) Y. Lafon, Ed. Obsoletes: 2616 (if approved) Y. Lafon, Ed.
Updates: 2817 (if approved) W3C Updates: 2817 (if approved) W3C
Intended status: Standards Track J. Reschke, Ed. Intended status: Standards Track J. Reschke, Ed.
Expires: September 13, 2012 greenbytes Expires: January 17, 2013 greenbytes
March 12, 2012 July 16, 2012
HTTP/1.1, part 2: Message Semantics HTTP/1.1, part 2: Semantics and Payloads
draft-ietf-httpbis-p2-semantics-19 draft-ietf-httpbis-p2-semantics-20
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. This document defines the semantics of HTTP/1.1 messages,
information initiative since 1990. This document is Part 2 of the as expressed by request methods, request header fields, response
seven-part specification that defines the protocol referred to as status codes, and response header fields, along with the payload of
"HTTP/1.1" and, taken together, obsoletes RFC 2616. messages (metadata and body content) and mechanisms for content
negotiation.
Part 2 defines the semantics of HTTP messages as expressed by request
methods, request header fields, response status codes, and response
header fields.
Editorial Note (To be removed by RFC Editor) Editorial Note (To be removed by RFC Editor)
Discussion of this draft should take place on the HTTPBIS working Discussion of this draft takes place on the HTTPBIS working group
group mailing list (ietf-http-wg@w3.org), which is archived at 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.20. The changes in this draft are summarized in Appendix F.40.
Status of This Memo Status of This Memo
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This Internet-Draft will expire on September 13, 2012. This Internet-Draft will expire on January 17, 2013.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 7
1.1. Conformance and Error Handling . . . . . . . . . . . . . 6 1.1. Conformance and Error Handling . . . . . . . . . . . . . 7
1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 7 1.2. Syntax Notation . . . . . . . . . . . . . . . . . . . . . 8
1.2.1. Core Rules . . . . . . . . . . . . . . . . . . . . . . 7 2. Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
1.2.2. ABNF Rules defined in other Parts of the 2.1. Safe and Idempotent Methods . . . . . . . . . . . . . . . 9
Specification . . . . . . . . . . . . . . . . . . . . 7 2.1.1. Safe Methods . . . . . . . . . . . . . . . . . . . . 9
2. Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.1.2. Idempotent Methods . . . . . . . . . . . . . . . . . 9
2.1. Overview of Methods . . . . . . . . . . . . . . . . . . . 8 2.2. Method Registry . . . . . . . . . . . . . . . . . . . . . 9
2.2. Method Registry . . . . . . . . . . . . . . . . . . . . . 8 2.2.1. Considerations for New Methods . . . . . . . . . . . 10
2.2.1. Considerations for New Methods . . . . . . . . . . . . 9 2.3. Method Definitions . . . . . . . . . . . . . . . . . . . 10
3. Header Fields . . . . . . . . . . . . . . . . . . . . . . . . 9 2.3.1. OPTIONS . . . . . . . . . . . . . . . . . . . . . . . 11
3.1. Considerations for Creating Header Fields . . . . . . . . 9 2.3.2. GET . . . . . . . . . . . . . . . . . . . . . . . . . 12
3.2. Request Header Fields . . . . . . . . . . . . . . . . . . 11 2.3.3. HEAD . . . . . . . . . . . . . . . . . . . . . . . . 12
3.3. Response Header Fields . . . . . . . . . . . . . . . . . 12 2.3.4. POST . . . . . . . . . . . . . . . . . . . . . . . . 13
4. Status Code and Reason Phrase . . . . . . . . . . . . . . . . 12 2.3.5. PUT . . . . . . . . . . . . . . . . . . . . . . . . . 14
4.1. Overview of Status Codes . . . . . . . . . . . . . . . . 13 2.3.6. DELETE . . . . . . . . . . . . . . . . . . . . . . . 16
4.2. Status Code Registry . . . . . . . . . . . . . . . . . . 15 2.3.7. TRACE . . . . . . . . . . . . . . . . . . . . . . . . 16
4.2.1. Considerations for New Status Codes . . . . . . . . . 15 2.3.8. CONNECT . . . . . . . . . . . . . . . . . . . . . . . 17
5. Representation . . . . . . . . . . . . . . . . . . . . . . . . 16 3. Header Fields . . . . . . . . . . . . . . . . . . . . . . . . 18
5.1. Identifying the Resource Associated with a 3.1. Considerations for Creating Header Fields . . . . . . . . 18
Representation . . . . . . . . . . . . . . . . . . . . . 16 3.2. Request Header Fields . . . . . . . . . . . . . . . . . . 20
6. Method Definitions . . . . . . . . . . . . . . . . . . . . . . 17 3.3. Response Header Fields . . . . . . . . . . . . . . . . . 21
6.1. Safe and Idempotent Methods . . . . . . . . . . . . . . . 17 4. Status Codes . . . . . . . . . . . . . . . . . . . . . . . . 22
6.1.1. Safe Methods . . . . . . . . . . . . . . . . . . . . . 17 4.1. Overview of Status Codes . . . . . . . . . . . . . . . . 22
6.1.2. Idempotent Methods . . . . . . . . . . . . . . . . . . 17 4.2. Status Code Registry . . . . . . . . . . . . . . . . . . 24
6.2. OPTIONS . . . . . . . . . . . . . . . . . . . . . . . . . 18 4.2.1. Considerations for New Status Codes . . . . . . . . . 24
6.3. GET . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.3. Informational 1xx . . . . . . . . . . . . . . . . . . . . 25
6.4. HEAD . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.3.1. 100 Continue . . . . . . . . . . . . . . . . . . . . 25
6.5. POST . . . . . . . . . . . . . . . . . . . . . . . . . . 20 4.3.2. 101 Switching Protocols . . . . . . . . . . . . . . . 25
6.6. PUT . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 4.4. Successful 2xx . . . . . . . . . . . . . . . . . . . . . 26
6.7. DELETE . . . . . . . . . . . . . . . . . . . . . . . . . 23 4.4.1. 200 OK . . . . . . . . . . . . . . . . . . . . . . . 26
6.8. TRACE . . . . . . . . . . . . . . . . . . . . . . . . . . 23 4.4.2. 201 Created . . . . . . . . . . . . . . . . . . . . . 26
6.9. CONNECT . . . . . . . . . . . . . . . . . . . . . . . . . 24 4.4.3. 202 Accepted . . . . . . . . . . . . . . . . . . . . 27
7. Status Code Definitions . . . . . . . . . . . . . . . . . . . 25 4.4.4. 203 Non-Authoritative Information . . . . . . . . . . 27
7.1. Informational 1xx . . . . . . . . . . . . . . . . . . . . 26 4.4.5. 204 No Content . . . . . . . . . . . . . . . . . . . 27
7.1.1. 100 Continue . . . . . . . . . . . . . . . . . . . . . 26 4.4.6. 205 Reset Content . . . . . . . . . . . . . . . . . . 28
7.1.2. 101 Switching Protocols . . . . . . . . . . . . . . . 27 4.5. Redirection 3xx . . . . . . . . . . . . . . . . . . . . . 28
7.2. Successful 2xx . . . . . . . . . . . . . . . . . . . . . 27 4.5.1. 300 Multiple Choices . . . . . . . . . . . . . . . . 29
7.2.1. 200 OK . . . . . . . . . . . . . . . . . . . . . . . . 27 4.5.2. 301 Moved Permanently . . . . . . . . . . . . . . . . 30
7.2.2. 201 Created . . . . . . . . . . . . . . . . . . . . . 27 4.5.3. 302 Found . . . . . . . . . . . . . . . . . . . . . . 30
7.2.3. 202 Accepted . . . . . . . . . . . . . . . . . . . . . 28 4.5.4. 303 See Other . . . . . . . . . . . . . . . . . . . . 31
7.2.4. 203 Non-Authoritative Information . . . . . . . . . . 28 4.5.5. 305 Use Proxy . . . . . . . . . . . . . . . . . . . . 31
7.2.5. 204 No Content . . . . . . . . . . . . . . . . . . . . 28 4.5.6. 306 (Unused) . . . . . . . . . . . . . . . . . . . . 31
7.2.6. 205 Reset Content . . . . . . . . . . . . . . . . . . 29 4.5.7. 307 Temporary Redirect . . . . . . . . . . . . . . . 32
7.3. Redirection 3xx . . . . . . . . . . . . . . . . . . . . . 29 4.6. Client Error 4xx . . . . . . . . . . . . . . . . . . . . 32
7.3.1. 300 Multiple Choices . . . . . . . . . . . . . . . . . 31 4.6.1. 400 Bad Request . . . . . . . . . . . . . . . . . . . 32
7.3.2. 301 Moved Permanently . . . . . . . . . . . . . . . . 31 4.6.2. 402 Payment Required . . . . . . . . . . . . . . . . 32
7.3.3. 302 Found . . . . . . . . . . . . . . . . . . . . . . 32 4.6.3. 403 Forbidden . . . . . . . . . . . . . . . . . . . . 32
7.3.4. 303 See Other . . . . . . . . . . . . . . . . . . . . 32 4.6.4. 404 Not Found . . . . . . . . . . . . . . . . . . . . 33
7.3.5. 305 Use Proxy . . . . . . . . . . . . . . . . . . . . 33 4.6.5. 405 Method Not Allowed . . . . . . . . . . . . . . . 33
7.3.6. 306 (Unused) . . . . . . . . . . . . . . . . . . . . . 33 4.6.6. 406 Not Acceptable . . . . . . . . . . . . . . . . . 33
7.3.7. 307 Temporary Redirect . . . . . . . . . . . . . . . . 33 4.6.7. 408 Request Timeout . . . . . . . . . . . . . . . . . 33
7.4. Client Error 4xx . . . . . . . . . . . . . . . . . . . . 33 4.6.8. 409 Conflict . . . . . . . . . . . . . . . . . . . . 34
7.4.1. 400 Bad Request . . . . . . . . . . . . . . . . . . . 33 4.6.9. 410 Gone . . . . . . . . . . . . . . . . . . . . . . 34
7.4.2. 402 Payment Required . . . . . . . . . . . . . . . . . 33 4.6.10. 411 Length Required . . . . . . . . . . . . . . . . . 34
7.4.3. 403 Forbidden . . . . . . . . . . . . . . . . . . . . 33 4.6.11. 413 Request Representation Too Large . . . . . . . . 35
7.4.4. 404 Not Found . . . . . . . . . . . . . . . . . . . . 34 4.6.12. 414 URI Too Long . . . . . . . . . . . . . . . . . . 35
7.4.5. 405 Method Not Allowed . . . . . . . . . . . . . . . . 34 4.6.13. 415 Unsupported Media Type . . . . . . . . . . . . . 35
7.4.6. 406 Not Acceptable . . . . . . . . . . . . . . . . . . 34 4.6.14. 417 Expectation Failed . . . . . . . . . . . . . . . 35
7.4.7. 408 Request Timeout . . . . . . . . . . . . . . . . . 35 4.6.15. 426 Upgrade Required . . . . . . . . . . . . . . . . 35
7.4.8. 409 Conflict . . . . . . . . . . . . . . . . . . . . . 35 4.7. Server Error 5xx . . . . . . . . . . . . . . . . . . . . 36
7.4.9. 410 Gone . . . . . . . . . . . . . . . . . . . . . . . 35 4.7.1. 500 Internal Server Error . . . . . . . . . . . . . . 36
7.4.10. 411 Length Required . . . . . . . . . . . . . . . . . 36 4.7.2. 501 Not Implemented . . . . . . . . . . . . . . . . . 36
7.4.11. 413 Request Representation Too Large . . . . . . . . . 36 4.7.3. 502 Bad Gateway . . . . . . . . . . . . . . . . . . . 36
7.4.12. 414 URI Too Long . . . . . . . . . . . . . . . . . . . 36 4.7.4. 503 Service Unavailable . . . . . . . . . . . . . . . 36
7.4.13. 415 Unsupported Media Type . . . . . . . . . . . . . . 36 4.7.5. 504 Gateway Timeout . . . . . . . . . . . . . . . . . 37
7.4.14. 417 Expectation Failed . . . . . . . . . . . . . . . . 36 4.7.6. 505 HTTP Version Not Supported . . . . . . . . . . . 37
7.4.15. 426 Upgrade Required . . . . . . . . . . . . . . . . . 37 5. Protocol Parameters . . . . . . . . . . . . . . . . . . . . . 37
7.5. Server Error 5xx . . . . . . . . . . . . . . . . . . . . 37 5.1. Date/Time Formats . . . . . . . . . . . . . . . . . . . . 37
7.5.1. 500 Internal Server Error . . . . . . . . . . . . . . 37 5.2. Product Tokens . . . . . . . . . . . . . . . . . . . . . 40
7.5.2. 501 Not Implemented . . . . . . . . . . . . . . . . . 37 5.3. Character Encodings (charset) . . . . . . . . . . . . . . 41
7.5.3. 502 Bad Gateway . . . . . . . . . . . . . . . . . . . 37 5.4. Content Codings . . . . . . . . . . . . . . . . . . . . . 41
7.5.4. 503 Service Unavailable . . . . . . . . . . . . . . . 38 5.4.1. Content Coding Registry . . . . . . . . . . . . . . . 42
7.5.5. 504 Gateway Timeout . . . . . . . . . . . . . . . . . 38 5.5. Media Types . . . . . . . . . . . . . . . . . . . . . . . 42
7.5.6. 505 HTTP Version Not Supported . . . . . . . . . . . . 38 5.5.1. Canonicalization and Text Defaults . . . . . . . . . 43
8. Date/Time Formats . . . . . . . . . . . . . . . . . . . . . . 38 5.5.2. Multipart Types . . . . . . . . . . . . . . . . . . . 44
9. Product Tokens . . . . . . . . . . . . . . . . . . . . . . . . 41 5.6. Language Tags . . . . . . . . . . . . . . . . . . . . . . 44
10. Header Field Definitions . . . . . . . . . . . . . . . . . . . 42 6. Payload . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
10.1. Allow . . . . . . . . . . . . . . . . . . . . . . . . . . 42 6.1. Payload Header Fields . . . . . . . . . . . . . . . . . . 45
10.2. Date . . . . . . . . . . . . . . . . . . . . . . . . . . 42 6.2. Payload Body . . . . . . . . . . . . . . . . . . . . . . 45
10.3. Expect . . . . . . . . . . . . . . . . . . . . . . . . . 43 7. Representation . . . . . . . . . . . . . . . . . . . . . . . 45
10.4. From . . . . . . . . . . . . . . . . . . . . . . . . . . 44 7.1. Identifying the Resource Associated with a
10.5. Location . . . . . . . . . . . . . . . . . . . . . . . . 45 Representation . . . . . . . . . . . . . . . . . . . . . 46
10.6. Max-Forwards . . . . . . . . . . . . . . . . . . . . . . 46 7.2. Representation Header Fields . . . . . . . . . . . . . . 47
10.7. Referer . . . . . . . . . . . . . . . . . . . . . . . . . 46 7.3. Representation Data . . . . . . . . . . . . . . . . . . . 48
10.8. Retry-After . . . . . . . . . . . . . . . . . . . . . . . 47 8. Content Negotiation . . . . . . . . . . . . . . . . . . . . . 49
10.9. Server . . . . . . . . . . . . . . . . . . . . . . . . . 47 8.1. Server-driven Negotiation . . . . . . . . . . . . . . . . 50
10.10. User-Agent . . . . . . . . . . . . . . . . . . . . . . . 48 8.2. Agent-driven Negotiation . . . . . . . . . . . . . . . . 51
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 49 9. Header Field Definitions . . . . . . . . . . . . . . . . . . 52
11.1. Method Registry . . . . . . . . . . . . . . . . . . . . . 49 9.1. Accept . . . . . . . . . . . . . . . . . . . . . . . . . 52
11.2. Status Code Registry . . . . . . . . . . . . . . . . . . 49 9.2. Accept-Charset . . . . . . . . . . . . . . . . . . . . . 54
11.3. Header Field Registration . . . . . . . . . . . . . . . . 50 9.3. Accept-Encoding . . . . . . . . . . . . . . . . . . . . . 55
12. Security Considerations . . . . . . . . . . . . . . . . . . . 51 9.4. Accept-Language . . . . . . . . . . . . . . . . . . . . . 56
12.1. Transfer of Sensitive Information . . . . . . . . . . . . 51 9.5. Allow . . . . . . . . . . . . . . . . . . . . . . . . . . 57
12.2. Encoding Sensitive Information in URIs . . . . . . . . . 52 9.6. Content-Encoding . . . . . . . . . . . . . . . . . . . . 57
12.3. Location Header Fields: Spoofing and Information 9.7. Content-Language . . . . . . . . . . . . . . . . . . . . 58
Leakage . . . . . . . . . . . . . . . . . . . . . . . . . 53 9.8. Content-Location . . . . . . . . . . . . . . . . . . . . 59
12.4. Security Considerations for CONNECT . . . . . . . . . . . 53 9.9. Content-Type . . . . . . . . . . . . . . . . . . . . . . 61
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 53 9.10. Date . . . . . . . . . . . . . . . . . . . . . . . . . . 61
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 53 9.11. Expect . . . . . . . . . . . . . . . . . . . . . . . . . 62
14.1. Normative References . . . . . . . . . . . . . . . . . . 53 9.12. From . . . . . . . . . . . . . . . . . . . . . . . . . . 63
14.2. Informative References . . . . . . . . . . . . . . . . . 54 9.13. Location . . . . . . . . . . . . . . . . . . . . . . . . 63
Appendix A. Changes from RFC 2616 . . . . . . . . . . . . . . . . 55 9.14. Max-Forwards . . . . . . . . . . . . . . . . . . . . . . 65
Appendix B. Collected ABNF . . . . . . . . . . . . . . . . . . . 56 9.15. Referer . . . . . . . . . . . . . . . . . . . . . . . . . 65
Appendix C. Change Log (to be removed by RFC Editor before 9.16. Retry-After . . . . . . . . . . . . . . . . . . . . . . . 66
publication) . . . . . . . . . . . . . . . . . . . . 59 9.17. Server . . . . . . . . . . . . . . . . . . . . . . . . . 66
C.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . 59 9.18. User-Agent . . . . . . . . . . . . . . . . . . . . . . . 67
C.2. Since draft-ietf-httpbis-p2-semantics-00 . . . . . . . . 59 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 67
C.3. Since draft-ietf-httpbis-p2-semantics-01 . . . . . . . . 60 10.1. Method Registry . . . . . . . . . . . . . . . . . . . . . 67
C.4. Since draft-ietf-httpbis-p2-semantics-02 . . . . . . . . 60 10.2. Status Code Registry . . . . . . . . . . . . . . . . . . 68
C.5. Since draft-ietf-httpbis-p2-semantics-03 . . . . . . . . 61 10.3. Header Field Registration . . . . . . . . . . . . . . . . 69
C.6. Since draft-ietf-httpbis-p2-semantics-04 . . . . . . . . 61 10.4. Content Coding Registry . . . . . . . . . . . . . . . . . 70
C.7. Since draft-ietf-httpbis-p2-semantics-05 . . . . . . . . 62 11. Security Considerations . . . . . . . . . . . . . . . . . . . 71
C.8. Since draft-ietf-httpbis-p2-semantics-06 . . . . . . . . 62 11.1. Transfer of Sensitive Information . . . . . . . . . . . . 71
C.9. Since draft-ietf-httpbis-p2-semantics-07 . . . . . . . . 62 11.2. Encoding Sensitive Information in URIs . . . . . . . . . 72
C.10. Since draft-ietf-httpbis-p2-semantics-08 . . . . . . . . 63 11.3. Location Header Fields: Spoofing and Information
C.11. Since draft-ietf-httpbis-p2-semantics-09 . . . . . . . . 63 Leakage . . . . . . . . . . . . . . . . . . . . . . . . . 72
C.12. Since draft-ietf-httpbis-p2-semantics-10 . . . . . . . . 63 11.4. Security Considerations for CONNECT . . . . . . . . . . . 73
C.13. Since draft-ietf-httpbis-p2-semantics-11 . . . . . . . . 64 11.5. Privacy Issues Connected to Accept Header Fields . . . . 73
C.14. Since draft-ietf-httpbis-p2-semantics-12 . . . . . . . . 64 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 74
C.15. Since draft-ietf-httpbis-p2-semantics-13 . . . . . . . . 66 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 74
C.16. Since draft-ietf-httpbis-p2-semantics-14 . . . . . . . . 66 13.1. Normative References . . . . . . . . . . . . . . . . . . 74
C.17. Since draft-ietf-httpbis-p2-semantics-15 . . . . . . . . 66 13.2. Informative References . . . . . . . . . . . . . . . . . 75
C.18. Since draft-ietf-httpbis-p2-semantics-16 . . . . . . . . 66 Appendix A. Differences between HTTP and MIME . . . . . . . . . 77
C.19. Since draft-ietf-httpbis-p2-semantics-17 . . . . . . . . 67 A.1. MIME-Version . . . . . . . . . . . . . . . . . . . . . . 78
C.20. Since draft-ietf-httpbis-p2-semantics-18 . . . . . . . . 67 A.2. Conversion to Canonical Form . . . . . . . . . . . . . . 78
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 A.3. Conversion of Date Formats . . . . . . . . . . . . . . . 79
A.4. Introduction of Content-Encoding . . . . . . . . . . . . 79
A.5. No Content-Transfer-Encoding . . . . . . . . . . . . . . 79
A.6. MHTML and Line Length Limitations . . . . . . . . . . . . 80
Appendix B. Additional Features . . . . . . . . . . . . . . . . 80
Appendix C. Changes from RFC 2616 . . . . . . . . . . . . . . . 80
Appendix D. Imported ABNF . . . . . . . . . . . . . . . . . . . 82
Appendix E. Collected ABNF . . . . . . . . . . . . . . . . . . . 83
Appendix F. Change Log (to be removed by RFC Editor before
publication) . . . . . . . . . . . . . . . . . . . . 85
F.1. Since RFC 2616 . . . . . . . . . . . . . . . . . . . . . 85
F.2. Since draft-ietf-httpbis-p2-semantics-00 . . . . . . . . 86
F.3. Since draft-ietf-httpbis-p3-payload-00 . . . . . . . . . 86
F.4. Since draft-ietf-httpbis-p2-semantics-01 . . . . . . . . 87
F.5. Since draft-ietf-httpbis-p3-payload-01 . . . . . . . . . 88
F.6. Since draft-ietf-httpbis-p2-semantics-02 . . . . . . . . 88
F.7. Since draft-ietf-httpbis-p3-payload-02 . . . . . . . . . 89
F.8. Since draft-ietf-httpbis-p2-semantics-03 . . . . . . . . 89
F.9. Since draft-ietf-httpbis-p3-payload-03 . . . . . . . . . 89
F.10. Since draft-ietf-httpbis-p2-semantics-04 . . . . . . . . 90
F.11. Since draft-ietf-httpbis-p3-payload-04 . . . . . . . . . 90
F.12. Since draft-ietf-httpbis-p2-semantics-05 . . . . . . . . 91
F.13. Since draft-ietf-httpbis-p3-payload-05 . . . . . . . . . 91
F.14. Since draft-ietf-httpbis-p2-semantics-06 . . . . . . . . 91
F.15. Since draft-ietf-httpbis-p3-payload-06 . . . . . . . . . 92
F.16. Since draft-ietf-httpbis-p2-semantics-07 . . . . . . . . 92
F.17. Since draft-ietf-httpbis-p3-payload-07 . . . . . . . . . 92
F.18. Since draft-ietf-httpbis-p2-semantics-08 . . . . . . . . 93
F.19. Since draft-ietf-httpbis-p3-payload-08 . . . . . . . . . 93
F.20. Since draft-ietf-httpbis-p2-semantics-09 . . . . . . . . 93
F.21. Since draft-ietf-httpbis-p3-payload-09 . . . . . . . . . 94
F.22. Since draft-ietf-httpbis-p2-semantics-10 . . . . . . . . 94
F.23. Since draft-ietf-httpbis-p3-payload-10 . . . . . . . . . 95
F.24. Since draft-ietf-httpbis-p2-semantics-11 . . . . . . . . 95
F.25. Since draft-ietf-httpbis-p3-payload-11 . . . . . . . . . 96
F.26. Since draft-ietf-httpbis-p2-semantics-12 . . . . . . . . 96
F.27. Since draft-ietf-httpbis-p3-payload-12 . . . . . . . . . 97
F.28. Since draft-ietf-httpbis-p2-semantics-13 . . . . . . . . 97
F.29. Since draft-ietf-httpbis-p3-payload-13 . . . . . . . . . 98
F.30. Since draft-ietf-httpbis-p2-semantics-14 . . . . . . . . 98
F.31. Since draft-ietf-httpbis-p3-payload-14 . . . . . . . . . 98
F.32. Since draft-ietf-httpbis-p2-semantics-15 . . . . . . . . 98
F.33. Since draft-ietf-httpbis-p3-payload-15 . . . . . . . . . 99
F.34. Since draft-ietf-httpbis-p2-semantics-16 . . . . . . . . 99
F.35. Since draft-ietf-httpbis-p3-payload-16 . . . . . . . . . 99
F.36. Since draft-ietf-httpbis-p2-semantics-17 . . . . . . . . 99
F.37. Since draft-ietf-httpbis-p3-payload-17 . . . . . . . . . 100
F.38. Since draft-ietf-httpbis-p2-semantics-18 . . . . . . . . 100
F.39. Since draft-ietf-httpbis-p3-payload-18 . . . . . . . . . 101
F.40. Since draft-ietf-httpbis-p2-semantics-19 and
draft-ietf-httpbis-p3-payload-19 . . . . . . . . . . . . 101
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
1. Introduction 1. Introduction
This document defines HTTP/1.1 request and response semantics. Each Each HTTP message is either a request or a response. A server
HTTP message, as defined in [Part1], is in the form of either a listens on a connection for a request, parses each message received,
request or a response. An HTTP server listens on a connection for interprets the message semantics in relation to the identified
HTTP requests and responds to each request, in the order received on request target, and responds to that request with one or more
that connection, with one or more HTTP response messages. This response messages. This document defines HTTP/1.1 request and
document defines the commonly agreed upon semantics of the HTTP response semantics in terms of the architecture, syntax notation, and
uniform interface, the intentions defined by each request method, and conformance criteria defined in [Part1].
the various response messages that might be expected as a result of
applying that method to the target resource.
This document is currently disorganized in order to minimize the HTTP provides a uniform interface for interacting with resources
changes between drafts and enable reviewers to see the smaller errata regardless of their type, nature, or implementation. HTTP semantics
changes. A future draft will reorganize the sections to better includes the intentions defined by each request method, extensions to
reflect the content. In particular, the sections will be ordered those semantics that might be described in request header fields, the
according to the typical processing of an HTTP request message (after meaning of status codes to indicate a machine-readable response, and
message parsing): resource mapping, methods, request modifying header additional control data and resource metadata that might be given in
fields, response status, status modifying header fields, and resource response header fields.
metadata. The current mess reflects how widely dispersed these
topics and associated requirements had become in [RFC2616]. In addition, this document defines the payload of messages (a.k.a.,
content), the associated metadata header fields that define how the
payload is intended to be interpreted by a recipient, the request
header fields that might influence content selection, and the various
selection algorithms that are collectively referred to as "content
negotiation".
Note: This document is currently disorganized in order to minimize
changes between drafts and enable reviewers to see the smaller
errata changes. A future draft will reorganize the sections to
better reflect the content. In particular, the sections will be
ordered according to the typical processing of an HTTP request
message (after message parsing): resource mapping, methods,
request modifying header fields, response status, status modifying
header fields, and resource metadata. The current mess reflects
how widely dispersed these topics and associated requirements had
become in [RFC2616].
1.1. Conformance and Error Handling 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].
This document defines conformance criteria for several roles in HTTP This specification targets conformance criteria according to the role
communication, including Senders, Recipients, Clients, Servers, User- of a participant in HTTP communication. Hence, HTTP requirements are
Agents, Origin Servers, Intermediaries, Proxies and Gateways. See placed on senders, recipients, clients, servers, user agents,
Section 2 of [Part1] for definitions of these terms. intermediaries, origin servers, proxies, gateways, or caches,
depending on what behavior is being constrained by the requirement.
See Section 2 of [Part1] for definitions of these terms.
The verb "generate" is used instead of "send" where a requirement
differentiates between creating a protocol element and merely
forwarding a received element downstream.
An implementation is considered conformant if it complies with all of An implementation is considered conformant if it complies with all of
the requirements associated with its role(s). Note that SHOULD-level the requirements associated with the roles it partakes in HTTP. Note
requirements are relevant here, unless one of the documented that SHOULD-level requirements are relevant here, unless one of the
exceptions is applicable. documented exceptions is applicable.
This document also uses ABNF to define valid protocol elements This document also uses ABNF to define valid protocol elements
(Section 1.2). In addition to the prose requirements placed upon (Section 1.2). In addition to the prose requirements placed upon
them, Senders MUST NOT generate protocol elements that are invalid. them, senders MUST NOT generate protocol elements that do not match
the grammar defined by the ABNF rules for those protocol elements
that are applicable to the sender's role. If a received protocol
element is processed, the recipient MUST be able to parse any value
that would match the ABNF rules for that protocol element, excluding
only those rules not applicable to the recipient's role.
Unless noted otherwise, Recipients MAY take steps to recover a usable Unless noted otherwise, a recipient MAY attempt to recover a usable
protocol element from an invalid construct. However, HTTP does not protocol element from an invalid construct. HTTP does not define
define specific error handling mechanisms, except in cases where it specific error handling mechanisms except when they have a direct
has direct impact on security. This is because different uses of the impact on security, since different applications of the protocol
protocol require different error handling strategies; for example, a require different error handling strategies. For example, a Web
Web browser may wish to transparently recover from a response where browser might wish to transparently recover from a response where the
the Location header field doesn't parse according to the ABNF, Location header field doesn't parse according to the ABNF, whereas a
whereby in a systems control protocol using HTTP, this type of error systems control client might consider any form of error recovery to
recovery could lead to dangerous consequences. be dangerous.
1.2. Syntax Notation 1.2. Syntax Notation
This specification uses the Augmented Backus-Naur Form (ABNF) This specification uses the Augmented Backus-Naur Form (ABNF)
notation of [RFC5234] with the list rule extension defined in Section notation of [RFC5234] with the list rule extension defined in Section
1.2 of [Part1]. Appendix B shows the collected ABNF with the list 1.2 of [Part1]. Appendix D describes rules imported from other
rule expanded. documents. Appendix E shows the collected ABNF with the list rule
expanded.
The following core rules are included by reference, as defined in
[RFC5234], Appendix B.1: ALPHA (letters), CR (carriage return), CRLF
(CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double quote),
HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF (line
feed), OCTET (any 8-bit sequence of data), SP (space), and VCHAR (any
visible US-ASCII character).
1.2.1. Core Rules
The core rules below are defined in [Part1]:
BWS = <BWS, defined in [Part1], Section 3.2.1>
OWS = <OWS, defined in [Part1], Section 3.2.1>
RWS = <RWS, defined in [Part1], Section 3.2.1>
obs-text = <obs-text, defined in [Part1], Section 3.2.4>
quoted-string = <quoted-string, defined in [Part1], Section 3.2.4>
token = <token, defined in [Part1], Section 3.2.4>
1.2.2. ABNF Rules defined in other Parts of the Specification
The ABNF rules below are defined in other parts:
absolute-URI = <absolute-URI, defined in [Part1], Section 2.7>
comment = <comment, defined in [Part1], Section 3.2.4>
partial-URI = <partial-URI, defined in [Part1], Section 2.7>
URI-reference = <URI-reference, defined in [Part1], Section 2.7>
2. Method 2. Methods
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 5.5 of [Part1]). The method is case- target resource (Section 5.5 of [Part1]). The method is case-
sensitive. sensitive.
method = token method = token
The list of methods allowed by a resource can be specified in an The list of methods allowed by a resource can be specified in an
Allow header field (Section 10.1). The status code of the response Allow header field (Section 9.5). 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 6. those specified in Section 2.3.
2.1. Overview of Methods 2.1. Safe and Idempotent Methods
The methods listed below are defined in Section 6. 2.1.1. Safe Methods
+-------------+---------------+ Implementers need to be aware that the software represents the user
| Method Name | Defined in... | 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
| OPTIONS | Section 6.2 | significance to themselves or others.
| GET | Section 6.3 |
| HEAD | Section 6.4 |
| POST | Section 6.5 |
| PUT | Section 6.6 |
| DELETE | Section 6.7 |
| TRACE | Section 6.8 |
| CONNECT | Section 6.9 |
+-------------+---------------+
Note that this list is not exhaustive -- it does not include request In particular, the convention has been established that the GET,
methods defined in other specifications. HEAD, OPTIONS, and TRACE request methods SHOULD NOT have the
significance of taking an action other than retrieval. These request
methods ought to be considered "safe". This allows user agents to
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
unsafe action is being requested.
Naturally, it is not possible to ensure that the server does not
generate side-effects as a result of performing a GET request; in
fact, some dynamic resources consider that a feature. The important
distinction here is that the user did not request the side-effects,
so therefore cannot be held accountable for them.
2.1.2. Idempotent Methods
Request methods can also have the property of "idempotence" in that,
aside from error or expiration issues, the intended effect of
multiple identical requests is the same as for a single request.
PUT, DELETE, and all safe request methods are idempotent. It is
important to note that idempotence refers only to changes requested
by the client: a server is free to change its state due to multiple
requests for the purpose of tracking those requests, versioning of
results, etc.
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 6.1.1) o Safe ("yes" or "no", see Section 2.1.1)
o Idempotent ("yes" or "no", see Section 2.1.1)
o Pointer to specification text o Pointer to specification text
Values to be added to this name space require IETF Review (see Values to be added to this name space require IETF Review (see
[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
When it is necessary to express new semantics for a HTTP request that When it is necessary to express new semantics for a HTTP request that
aren't specific to a single application or media type, and currently aren't specific to a single application or media type, and currently
defined methods are inadequate, it may be appropriate to register a defined methods are inadequate, it might be appropriate to register a
new method. new method.
HTTP methods are generic; that is, they are potentially applicable to HTTP methods are generic; that is, they are potentially applicable to
any resource, not just one particular media type, "type" of resource, any resource, not just one particular media type, "type" of resource,
or application. As such, it is preferred that new HTTP methods be or application. As such, it is preferred that new HTTP methods be
registered in a document that isn't specific to a single application, registered in a document that isn't specific to a single application,
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 message definitions of HTTP methods cannot prohibit the presence of a message
body on either the request or the response message (with responses to body on either the request or the response message (with responses to
HEAD requests being the single exception). Definitions of new HEAD requests being the single exception). Definitions of new
methods cannot change this rule, but they can specify that only zero- methods cannot change this rule, but they can specify that only zero-
length bodies (as opposed to absent bodies) are allowed. 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 6.1.1), what semantics (if any) the request body has, and (Section 2.1.1), what semantics (if any) the request body has, and
whether they are idempotent (Section 6.1.2). They also need to state whether they are idempotent (Section 2.1.2). They also need to state
whether they can be cached ([Part6]); in particular what conditions a whether they can be cached ([Part6]); in particular under what
cache may store the response, and under what conditions such a stored conditions a cache can store the response, and under what conditions
response may be used to satisfy a subsequent request. such a stored response can be used to satisfy a subsequent request.
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 extension defined in Section 3.2.5 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 3.2.4 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"
Note that double quote delimiters almost always are used with the
quoted-string production; using a different syntax inside double
quotes will likely cause unnecessary confusion.
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 6.1
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 4.1 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
information about the request, and about the client itself, to the
server. These fields act as request modifiers, with semantics
equivalent to the parameters on a programming language method
invocation.
+---------------------+------------------------+
| Header Field Name | Defined in... |
+---------------------+------------------------+
| Accept | Section 6.1 of [Part3] |
| Accept-Charset | Section 6.2 of [Part3] |
| Accept-Encoding | Section 6.3 of [Part3] |
| Accept-Language | Section 6.4 of [Part3] |
| Authorization | Section 4.1 of [Part7] |
| Expect | Section 10.3 |
| From | Section 10.4 |
| Host | Section 5.4 of [Part1] |
| If-Match | Section 3.1 of [Part4] |
| If-Modified-Since | Section 3.3 of [Part4] |
| If-None-Match | Section 3.2 of [Part4] |
| If-Range | Section 5.3 of [Part5] |
| If-Unmodified-Since | Section 3.4 of [Part4] |
| Max-Forwards | Section 10.6 |
| Proxy-Authorization | Section 4.3 of [Part7] |
| Range | Section 5.4 of [Part5] |
| Referer | Section 10.7 |
| TE | Section 4.3 of [Part1] |
| User-Agent | Section 10.10 |
+---------------------+------------------------+
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 5.5 of [Part1]).
+--------------------+------------------------+
| Header Field Name | Defined in... |
+--------------------+------------------------+
| Accept-Ranges | Section 5.1 of [Part5] |
| Age | Section 3.1 of [Part6] |
| Allow | Section 10.1 |
| Date | Section 10.2 |
| ETag | Section 2.3 of [Part4] |
| Location | Section 10.5 |
| Proxy-Authenticate | Section 4.2 of [Part7] |
| Retry-After | Section 10.8 |
| Server | Section 10.9 |
| Vary | Section 3.5 of [Part6] |
| WWW-Authenticate | Section 4.4 of [Part7] |
+--------------------+------------------------+
4. Status Code and Reason Phrase
The status-code element is a 3-digit integer result code of the
attempt to understand and satisfy the request.
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
not need to examine or display the reason-phrase.
status-code = 3DIGIT
reason-phrase = *( HTAB / SP / VCHAR / obs-text )
HTTP status codes are extensible. HTTP applications are not required
to understand the meaning of all registered status codes, though such
understanding is obviously desirable. However, applications MUST
understand the class of any status code, as indicated by the first
digit, and treat any unrecognized response as being equivalent to the
x00 status code of that class, with the exception that an
unrecognized response MUST NOT be cached. For example, if an
unrecognized status code of 431 is received by the client, it can
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
cases, user agents SHOULD present to the user the representation
enclosed with the response, since that representation is likely to
include human-readable information which will explain the unusual
status.
4.1. Overview of Status Codes
The status codes listed below are defined in Section 7 of this
specification, Section 4 of [Part4], Section 3 of [Part5], and
Section 3 of [Part7]. The reason phrases listed here are only
recommendations -- they can be replaced by local equivalents without
affecting the protocol.
+-------------+------------------------------+----------------------+
| status-code | reason-phrase | Defined in... |
+-------------+------------------------------+----------------------+
| 100 | Continue | Section 7.1.1 |
| 101 | Switching Protocols | Section 7.1.2 |
| 200 | OK | Section 7.2.1 |
| 201 | Created | Section 7.2.2 |
| 202 | Accepted | Section 7.2.3 |
| 203 | Non-Authoritative | Section 7.2.4 |
| | Information | |
| 204 | No Content | Section 7.2.5 |
| 205 | Reset Content | Section 7.2.6 |
| 206 | Partial Content | Section 3.1 of |
| | | [Part5] |
| 300 | Multiple Choices | Section 7.3.1 |
| 301 | Moved Permanently | Section 7.3.2 |
| 302 | Found | Section 7.3.3 |
| 303 | See Other | Section 7.3.4 |
| 304 | Not Modified | Section 4.1 of |
| | | [Part4] |
| 305 | Use Proxy | Section 7.3.5 |
| 307 | Temporary Redirect | Section 7.3.7 |
| 400 | Bad Request | Section 7.4.1 |
| 401 | Unauthorized | Section 3.1 of |
| | | [Part7] |
| 402 | Payment Required | Section 7.4.2 |
| 403 | Forbidden | Section 7.4.3 |
| 404 | Not Found | Section 7.4.4 |
| 405 | Method Not Allowed | Section 7.4.5 |
| 406 | Not Acceptable | Section 7.4.6 |
| 407 | Proxy Authentication | Section 3.2 of |
| | Required | [Part7] |
| 408 | Request Time-out | Section 7.4.7 |
| 409 | Conflict | Section 7.4.8 |
| 410 | Gone | Section 7.4.9 |
| 411 | Length Required | Section 7.4.10 |
| 412 | Precondition Failed | Section 4.2 of |
| | | [Part4] |
| 413 | Request Representation Too | Section 7.4.11 |
| | Large | |
| 414 | URI Too Long | Section 7.4.12 |
| 415 | Unsupported Media Type | Section 7.4.13 |
| 416 | Requested range not | Section 3.2 of |
| | satisfiable | [Part5] |
| 417 | Expectation Failed | Section 7.4.14 |
| 426 | Upgrade Required | Section 7.4.15 |
| 500 | Internal Server Error | Section 7.5.1 |
| 501 | Not Implemented | Section 7.5.2 |
| 502 | Bad Gateway | Section 7.5.3 |
| 503 | Service Unavailable | Section 7.5.4 |
| 504 | Gateway Time-out | Section 7.5.5 |
| 505 | HTTP Version not supported | Section 7.5.6 |
+-------------+------------------------------+----------------------+
Note that this list is not exhaustive -- it does not include
extension status codes defined in other specifications.
4.2. Status Code Registry
The HTTP Status Code Registry defines the name space for the status-
code token in the status-line of an HTTP response.
Values to be added to this name space require IETF Review (see
[RFC5226], Section 4.1).
The registry itself is maintained at
<http://www.iana.org/assignments/http-status-codes>.
4.2.1. Considerations for New Status Codes
When it is necessary to express new semantics for a HTTP response
that aren't specific to a single application or media type, and
currently defined status codes are inadequate, a new status code can
be registered.
HTTP status codes are generic; that is, they are potentially
applicable to any resource, not just one particular media type,
"type" of resource, or application. As such, it is preferred that
new HTTP status codes be registered in a document that isn't specific
to a single application, so that this is clear.
Definitions of new HTTP status codes typically explain the request
conditions that produce a response containing the status code (e.g.,
combinations of request headers and/or method(s)), along with any
interactions with response headers (e.g., those that are required,
those that modify the semantics of the response).
New HTTP status codes are required to fall under one of the
categories defined in Section 7. To allow existing parsers to
properly handle them, new status codes cannot disallow a response
body, although they can mandate a zero-length response body. They
can require the presence of one or more particular HTTP response
header(s).
Likewise, their definitions can specify that caches are allowed to
use heuristics to determine their freshness (see [Part6]; by default,
it is not allowed), and can define how to determine the resource
which they carry a representation for (see Section 5.1; by default,
it is anonymous).
5. Representation
Request and Response messages MAY transfer a representation if not
otherwise restricted by the request method or response status code.
A representation consists of metadata (representation header fields)
and data (representation body). When a complete or partial
representation is enclosed in an HTTP message, it is referred to as
the payload of the message. HTTP representations are defined in
[Part3].
A representation body is only present in a message when a message
body is present, as described in Section 3.3 of [Part1]. The
representation body is obtained from the message body by decoding any
Transfer-Encoding that might have been applied to ensure safe and
proper transfer of the message.
5.1. Identifying the Resource Associated with a Representation
It is sometimes necessary to determine an identifier for the resource
associated with a representation.
An HTTP request representation, when present, is always associated
with an anonymous (i.e., unidentified) resource.
In the common case, an HTTP response is a representation of the
target resource (see Section 5.5 of [Part1]). However, this is not
always the case. To determine the URI of the resource a response is
associated with, the following rules are used (with the first
applicable one being selected):
1. If the response status code is 200 or 203 and the request method
was GET, the response payload is a representation of the target
resource.
2. If the response status code is 204, 206, or 304 and the request
method was GET or HEAD, the response payload is a partial
representation of the target resource.
3. If the response has a Content-Location header field, and that URI
is the same as the effective request URI, the response payload is
a representation of the target resource.
4. If the response has a Content-Location header field, and that URI
is not the same as the effective request URI, then the response
asserts that its payload is a representation of the resource
identified by the Content-Location URI. However, such an
assertion cannot be trusted unless it can be verified by other
means (not defined by HTTP).
5. Otherwise, the response is a representation of an anonymous
(i.e., unidentified) resource.
[[TODO-req-uri: The comparison function is going to have to be
defined somewhere, because we already need to compare URIs for things
like cache invalidation.]]
6. Method Definitions
The set of common request methods for HTTP/1.1 is defined below.
Although this set can be expanded, additional methods cannot be
assumed to share the same semantics for separately extended clients
and servers.
6.1. Safe and Idempotent Methods
6.1.1. Safe Methods
Implementors need to be aware that the software represents 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
significance to themselves or others.
In particular, the convention has been established that the GET,
HEAD, OPTIONS, and TRACE request methods SHOULD NOT have the
significance of taking an action other than retrieval. These request
methods ought to be considered "safe". This allows user agents to
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
unsafe action is being requested.
Naturally, it is not possible to ensure that the server does not
generate side-effects as a result of performing a GET request; in
fact, some dynamic resources consider that a feature. The important
distinction here is that the user did not request the side-effects,
so therefore cannot be held accountable for them.
6.1.2. Idempotent Methods
Request methods can also have the property of "idempotence" in that,
aside from error or expiration issues, the intended effect of
multiple identical requests is the same as for a single request.
PUT, DELETE, and all safe request methods are idempotent. It is
important to note that idempotence refers only to changes requested
by the client: a server is free to change its state due to multiple
requests for the purpose of tracking those requests, versioning of
results, etc.
6.2. OPTIONS 2.3. Method Definitions
2.3.1. 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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options typically depend on the resource, the "*" request is only options typically depend on the resource, the "*" request is only
useful as a "ping" or "no-op" type of method; it does nothing beyond useful as a "ping" or "no-op" type of method; it does nothing beyond
allowing the client to test the capabilities of the server. For allowing the client to test the capabilities of the server. For
example, this can be used to test a proxy for HTTP/1.1 conformance example, this can be used to test a proxy for HTTP/1.1 conformance
(or lack thereof). (or lack thereof).
If the request-target is not an asterisk, the OPTIONS request applies If the request-target is not an asterisk, the OPTIONS request applies
only to the options that are available when communicating with that only to the options that are available when communicating with that
resource. resource.
A 200 response SHOULD include any header fields that indicate A 200 (OK) response SHOULD include any header fields that indicate
optional features implemented by the server and applicable to that optional features implemented by the server and applicable to that
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 10.6). If no Max-Forwards field is in the request chain (see Section 9.14). 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.
6.3. GET 2.3.2. 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
request message includes an If-Modified-Since, If-Unmodified-Since, request message includes an If-Modified-Since, If-Unmodified-Since,
If-Match, If-None-Match, or If-Range header field. A conditional GET If-Match, If-None-Match, or If-Range header field ([Part4]). A
requests that the representation be transferred only under the conditional GET requests that the representation be transferred only
circumstances described by the conditional header field(s). The under the circumstances described by the conditional header field(s).
conditional GET request is intended to reduce unnecessary network The conditional GET request is intended to reduce unnecessary network
usage by allowing cached representations to be refreshed without usage by allowing cached representations to be refreshed without
requiring multiple requests or transferring data already held by the requiring multiple requests or transferring data already held by the
client. client.
The semantics of the GET method change to a "partial GET" if the The semantics of the GET method change to a "partial GET" if the
request message includes a Range header field. A partial GET request message includes a Range header field ([Part5]). A partial
requests that only part of the representation be transferred, as GET requests that only part of the representation be transferred, as
described in Section 5.4 of [Part5]. The partial GET request is described in Section 5.4 of [Part5]. The partial GET request is
intended to reduce unnecessary network usage by allowing partially- intended to reduce unnecessary network usage by allowing partially-
retrieved representations to be completed without transferring data retrieved representations to be completed without transferring data
already held by the client. already held by the client.
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 12.2 for security considerations when used for forms. See Section 11.2 for security considerations when used for forms.
6.4. HEAD 2.3.3. 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.
The response to a HEAD request is cacheable and MAY be used to The response to a HEAD request is cacheable and MAY be used to
satisfy a subsequent HEAD request. It also has potential side satisfy a subsequent HEAD request. It also has potential side
effects on previously stored responses to GET; see Section 2.5 of effects on previously stored responses to GET; see Section 5 of
[Part6]. [Part6].
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.
6.5. POST 2.3.4. 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 10.5). Location header field (see Section 9.13).
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 4.1.1 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 9.8) whose value is the effective Request URI MAY be used to
be used to satisfy subsequent GET and HEAD requests. 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 representation of the resource.
6.6. PUT 2.3.5. 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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server SHOULD either make them consistent, by transforming the server SHOULD either make them consistent, by transforming the
representation or changing the resource configuration, or respond representation or changing the resource configuration, or respond
with an appropriate error message containing sufficient information with an appropriate error message containing sufficient information
to explain why the representation is unsuitable. The 409 (Conflict) to explain why the representation is unsuitable. The 409 (Conflict)
or 415 (Unsupported Media Type) status codes are suggested, with the or 415 (Unsupported Media Type) status codes are suggested, with the
latter being specific to constraints on Content-Type values. latter being specific to constraints on Content-Type values.
For example, if the target resource is configured to always have a For example, if the target resource is configured to always have a
Content-Type of "text/html" and the representation being PUT has a Content-Type of "text/html" and the representation being PUT has a
Content-Type of "image/jpeg", then the origin server SHOULD do one Content-Type of "image/jpeg", then the origin server SHOULD do one
of: (a) reconfigure the target resource to reflect the new media of:
type; (b) transform the PUT representation to a format consistent
with that of the resource before saving it as the new resource state; a. reconfigure the target resource to reflect the new media type;
or, (c) reject the request with a 415 response indicating that the
target resource is limited to "text/html", perhaps including a link b. transform the PUT representation to a format consistent with that
to a different resource that would be a suitable target for the new of the resource before saving it as the new resource state; or,
representation.
c. reject the request with a 415 (Unsupported Media Type) response
indicating that the target resource is limited to "text/html",
perhaps including a link to a different resource that would be a
suitable target for the new representation.
HTTP does not define exactly how a PUT method affects the state of an HTTP does not define exactly how a PUT method affects the state of an
origin server beyond what can be expressed by the intent of the user origin server beyond what can be expressed by the intent of the user
agent request and the semantics of the origin server response. It agent request and the semantics of the origin server response. It
does not define what a resource might be, in any sense of that word, does not define what a resource might be, in any sense of that word,
beyond the interface provided via HTTP. It does not define how beyond the interface provided via HTTP. It does not define how
resource state is "stored", nor how such storage might change as a resource state is "stored", nor how such storage might change as a
result of a change in resource state, nor how the origin server result of a change in resource state, nor how the origin server
translates resource state into representations. Generally speaking, translates resource state into representations. Generally speaking,
all implementation details behind the resource interface are all implementation details behind the resource interface are
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other resources. For example, an article might have a URI for other resources. For example, an article might have a URI for
identifying "the current version" (a resource) which is separate from identifying "the current version" (a resource) which is separate from
the URIs identifying each particular version (different resources the URIs identifying each particular version (different resources
that at one point shared the same state as the current version that at one point shared the same state as the current version
resource). A successful PUT request on "the current version" URI resource). A successful PUT request on "the current version" URI
might therefore create a new version resource in addition to changing might therefore create a new version resource in addition to changing
the state of the target resource, and might also cause links to be the state of the target resource, and might also cause links to be
added between the related resources. added between the related resources.
An origin server SHOULD reject any PUT request that contains a An origin server SHOULD reject any PUT request that contains a
Content-Range header field, since it might be misinterpreted as Content-Range header field (Section 5.2 of [Part5]), since it might
partial content (or might be partial content that is being mistakenly be misinterpreted as partial content (or might be partial content
PUT as a full representation). Partial content updates are possible that is being mistakenly PUT as a full representation). Partial
by targeting a separately identified resource with state that content updates are possible by targeting a separately identified
overlaps a portion of the larger resource, or by using a different resource with state that overlaps a portion of the larger resource,
method that has been specifically defined for partial updates (for or by using a different method that has been specifically defined for
example, the PATCH method defined in [RFC5789]). partial updates (for 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 2.6 of [Part6]). (see Section 6 of [Part6]).
6.7. DELETE 2.3.6. 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.
A successful response SHOULD be 200 (OK) if the response includes an A successful response SHOULD be 200 (OK) if the response includes a
representation describing the status, 202 (Accepted) if the action representation describing the status, 202 (Accepted) if the action
has not yet been enacted, or 204 (No Content) if the action has been has not yet been enacted, or 204 (No Content) if the action has been
enacted but the response does not include a representation. enacted but the response does not include a representation.
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 2.6 of [Part6]). invalidated (see Section 6 of [Part6]).
6.8. TRACE 2.3.7. 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 10.6). A TRACE request MUST NOT include in the request (see Section 9.14). A TRACE request MUST NOT include
a message body. a 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 6.2 of information. The value of the Via header field (Section 6.2 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 7.3.1 of [Part1]) and contain a message "message/http" (see Section 7.3.1 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.
6.9. CONNECT 2.3.8. 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, if successful, thereafter restrict its behavior request-target and, if successful, thereafter restrict its behavior
to blind forwarding of packets until the connection is closed. to blind forwarding of 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 5.3 of [Part1]); i.e., the request-target consists of only (Section 5.3 of [Part1]); i.e., the request-target consists of only
the host name and port number of the tunnel destination, separated by the host name and port number of the tunnel destination, separated by
a colon. For example, 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
Any successful (2xx) response to a CONNECT request indicates that the Any 2xx (Successful) 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. The tunneled data from the server begins immediately connection. The tunneled data from the server begins immediately
after the blank line that concludes the successful response's header after the blank line that concludes the successful response's header
block. A server SHOULD NOT send any Transfer-Encoding or Content- block.
Length header fields in a successful response. A client MUST ignore
any Content-Length or Transfer-Encoding header fields received in a A server SHOULD NOT send any Transfer-Encoding or Content-Length
header fields in a successful response. A client MUST ignore any
Content-Length or Transfer-Encoding header fields received in a
successful response. successful response.
Any response other than a successful response indicates that the Any response other than a successful response indicates that the
tunnel has not yet been formed and that the connection remains tunnel has not yet been formed and that the connection remains
governed by HTTP. governed by HTTP.
Proxy authentication might be used to establish the authority to Proxy authentication might be used to establish the authority to
create a tunnel: create a tunnel:
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
Proxy-Authorization: basic aGVsbG86d29ybGQ= Proxy-Authorization: basic aGVsbG86d29ybGQ=
A message body on a CONNECT request has no defined semantics. A message body on a CONNECT request has no defined semantics.
Sending a body on a CONNECT request might cause existing Sending a body on a CONNECT request might cause existing
implementations to reject the request. implementations to reject the request.
Similar to a pipelined HTTP/1.1 request, data to be tunneled from Similar to a pipelined HTTP/1.1 request, data to be tunneled from
client to server MAY be sent immediately after the request (before a client to server MAY be sent immediately after the request (before a
response is received). The usual caveats also apply: data may be response is received). The usual caveats also apply: data can be
discarded if the eventual response is negative, and the connection discarded if the eventual response is negative, and the connection
may be reset with no response if more than one TCP segment is can be reset with no response if more than one TCP segment is
outstanding. outstanding.
It may be the case that the proxy itself can only reach the requested It might be the case that the proxy itself can only reach the
origin server through another proxy. In this case, the first proxy requested origin server through another proxy. In this case, the
SHOULD make a CONNECT request of that next proxy, requesting a tunnel first proxy SHOULD make a CONNECT request of that next proxy,
to the authority. A proxy MUST NOT respond with any 2xx status code requesting a tunnel to the authority. A proxy MUST NOT respond with
unless it has either a direct or tunnel connection established to the any 2xx status code unless it has either a direct or tunnel
authority. connection established to the authority.
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.
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. However, most origin servers do not implement CONNECT. established. However, most origin servers do not implement CONNECT.
7. Status Code Definitions 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 extension defined in Appendix B 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 3.2.4 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"
Note that double quote delimiters almost always are used with the
quoted-string production; using a different syntax inside double
quotes will likely cause unnecessary confusion.
Many header fields use a format including (case-insensitively) named
parameters (for instance, Content-Type, defined in Section 9.9).
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 5.5).
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 field (i.e., if the header field is to be hop-by-hop, see
Section 6.1 of [Part1]).
o Under what conditions intermediaries are allowed to modify the
header field's value, insert or delete it.
o How the header field might interact with caching (see [Part6]).
o Whether the header field is useful or allowable in trailers (see
Section 4.1 of [Part1]).
o Whether the header field ought to be preserved across redirects.
3.2. Request Header Fields
The request header fields allow the client to pass additional
information about the request, and about the client itself, to the
server. These fields act as request modifiers, with semantics
equivalent to the parameters on a programming language method
invocation.
+---------------------+------------------------+
| Header Field Name | Defined in... |
+---------------------+------------------------+
| Accept | Section 9.1 |
| Accept-Charset | Section 9.2 |
| Accept-Encoding | Section 9.3 |
| Accept-Language | Section 9.4 |
| Authorization | Section 4.1 of [Part7] |
| Expect | Section 9.11 |
| From | Section 9.12 |
| Host | Section 5.4 of [Part1] |
| If-Match | Section 3.1 of [Part4] |
| If-Modified-Since | Section 3.3 of [Part4] |
| If-None-Match | Section 3.2 of [Part4] |
| If-Range | Section 5.3 of [Part5] |
| If-Unmodified-Since | Section 3.4 of [Part4] |
| Max-Forwards | Section 9.14 |
| Proxy-Authorization | Section 4.3 of [Part7] |
| Range | Section 5.4 of [Part5] |
| Referer | Section 9.15 |
| TE | Section 4.3 of [Part1] |
| User-Agent | Section 9.18 |
+---------------------+------------------------+
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 5.5 of [Part1]).
+--------------------+------------------------+
| Header Field Name | Defined in... |
+--------------------+------------------------+
| Accept-Ranges | Section 5.1 of [Part5] |
| Age | Section 7.1 of [Part6] |
| Allow | Section 9.5 |
| Date | Section 9.10 |
| ETag | Section 2.3 of [Part4] |
| Location | Section 9.13 |
| Proxy-Authenticate | Section 4.2 of [Part7] |
| Retry-After | Section 9.16 |
| Server | Section 9.17 |
| Vary | Section 7.5 of [Part6] |
| WWW-Authenticate | Section 4.4 of [Part7] |
+--------------------+------------------------+
4. Status Codes
The status-code element is a 3-digit integer result code of the
attempt to understand and satisfy the request.
HTTP status codes are extensible. HTTP applications are not required
to understand the meaning of all registered status codes, though such
understanding is obviously desirable. However, applications MUST
understand the class of any status code, as indicated by the first
digit, and treat any unrecognized response as being equivalent to the
x00 status code of that class, with the exception that an
unrecognized response MUST NOT be cached. For example, if an
unrecognized status code of 431 is received by the client, it can
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
cases, user agents SHOULD present to the user the representation
enclosed with the response, since that representation is likely to
include human-readable information which will explain the unusual
status.
The first digit of the status-code defines the class of response. 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 The last two digits do not have any categorization role. There are 5
values for the first digit: values for the first digit:
o 1xx: Informational - Request received, continuing process o 1xx (Informational): Request received, continuing process
o 2xx: Success - The action was successfully received, understood, o 2xx (Successful): The action was successfully received,
and accepted understood, and accepted
o 3xx: Redirection - Further action must be taken in order to o 3xx (Redirection): Further action needs to be taken in order to
complete the request complete the request
o 4xx: Client Error - The request contains bad syntax or cannot be o 4xx (Client Error): The request contains bad syntax or cannot be
fulfilled fulfilled
o 5xx: Server Error - The server failed to fulfill an apparently o 5xx (Server Error): The server failed to fulfill an apparently
valid request valid request
Each status-code is described below, including any metadata required
in the response.
For most status codes the response can carry a payload, in which case For most status codes the response can carry a payload, in which case
a Content-Type header field indicates the payload's media type a Content-Type header field indicates the payload's media type
(Section 6.8 of [Part3]). (Section 9.9).
7.1. Informational 1xx 4.1. Overview of Status Codes
The status codes listed below are defined in this specification,
Section 4 of [Part4], Section 3 of [Part5], and Section 3 of [Part7].
The reason phrases listed here are only recommendations -- they can
be replaced by local equivalents without affecting the protocol.
+-------------+------------------------------+----------------------+
| status-code | reason-phrase | Defined in... |
+-------------+------------------------------+----------------------+
| 100 | Continue | Section 4.3.1 |
| 101 | Switching Protocols | Section 4.3.2 |
| 200 | OK | Section 4.4.1 |
| 201 | Created | Section 4.4.2 |
| 202 | Accepted | Section 4.4.3 |
| 203 | Non-Authoritative | Section 4.4.4 |
| | Information | |
| 204 | No Content | Section 4.4.5 |
| 205 | Reset Content | Section 4.4.6 |
| 206 | Partial Content | Section 3.1 of |
| | | [Part5] |
| 300 | Multiple Choices | Section 4.5.1 |
| 301 | Moved Permanently | Section 4.5.2 |
| 302 | Found | Section 4.5.3 |
| 303 | See Other | Section 4.5.4 |
| 304 | Not Modified | Section 4.1 of |
| | | [Part4] |
| 305 | Use Proxy | Section 4.5.5 |
| 307 | Temporary Redirect | Section 4.5.7 |
| 400 | Bad Request | Section 4.6.1 |
| 401 | Unauthorized | Section 3.1 of |
| | | [Part7] |
| 402 | Payment Required | Section 4.6.2 |
| 403 | Forbidden | Section 4.6.3 |
| 404 | Not Found | Section 4.6.4 |
| 405 | Method Not Allowed | Section 4.6.5 |
| 406 | Not Acceptable | Section 4.6.6 |
| 407 | Proxy Authentication | Section 3.2 of |
| | Required | [Part7] |
| 408 | Request Time-out | Section 4.6.7 |
| 409 | Conflict | Section 4.6.8 |
| 410 | Gone | Section 4.6.9 |
| 411 | Length Required | Section 4.6.10 |
| 412 | Precondition Failed | Section 4.2 of |
| | | [Part4] |
| 413 | Request Representation Too | Section 4.6.11 |
| | Large | |
| 414 | URI Too Long | Section 4.6.12 |
| 415 | Unsupported Media Type | Section 4.6.13 |
| 416 | Requested range not | Section 3.2 of |
| | satisfiable | [Part5] |
| 417 | Expectation Failed | Section 4.6.14 |
| 426 | Upgrade Required | Section 4.6.15 |
| 500 | Internal Server Error | Section 4.7.1 |
| 501 | Not Implemented | Section 4.7.2 |
| 502 | Bad Gateway | Section 4.7.3 |
| 503 | Service Unavailable | Section 4.7.4 |
| 504 | Gateway Time-out | Section 4.7.5 |
| 505 | HTTP Version not supported | Section 4.7.6 |
+-------------+------------------------------+----------------------+
Note that this list is not exhaustive -- it does not include
extension status codes defined in other specifications.
4.2. Status Code Registry
The HTTP Status Code Registry defines the name space for the status-
code token in the status-line of an HTTP response.
Values to be added to this name space require IETF Review (see
[RFC5226], Section 4.1).
The registry itself is maintained at
<http://www.iana.org/assignments/http-status-codes>.
4.2.1. Considerations for New Status Codes
When it is necessary to express new semantics for a HTTP response
that aren't specific to a single application or media type, and
currently defined status codes are inadequate, a new status code can
be registered.
HTTP status codes are generic; that is, they are potentially
applicable to any resource, not just one particular media type,
"type" of resource, or application. As such, it is preferred that
new HTTP status codes be registered in a document that isn't specific
to a single application, so that this is clear.
Definitions of new HTTP status codes typically explain the request
conditions that produce a response containing the status code (e.g.,
combinations of request header fields and/or method(s)), along with
any interactions with response header fields (e.g., those that are
required, those that modify the semantics of the response).
New HTTP status codes are required to fall under one of the
categories defined in Section 4. To allow existing parsers to
properly handle them, new status codes cannot disallow a response
body, although they can mandate a zero-length response body. They
can require the presence of one or more particular HTTP response
header field(s).
Likewise, their definitions can specify that caches are allowed to
use heuristics to determine their freshness (see [Part6]; by default,
it is not allowed), and can define how to determine the resource
which they carry a representation for (see Section 7.1; by default,
it is anonymous).
4.3. 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 an "Expect: 100-continue" field when it forwards a
then it need not forward the corresponding 100 (Continue) request, then it need not forward the corresponding 100 (Continue)
response(s).) response(s).)
7.1.1. 100 Continue 4.3.1. 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 6.4.3 of [Part1] for detailed discussion of completed. See Section 6.4.3 of [Part1] for detailed discussion of
the use and handling of this status code. the use and handling of this status code.
7.1.2. 101 Switching Protocols 4.3.2. 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 6.5 of request, via the Upgrade message header field (Section 6.5 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.
7.2. Successful 2xx 4.4. 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.
7.2.1. 200 OK 4.4.1. 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 4.1.2 of [Part6]) to
determine freshness for 200 responses. determine freshness for 200 responses.
7.2.2. 201 Created 4.4.2. 201 Created
The request has been fulfilled and has resulted in a new resource The request has been fulfilled and has resulted in one or more new
being created. resources being created.
The newly created resource is typically linked to from the response Newly created resources are typically linked to from the response
payload, with the most relevant URI also being carried in the payload, with the most relevant URI also being carried in the
Location header field. If the newly created resource's URI is the Location header field. If the newly created resource's URI is the
same as the Effective Request URI, this information can be omitted same as the Effective Request URI, this information can be omitted
(e.g., in the case of a response to a PUT request). (e.g., in the case of a response to a PUT request).
The origin server MUST create the resource before returning the 201 The origin server MUST create the resource(s) before returning the
status code. If the action cannot be carried out immediately, the 201 status code. If the action cannot be carried out immediately,
server SHOULD respond with 202 (Accepted) response instead. the server SHOULD 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 identified by the Location header field or, in case the
Location header field was omitted, by the Effective Request URI (see
Section 2.3 of [Part4]).
7.2.3. 202 Accepted 4.4.3. 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.
7.2.4. 203 Non-Authoritative Information 4.4.4. 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 2.3 of [Part1]). Note that modified by a transforming proxy (Section 2.4 of [Part1]). Note that
the behavior of transforming intermediaries is controlled by the no- the behavior of transforming intermediaries is controlled by the no-
transform Cache-Control directive (Section 3.2 of [Part6]). transform Cache-Control directive (Section 7.2 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 7.6 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 4.1.2 of [Part6]) to
determine freshness for 203 responses. determine freshness for 203 responses.
7.2.5. 204 No Content 4.4.5. 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
skipping to change at page 29, line 28 skipping to change at page 28, line 18
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.
7.2.6. 205 Reset Content 4.4.6. 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].
7.3. Redirection 3xx 4.5. 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. If the taken by the user agent in order to fulfill the request. If the
required action involves a subsequent HTTP request, it MAY be carried required action involves a subsequent HTTP request, it MAY be carried
out by the user agent without interaction with the user if and only out by the user agent without interaction with the user if and only
if the method used in the second request is known to be "safe", as if the method used in the second request is known to be "safe", as
defined in Section 6.1.1. defined in Section 2.1.1.
There are several types of redirects: There are several types of redirects:
1. Redirects of the request to another URI, either temporarily or 1. Redirects of the request to another URI, either temporarily or
permanently. The new URI is specified in the Location header permanently. The new URI is specified in the Location header
field. In this specification, the status codes 301 (Moved field. In this specification, the status codes 301 (Moved
Permanently), 302 (Found), and 307 (Temporary Redirect) fall Permanently), 302 (Found), and 307 (Temporary Redirect) fall
under this category. under this category.
2. Redirection to a new location that represents an indirect 2. Redirection to a new location that represents an indirect
response to the request, such as the result of a POST operation response to the request, such as the result of a POST operation
to be retrieved with a subsequent GET request. This is status to be retrieved with a subsequent GET request. This is status
code 303 (See Other). code 303 (See Other).
3. Redirection offering a choice of matching resources for use by 3. Redirection offering a choice of matching resources for use by
agent-driven content negotiation (Section 5.2 of [Part3]). This agent-driven content negotiation (Section 8.2). This is status
is status code 300 (Multiple Choices). code 300 (Multiple Choices).
4. Other kinds of redirection, such as to a cached result (status 4. Other kinds of redirection, such as to a cached result (status
code 304 (Not Modified), see Section 4.1 of [Part4]). code 304 (Not Modified), see Section 4.1 of [Part4]).
Note: In HTTP/1.0, only the status codes 301 (Moved Permanently) Note: In HTTP/1.0, only the status codes 301 (Moved Permanently)
and 302 (Found) were defined for the first type of redirect, and and 302 (Found) were defined for the first type of redirect, and
the second type did not exist at all ([RFC1945], Section 9.3). the second type did not exist at all ([RFC1945], Section 9.3).
However it turned out that web forms using POST expected redirects However it turned out that web forms using POST expected redirects
to change the operation for the subsequent request to retrieval to change the operation for the subsequent request to retrieval
(GET). To address this use case, HTTP/1.1 introduced the second (GET). To address this use case, HTTP/1.1 introduced the second
skipping to change at page 30, line 40 skipping to change at page 29, line 29
Section 10.3.4). As user agents did not change their behavior to Section 10.3.4). As user agents did not change their behavior to
maintain backwards compatibility, the first revision of HTTP/1.1 maintain backwards compatibility, the first revision of HTTP/1.1
added yet another status code, 307 (Temporary Redirect), for which added yet another status code, 307 (Temporary Redirect), for which
the backwards compatibility problems did not apply ([RFC2616], the backwards compatibility problems did not apply ([RFC2616],
Section 10.3.8). Over 10 years later, most user agents still do Section 10.3.8). Over 10 years later, most user agents still do
method rewriting for status codes 301 and 302, therefore this method rewriting for status codes 301 and 302, therefore this
specification makes that behavior conformant in case the original specification makes that behavior conformant in case the original
request was POST. request was POST.
A Location header field on a 3xx response indicates that a client MAY A Location header field on a 3xx response indicates that a client MAY
automatically redirect to the URI provided; see Section 10.5. automatically redirect to the URI provided; see Section 9.13.
Note that for methods not known to be "safe", as defined in Note that for methods not known to be "safe", as defined in
Section 6.1.1, automatic redirection needs to done with care, since Section 2.1.1, automatic redirection needs to done with care, since
the redirect might change the conditions under which the request was the redirect might change the conditions under which the request was
issued. issued.
Clients SHOULD detect and intervene in cyclical redirections (i.e., Clients SHOULD detect and intervene in cyclical redirections (i.e.,
"infinite" redirection loops). "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.
7.3.1. 300 Multiple Choices 4.5.1. 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 8) is being provided so that the user (or user agent) can
agent) can select a preferred representation by redirecting its select a preferred representation by redirecting its request to that
request to that location. 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
appropriate. Depending upon the format and the capabilities of the appropriate. Depending upon the format and the capabilities of the
user agent, selection of the most appropriate choice MAY be performed user agent, selection of the most appropriate choice MAY be performed
automatically. However, this specification does not define any automatically. However, this specification does not define any
standard for such automatic selection. 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 4.1.2 of [Part6]) to
determine freshness for 300 responses. determine freshness for 300 responses.
7.3.2. 301 Moved Permanently 4.5.2. 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 4.1.2 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. A response payload can contain a short hypertext note with response. A response payload can contain a short hypertext note with
a hyperlink to the new URI(s). a hyperlink to the new URI(s).
Note: For historic reasons, user agents MAY change the request Note: For historic reasons, user agents MAY change the request
method from POST to GET for the subsequent request. If this method from POST to GET for the subsequent request. If this
behavior is undesired, status code 307 (Temporary Redirect) can be behavior is undesired, status code 307 (Temporary Redirect) can be
used instead. used instead.
7.3.3. 302 Found 4.5.3. 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. A response payload can contain a short hypertext note with response. A response payload can contain a short hypertext note with
a hyperlink to the new URI(s). a hyperlink to the new URI(s).
Note: For historic reasons, user agents MAY change the request Note: For historic reasons, user agents MAY change the request
method from POST to GET for the subsequent request. If this method from POST to GET for the subsequent request. If this
behavior is undesired, status code 307 (Temporary Redirect) can be behavior is undesired, status code 307 (Temporary Redirect) can be
used instead. used instead.
7.3.4. 303 See Other 4.5.4. 303 See Other
The 303 status code indicates that the server is redirecting the user The 303 status code indicates that the server is redirecting the user
agent to a different resource, as indicated by a URI in the Location agent to a different resource, as indicated by a URI in the Location
header field, that is intended to provide an indirect response to the header field, that is intended to provide an indirect response to the
original request. In order to satisfy the original request, a user original request. In order to satisfy the original request, a user
agent SHOULD perform a retrieval request using the Location URI (a agent SHOULD perform a retrieval request using the Location URI (a
GET or HEAD request if using HTTP), which may itself be redirected GET or HEAD request if using HTTP), which can itself be redirected
further, and present the eventual result as an answer to the original 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 request. Note that the new URI in the Location header field is not
considered equivalent to the effective request URI. considered equivalent to the effective request URI.
This status code is generally applicable to any HTTP method. It is This status code is generally applicable to any HTTP method. It is
primarily used to allow the output of a POST action to redirect the primarily used to allow the output of a POST action to redirect 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.
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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.
7.3.5. 305 Use Proxy 4.5.5. 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 C), and is now deprecated.
7.3.6. 306 (Unused) 4.5.6. 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.
7.3.7. 307 Temporary Redirect 4.5.7. 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. A response payload can contain a short hypertext note with response. A response payload can contain a short hypertext note with
a hyperlink to the new URI(s). a hyperlink to the new URI(s).
Note: This status code is similar to 302 Found, except that it Note: This status code is similar to 302 (Found), except that it
does not allow rewriting the request method from POST to GET. does not allow rewriting the request method from POST to GET.
This specification defines no equivalent counterpart for 301 Moved This specification defines no equivalent counterpart for 301
Permanently. (Moved Permanently) ([draft-reschke-http-status-308], however,
defines the status code 308 (Permanent Redirect) for this
purpose).
7.4. Client Error 4xx 4.6. 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.
7.4.1. 400 Bad Request 4.6.1. 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).
7.4.2. 402 Payment Required 4.6.2. 402 Payment Required
This code is reserved for future use. This code is reserved for future use.
7.4.3. 403 Forbidden 4.6.3. 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.
7.4.4. 404 Not Found 4.6.4. 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.
7.4.5. 405 Method Not Allowed 4.6.5. 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.
7.4.6. 406 Not Acceptable 4.6.6. 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.
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. Depending upon the format and the choose the one most appropriate. Depending upon the format and the
capabilities of the user agent, selection of the most appropriate capabilities of the user agent, selection of the most appropriate
choice MAY be performed automatically. However, this specification choice MAY be performed automatically. However, this specification
does not define any standard for such automatic selection. does not define any standard for such automatic selection.
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.
7.4.7. 408 Request Timeout 4.6.7. 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.
7.4.8. 409 Conflict 4.6.8. 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. differences between the two versions.
7.4.9. 410 Gone 4.6.9. 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
maintenance by notifying the recipient that the resource is maintenance by notifying the recipient that the resource is
intentionally unavailable and that the server owners desire that intentionally unavailable and that the server owners desire that
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 4.1.2 of [Part6]) to
determine freshness for 410 responses. determine freshness for 410 responses.
7.4.10. 411 Length Required 4.6.10. 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.
7.4.11. 413 Request Representation Too Large 4.6.11. 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.
7.4.12. 414 URI Too Long 4.6.12. 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 request-target. buffers for reading or manipulating the request-target.
7.4.13. 415 Unsupported Media Type 4.6.13. 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.
7.4.14. 417 Expectation Failed 4.6.14. 417 Expectation Failed
The expectation given in an Expect header field (see Section 10.3) The expectation given in an Expect header field (see Section 9.11)
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.
7.4.15. 426 Upgrade Required 4.6.15. 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 6.5 of This response MUST include an Upgrade header field (Section 6.5 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/3.0 Upgrade: HTTP/3.0
Connection: Upgrade Connection: Upgrade
Content-Length: 53 Content-Length: 53
Content-Type: text/plain Content-Type: text/plain
This service requires use of the HTTP/3.0 protocol. This service requires use of the HTTP/3.0 protocol.
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 might be available to the
user.
7.5. Server Error 5xx 4.7. 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.
7.5.1. 500 Internal Server Error 4.7.1. 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.
7.5.2. 501 Not Implemented 4.7.2. 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.
7.5.3. 502 Bad Gateway 4.7.3. 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.
7.5.4. 503 Service Unavailable 4.7.4. 503 Service Unavailable
The server is currently unable to handle the request due to a The server is currently unable to handle the request due to a
temporary overloading or maintenance of the server. temporary overloading or maintenance of the server.
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 10.8). If no be indicated in a Retry-After header field (Section 9.16). 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 (Internal Server Error) 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 has to use it when becoming overloaded. Some servers might
wish to simply refuse the connection. wish to simply refuse the connection.
7.5.5. 504 Gateway Timeout 4.7.5. 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 implementers: some deployed proxies are known to return
400 or 500 when DNS lookups time out. 400 (Bad Request) or 500 (Internal Server Error) when DNS lookups
time out.
7.5.6. 505 HTTP Version Not Supported 4.7.6. 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 2.7 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 5. Protocol Parameters
5.1. Date/Time Formats
HTTP applications have historically allowed three different formats HTTP applications have historically allowed three different formats
for date/time stamps. However, the preferred format is a fixed- for date/time stamps. However, the preferred format is a fixed-
length subset of that defined by [RFC1123]: length subset of that defined by [RFC1123]:
Sun, 06 Nov 1994 08:49:37 GMT ; RFC 1123 Sun, 06 Nov 1994 08:49:37 GMT ; RFC 1123
The other formats are described here only for compatibility with The other formats are described here only for compatibility with
obsolete implementations. obsolete implementations.
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Note: Recipients of date values are encouraged to be robust in Note: Recipients of date values are encouraged to be robust in
accepting date values that might have been sent by non-HTTP accepting date values that might have been sent by non-HTTP
applications, as is sometimes the case when retrieving or posting applications, as is sometimes the case when retrieving or posting
messages via proxies/gateways to SMTP or NNTP. messages via proxies/gateways to SMTP or NNTP.
Note: HTTP requirements for the date/time stamp format apply only Note: HTTP requirements for the date/time stamp format apply only
to their usage within the protocol stream. Clients and servers to their usage within the protocol stream. Clients and servers
are not required to use these formats for user presentation, are not required to use these formats for user presentation,
request logging, etc. request logging, etc.
9. Product Tokens 5.2. Product Tokens
Product tokens are used to allow communicating applications to Product tokens are used to allow communicating applications to
identify themselves by software name and version. Most fields using identify themselves by software name and version. Most fields using
product tokens also allow sub-products which form a significant part product tokens also allow sub-products which form a significant part
of the application to be listed, separated by whitespace. By of the application to be listed, separated by whitespace. By
convention, the products are listed in order of their significance convention, the products are listed in order of their significance
for identifying the application. for identifying the application.
product = token ["/" product-version] product = token ["/" product-version]
product-version = token product-version = token
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User-Agent: CERN-LineMode/2.15 libwww/2.17b3 User-Agent: CERN-LineMode/2.15 libwww/2.17b3
Server: Apache/0.8.4 Server: Apache/0.8.4
Product tokens SHOULD be short and to the point. They MUST NOT be Product tokens SHOULD be short and to the point. They MUST NOT be
used for advertising or other non-essential information. Although used for advertising or other non-essential information. Although
any token octet MAY appear in a product-version, this token SHOULD any token octet MAY appear in a product-version, this token SHOULD
only be used for a version identifier (i.e., successive versions of only be used for a version identifier (i.e., successive versions of
the same product SHOULD only differ in the product-version portion of the same product SHOULD only differ in the product-version portion of
the product value). the product value).
10. Header Field Definitions 5.3. Character Encodings (charset)
HTTP uses charset names to indicate the character encoding of a
textual representation.
A character encoding is identified by a case-insensitive token. The
complete set of tokens is defined by the IANA Character Set registry
(<http://www.iana.org/assignments/character-sets>).
charset = token
Although HTTP allows an arbitrary token to be used as a charset
value, any token that has a predefined value within the IANA
Character Set registry MUST represent the character encoding defined
by that registry. Applications SHOULD limit their use of character
encodings to those defined within the IANA registry.
HTTP uses charset in two contexts: within an Accept-Charset request
header field (in which the charset value is an unquoted token) and as
the value of a parameter in a Content-Type header field (within a
request or response), in which case the parameter value of the
charset parameter can be quoted.
Implementers need to be aware of IETF character set requirements
[RFC3629] [RFC2277].
5.4. Content Codings
Content coding values indicate an encoding transformation that has
been or can be applied to a representation. Content codings are
primarily used to allow a representation to be compressed or
otherwise usefully transformed without losing the identity of its
underlying media type and without loss of information. Frequently,
the representation is stored in coded form, transmitted directly, and
only decoded by the recipient.
content-coding = token
All content-coding values are case-insensitive. HTTP/1.1 uses
content-coding values in the Accept-Encoding (Section 9.3) and
Content-Encoding (Section 9.6) header fields. Although the value
describes the content-coding, what is more important is that it
indicates what decoding mechanism will be required to remove the
encoding.
compress
See Section 4.2.1 of [Part1].
deflate
See Section 4.2.2 of [Part1].
gzip
See Section 4.2.3 of [Part1].
5.4.1. Content Coding Registry
The HTTP Content Coding Registry defines the name space for the
content coding names.
Registrations MUST include the following fields:
o Name
o Description
o Pointer to specification text
Names of content codings MUST NOT overlap with names of transfer
codings (Section 4 of [Part1]), unless the encoding transformation is
identical (as is the case for the compression codings defined in
Section 4.2 of [Part1]).
Values to be added to this name space require IETF Review (see
Section 4.1 of [RFC5226]), and MUST conform to the purpose of content
coding defined in this section.
The registry itself is maintained at
<http://www.iana.org/assignments/http-parameters>.
5.5. Media Types
HTTP uses Internet Media Types [RFC2046] in the Content-Type
(Section 9.9) and Accept (Section 9.1) header fields in order to
provide open and extensible data typing and type negotiation.
media-type = type "/" subtype *( OWS ";" OWS parameter )
type = token
subtype = token
The type/subtype MAY be followed by parameters in the form of
attribute/value pairs.
parameter = attribute "=" value
attribute = token
value = word
The type, subtype, and parameter attribute names are case-
insensitive. Parameter values might or might not be case-sensitive,
depending on the semantics of the parameter name. The presence or
absence of a parameter might be significant to the processing of a
media-type, depending on its definition within the media type
registry.
A parameter value that matches the token production can be
transmitted as either a token or within a quoted-string. The quoted
and unquoted values are equivalent.
Note that some older HTTP applications do not recognize media type
parameters. When sending data to older HTTP applications,
implementations SHOULD only use media type parameters when they are
required by that type/subtype definition.
Media-type values are registered with the Internet Assigned Number
Authority (IANA). The media type registration process is outlined in
[RFC4288]. Use of non-registered media types is discouraged.
5.5.1. Canonicalization and Text Defaults
Internet media types are registered with a canonical form. A
representation transferred via HTTP messages MUST be in the
appropriate canonical form prior to its transmission except for
"text" types, as defined in the next paragraph.
When in canonical form, media subtypes of the "text" type use CRLF as
the text line break. HTTP relaxes this requirement and allows the
transport of text media with plain CR or LF alone representing a line
break when it is done consistently for an entire representation.
HTTP applications MUST accept CRLF, bare CR, and bare LF as
indicating a line break in text media received via HTTP. In
addition, if the text is in a character encoding that does not use
octets 13 and 10 for CR and LF respectively, as is the case for some
multi-byte character encodings, HTTP allows the use of whatever octet
sequences are defined by that character encoding to represent the
equivalent of CR and LF for line breaks. This flexibility regarding
line breaks applies only to text media in the payload body; a bare CR
or LF MUST NOT be substituted for CRLF within any of the HTTP control
structures (such as header fields and multipart boundaries).
If a representation is encoded with a content-coding, the underlying
data MUST be in a form defined above prior to being encoded.
5.5.2. Multipart Types
MIME provides for a number of "multipart" types -- encapsulations of
one or more representations within a single message body. All
multipart types share a common syntax, as defined in Section 5.1.1 of
[RFC2046], and MUST include a boundary parameter as part of the media
type value. The message body is itself a protocol element and MUST
therefore use only CRLF to represent line breaks between body-parts.
In general, HTTP treats a multipart message body no differently than
any other media type: strictly as payload. HTTP does not use the
multipart boundary as an indicator of message body length. In all
other respects, an HTTP user agent SHOULD follow the same or similar
behavior as a MIME user agent would upon receipt of a multipart type.
The MIME header fields within each body-part of a multipart message
body do not have any significance to HTTP beyond that defined by
their MIME semantics.
If an application receives an unrecognized multipart subtype, the
application MUST treat it as being equivalent to "multipart/mixed".
Note: The "multipart/form-data" type has been specifically defined
for carrying form data suitable for processing via the POST
request method, as described in [RFC2388].
5.6. Language Tags
A language tag, as defined in [RFC5646], identifies a natural
language spoken, written, or otherwise conveyed by human beings for
communication of information to other human beings. Computer
languages are explicitly excluded. HTTP uses language tags within
the Accept-Language and Content-Language fields.
In summary, a language tag is composed of one or more parts: A
primary language subtag followed by a possibly empty series of
subtags:
language-tag = <Language-Tag, defined in [RFC5646], Section 2.1>
White space is not allowed within the tag and all tags are case-
insensitive. The name space of language subtags is administered by
the IANA (see
<http://www.iana.org/assignments/language-subtag-registry>).
Example tags include:
en, en-US, es-419, az-Arab, x-pig-latin, man-Nkoo-GN
See [RFC5646] for further information.
6. Payload
HTTP messages MAY transfer a payload if not otherwise restricted by
the request method or response status code. The payload consists of
metadata, in the form of header fields, and data, in the form of the
sequence of octets in the message body after any transfer-coding has
been decoded.
A "payload" in HTTP is always a partial or complete representation of
some resource. We use separate terms for payload and representation
because some messages contain only the associated representation's
header fields (e.g., responses to HEAD) or only some part(s) of the
representation (e.g., the 206 (Partial Content) status code).
6.1. Payload Header Fields
HTTP header fields that specifically define the payload, rather than
the associated representation, are referred to as "payload header
fields". The following payload header fields are defined by
HTTP/1.1:
+-------------------+--------------------------+
| Header Field Name | Defined in... |
+-------------------+--------------------------+
| Content-Length | Section 3.3.2 of [Part1] |
| Content-Range | Section 5.2 of [Part5] |
+-------------------+--------------------------+
6.2. Payload Body
A payload body is only present in a message when a message body is
present, as described in Section 3.3 of [Part1]. The payload body is
obtained from the message body by decoding any Transfer-Encoding that
might have been applied to ensure safe and proper transfer of the
message.
7. Representation
A "representation" is information in a format that can be readily
communicated from one party to another. A resource representation is
information that reflects the state of that resource, as observed at
some point in the past (e.g., in a response to GET) or to be desired
at some point in the future (e.g., in a PUT request).
Most, but not all, representations transferred via HTTP are intended
to be a representation of the target resource (the resource
identified by the effective request URI). The precise semantics of a
representation are determined by the type of message (request or
response), the request method, the response status code, and the
representation metadata. For example, the above semantic is true for
the representation in any 200 (OK) response to GET and for the
representation in any PUT request. A 200 response to PUT, in
contrast, contains either a representation that describes the
successful action or a representation of the target resource, with
the latter indicated by a Content-Location header field with the same
value as the effective request URI. Likewise, response messages with
an error status code usually contain a representation that describes
the error and what next steps are suggested for resolving it.
Request and Response messages MAY transfer a representation if not
otherwise restricted by the request method or response status code.
A representation consists of metadata (representation header fields)
and data (representation body). When a complete or partial
representation is enclosed in an HTTP message, it is referred to as
the payload of the 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
representation body is obtained from the message body by decoding any
Transfer-Encoding that might have been applied to ensure safe and
proper transfer of the message.
7.1. Identifying the Resource Associated with a Representation
It is sometimes necessary to determine an identifier for the resource
associated with a representation.
An HTTP request representation, when present, is always associated
with an anonymous (i.e., unidentified) resource.
In the common case, an HTTP response is a representation of the
target resource (see Section 5.5 of [Part1]). However, this is not
always the case. To determine the URI of the resource a response is
associated with, the following rules are used (with the first
applicable one being selected):
1. If the response status code is 200 (OK) or 203 (Non-Authoritative
Information) and the request method was GET, the response payload
is a representation of the target resource.
2. If the response status code is 204 (No Content), 206 (Partial
Content), or 304 (Not Modified) and the request method was GET or
HEAD, the response payload is a partial representation of the
target resource.
3. If the response has a Content-Location header field, and that URI
is the same as the effective request URI, the response payload is
a representation of the target resource.
4. If the response has a Content-Location header field, and that URI
is not the same as the effective request URI, then the response
asserts that its payload is a representation of the resource
identified by the Content-Location URI. However, such an
assertion cannot be trusted unless it can be verified by other
means (not defined by HTTP).
5. Otherwise, the response is a representation of an anonymous
(i.e., unidentified) resource.
[[TODO-req-uri: The comparison function is going to have to be
defined somewhere, because we already need to compare URIs for things
like cache invalidation.]]
7.2. Representation Header Fields
Representation header fields define metadata about the representation
data enclosed in the message body or, if no message body is present,
about the representation that would have been transferred in a 200
(OK) response to a simultaneous GET request with the same effective
request URI.
The following header fields are defined as representation metadata:
+-------------------+------------------------+
| Header Field Name | Defined in... |
+-------------------+------------------------+
| Content-Encoding | Section 9.6 |
| Content-Language | Section 9.7 |
| Content-Location | Section 9.8 |
| Content-Type | Section 9.9 |
| Expires | Section 7.3 of [Part6] |
+-------------------+------------------------+
We use the term "selected representation" to refer to the the current
representation of a target resource that would have been selected in
a successful response if the same request had used the method GET and
excluded any conditional request header fields.
Additional header fields define metadata about the selected
representation, which might differ from the representation included
in the message for responses to some state-changing methods. The
following header fields are defined as selected representation
metadata:
+-------------------+------------------------+
| Header Field Name | Defined in... |
+-------------------+------------------------+
| ETag | Section 2.3 of [Part4] |
| Last-Modified | Section 2.2 of [Part4] |
+-------------------+------------------------+
7.3. Representation Data
The representation body associated with an HTTP message is either
provided as the payload body of the message or referred to by the
message semantics and the effective request URI. The representation
data is in a format and encoding defined by the representation
metadata header fields.
The data type of the representation data is determined via the header
fields Content-Type and Content-Encoding. These define a two-layer,
ordered encoding model:
representation-data := Content-Encoding( Content-Type( bits ) )
Content-Type specifies the media type of the underlying data, which
defines both the data format and how that data SHOULD be processed by
the recipient (within the scope of the request method semantics).
Any HTTP/1.1 message containing a payload body SHOULD include a
Content-Type header field defining the media type of the associated
representation unless that metadata is unknown to the sender. If the
Content-Type header field is not present, it indicates that the
sender does not know the media type of the representation; recipients
MAY either assume that the media type is "application/octet-stream"
([RFC2046], Section 4.5.1) or examine the content to determine its
type.
In practice, resource owners do not always properly configure their
origin server to provide the correct Content-Type for a given
representation, with the result that some clients will examine a
response body's content and override the specified type. Clients
that do so risk drawing incorrect conclusions, which might expose
additional security risks (e.g., "privilege escalation").
Furthermore, it is impossible to determine the sender's intent by
examining the data format: many data formats match multiple media
types that differ only in processing semantics. Implementers are
encouraged to provide a means of disabling such "content sniffing"
when it is used.
Content-Encoding is used to indicate any additional content codings
applied to the data, usually for the purpose of data compression,
that are a property of the representation. If Content-Encoding is
not present, then there is no additional encoding beyond that defined
by the Content-Type header field.
8. Content Negotiation
HTTP responses include a representation which contains information
for interpretation, whether by a human user or for further
processing. Often, the server has different ways of representing the
same information; for example, in different formats, languages, or
using different character encodings.
HTTP clients and their users might have different or variable
capabilities, characteristics or preferences which would influence
which representation, among those available from the server, would be
best for the server to deliver. For this reason, HTTP provides
mechanisms for "content negotiation" -- a process of allowing
selection of a representation of a given resource, when more than one
is available.
This specification defines two patterns of content negotiation;
"server-driven", where the server selects the representation based
upon the client's stated preferences, and "agent-driven" negotiation,
where the server provides a list of representations for the client to
choose from, based upon their metadata. In addition, there are other
patterns: some applications use an "active content" pattern, where
the server returns active content which runs on the client and, based
on client available parameters, selects additional resources to
invoke. "Transparent Content Negotiation" ([RFC2295]) has also been
proposed.
These patterns are all widely used, and have trade-offs in
applicability and practicality. In particular, when the number of
preferences or capabilities to be expressed by a client are large
(such as when many different formats are supported by a user-agent),
server-driven negotiation becomes unwieldy, and might not be
appropriate. Conversely, when the number of representations to
choose from is very large, agent-driven negotiation might not be
appropriate.
Note that in all cases, the supplier of representations has the
responsibility for determining which representations might be
considered to be the "same information".
8.1. Server-driven Negotiation
If the selection of the best representation for a response is made by
an algorithm located at the server, it is called server-driven
negotiation. Selection is based on the available representations of
the response (the dimensions over which it can vary; e.g., language,
content-coding, etc.) and the contents of particular header fields in
the request message or on other information pertaining to the request
(such as the network address of the client).
Server-driven negotiation is advantageous when the algorithm for
selecting from among the available representations is difficult to
describe to the user agent, or when the server desires to send its
"best guess" to the client along with the first response (hoping to
avoid the round-trip delay of a subsequent request if the "best
guess" is good enough for the user). In order to improve the
server's guess, the user agent MAY include request header fields
(Accept, Accept-Language, Accept-Encoding, etc.) which describe its
preferences for such a response.
Server-driven negotiation has disadvantages:
1. It is impossible for the server to accurately determine what
might be "best" for any given user, since that would require
complete knowledge of both the capabilities of the user agent and
the intended use for the response (e.g., does the user want to
view it on screen or print it on paper?).
2. Having the user agent describe its capabilities in every request
can be both very inefficient (given that only a small percentage
of responses have multiple representations) and a potential
violation of the user's privacy.
3. It complicates the implementation of an origin server and the
algorithms for generating responses to a request.
4. It might limit a public cache's ability to use the same response
for multiple user's requests.
Server-driven negotiation allows the user agent to specify its
preferences, but it cannot expect responses to always honor them.
For example, the origin server might not implement server-driven
negotiation, or it might decide that sending a response that doesn't
conform to them is better than sending a 406 (Not Acceptable)
response.
Many of the mechanisms for expressing preferences use quality values
to declare relative preference. See Section 4.3.1 of [Part1] for
more information.
HTTP/1.1 includes the following header fields for enabling server-
driven negotiation through description of user agent capabilities and
user preferences: Accept (Section 9.1), Accept-Charset (Section 9.2),
Accept-Encoding (Section 9.3), Accept-Language (Section 9.4), and
User-Agent (Section 9.18). However, an origin server is not limited
to these dimensions and MAY vary the response based on any aspect of
the request, including aspects of the connection (e.g., IP address)
or information within extension header fields not defined by this
specification.
Note: In practice, User-Agent based negotiation is fragile,
because new clients might not be recognized.
The Vary header field (Section 7.5 of [Part6]) can be used to express
the parameters the server uses to select a representation that is
subject to server-driven negotiation.
8.2. Agent-driven Negotiation
With agent-driven negotiation, selection of the best representation
for a response is performed by the user agent after receiving an
initial response from the origin server. Selection is based on a
list of the available representations of the response included within
the header fields or body of the initial response, with each
representation identified by its own URI. Selection from among the
representations can be performed automatically (if the user agent is
capable of doing so) or manually by the user selecting from a
generated (possibly hypertext) menu.
Agent-driven negotiation is advantageous when the response would vary
over commonly-used dimensions (such as type, language, or encoding),
when the origin server is unable to determine a user agent's
capabilities from examining the request, and generally when public
caches are used to distribute server load and reduce network usage.
Agent-driven negotiation suffers from the disadvantage of needing a
second request to obtain the best alternate representation. This
second request is only efficient when caching is used. In addition,
this specification does not define any mechanism for supporting
automatic selection, though it also does not prevent any such
mechanism from being developed as an extension and used within
HTTP/1.1.
This specification defines the 300 (Multiple Choices) and 406 (Not
Acceptable) status codes for enabling agent-driven negotiation when
the server is unwilling or unable to provide a varying response using
server-driven negotiation.
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 and to the payload
of messages.
10.1. Allow 9.1. Accept
The "Accept" header field can be used by user agents to specify
response media types that are acceptable. Accept header fields can
be used to indicate that the request is specifically limited to a
small set of desired types, as in the case of a request for an in-
line image.
Accept = #( media-range [ accept-params ] )
media-range = ( "*/*"
/ ( type "/" "*" )
/ ( type "/" subtype )
) *( OWS ";" OWS parameter )
accept-params = OWS ";" OWS "q=" qvalue *( accept-ext )
accept-ext = OWS ";" OWS token [ "=" word ]
The asterisk "*" character is used to group media types into ranges,
with "*/*" indicating all media types and "type/*" indicating all
subtypes of that type. The media-range MAY include media type
parameters that are applicable to that range.
Each media-range MAY be followed by one or more accept-params,
beginning with the "q" parameter for indicating a relative quality
factor. The first "q" parameter (if any) separates the media-range
parameter(s) from the accept-params. Quality factors allow the user
or user agent to indicate the relative degree of preference for that
media-range, using the qvalue scale from 0 to 1 (Section 4.3.1 of
[Part1]). The default value is q=1.
Note: Use of the "q" parameter name to separate media type
parameters from Accept extension parameters is due to historical
practice. Although this prevents any media type parameter named
"q" from being used with a media range, such an event is believed
to be unlikely given the lack of any "q" parameters in the IANA
media type registry and the rare usage of any media type
parameters in Accept. Future media types are discouraged from
registering any parameter named "q".
The example
Accept: audio/*; q=0.2, audio/basic
SHOULD be interpreted as "I prefer audio/basic, but send me any audio
type if it is the best available after an 80% mark-down in quality".
A request without any Accept header field implies that the user agent
will accept any media type in response. If an Accept header field is
present in a request and none of the available representations for
the response have a media type that is listed as acceptable, the
origin server MAY either honor the Accept header field by sending a
406 (Not Acceptable) response or disregard the Accept header field by
treating the response as if it is not subject to content negotiation.
A more elaborate example is
Accept: text/plain; q=0.5, text/html,
text/x-dvi; q=0.8, text/x-c
Verbally, this would be interpreted as "text/html and text/x-c are
the preferred media types, but if they do not exist, then send the
text/x-dvi representation, and if that does not exist, send the text/
plain representation".
Media ranges can be overridden by more specific media ranges or
specific media types. If more than one media range applies to a
given type, the most specific reference has precedence. For example,
Accept: text/*, text/plain, text/plain;format=flowed, */*
have the following precedence:
1. text/plain;format=flowed
2. text/plain
3. text/*
4. */*
The media type quality factor associated with a given type is
determined by finding the media range with the highest precedence
which matches that type. For example,
Accept: text/*;q=0.3, text/html;q=0.7, text/html;level=1,
text/html;level=2;q=0.4, */*;q=0.5
would cause the following values to be associated:
+-------------------+---------------+
| Media Type | Quality Value |
+-------------------+---------------+
| text/html;level=1 | 1 |
| text/html | 0.7 |
| text/plain | 0.3 |
| image/jpeg | 0.5 |
| text/html;level=2 | 0.4 |
| text/html;level=3 | 0.7 |
+-------------------+---------------+
Note: A user agent might be provided with a default set of quality
values for certain media ranges. However, unless the user agent is a
closed system which cannot interact with other rendering agents, this
default set ought to be configurable by the user.
9.2. Accept-Charset
The "Accept-Charset" header field can be used by user agents to
indicate what character encodings are acceptable in a response
payload. This field allows clients capable of understanding more
comprehensive or special-purpose character encodings to signal that
capability to a server which is capable of representing documents in
those character encodings.
Accept-Charset = 1#( ( charset / "*" )
[ OWS ";" OWS "q=" qvalue ] )
Character encoding values (a.k.a., charsets) are described in
Section 5.3. Each charset MAY be given an associated quality value
which represents the user's preference for that charset. The default
value is q=1. An example is
Accept-Charset: iso-8859-5, unicode-1-1;q=0.8
The special value "*", if present in the Accept-Charset field,
matches every character encoding which is not mentioned elsewhere in
the Accept-Charset field. If no "*" is present in an Accept-Charset
field, then all character encodings not explicitly mentioned get a
quality value of 0.
A request without any Accept-Charset header field implies that the
user agent will accept any character encoding in response. If an
Accept-Charset header field is present in a request and none of the
available representations for the response have a character encoding
that is listed as acceptable, the origin server MAY either honor the
Accept-Charset header field by sending a 406 (Not Acceptable)
response or disregard the Accept-Charset header field by treating the
response as if it is not subject to content negotiation.
9.3. Accept-Encoding
The "Accept-Encoding" header field can be used by user agents to
indicate what response content-codings (Section 5.4) are acceptable
in the response. An "identity" token is used as a synonym for "no
encoding" in order to communicate when no encoding is preferred.
Accept-Encoding = #( codings [ OWS ";" OWS "q=" qvalue ] )
codings = content-coding / "identity" / "*"
Each codings value MAY be given an associated quality value which
represents the preference for that encoding. The default value is
q=1.
For example,
Accept-Encoding: compress, gzip
Accept-Encoding:
Accept-Encoding: *
Accept-Encoding: compress;q=0.5, gzip;q=1.0
Accept-Encoding: gzip;q=1.0, identity; q=0.5, *;q=0
A server tests whether a content-coding for a given representation is
acceptable, according to an Accept-Encoding field, using these rules:
1. The special "*" symbol in an Accept-Encoding field matches any
available content-coding not explicitly listed in the header
field.
2. If the representation has no content-coding, then it is
acceptable by default unless specifically excluded by the Accept-
Encoding field stating either "identity;q=0" or "*;q=0" without a
more specific entry for "identity".
3. If the representation's content-coding is one of the content-
codings listed in the Accept-Encoding field, then it is
acceptable unless it is accompanied by a qvalue of 0. (As
defined in Section 4.3.1 of [Part1], a qvalue of 0 means "not
acceptable".)
4. If multiple content-codings are acceptable, then the acceptable
content-coding with the highest non-zero qvalue is preferred.
An Accept-Encoding header field with a combined field-value that is
empty implies that the user agent does not want any content-coding in
response. If an Accept-Encoding header field is present in a request
and none of the available representations for the response have a
content-coding that is listed as acceptable, the origin server SHOULD
send a response without any content-coding.
A request without an Accept-Encoding header field implies that the
user agent will accept any content-coding in response, but a
representation without content-coding is preferred for compatibility
with the widest variety of user agents.
Note: Most HTTP/1.0 applications do not recognize or obey qvalues
associated with content-codings. This means that qvalues will not
work and are not permitted with x-gzip or x-compress.
9.4. Accept-Language
The "Accept-Language" header field can be used by user agents to
indicate the set of natural languages that are preferred in the
response. Language tags are defined in Section 5.6.
Accept-Language =
1#( language-range [ OWS ";" OWS "q=" qvalue ] )
language-range =
<language-range, defined in [RFC4647], Section 2.1>
Each language-range can be given an associated quality value which
represents an estimate of the user's preference for the languages
specified by that range. The quality value defaults to "q=1". For
example,
Accept-Language: da, en-gb;q=0.8, en;q=0.7
would mean: "I prefer Danish, but will accept British English and
other types of English". (see also Section 2.3 of [RFC4647])
For matching, Section 3 of [RFC4647] defines several matching
schemes. Implementations can offer the most appropriate matching
scheme for their requirements.
Note: The "Basic Filtering" scheme ([RFC4647], Section 3.3.1) is
identical to the matching scheme that was previously defined in
Section 14.4 of [RFC2616].
It might be contrary to the privacy expectations of the user to send
an Accept-Language header field with the complete linguistic
preferences of the user in every request. For a discussion of this
issue, see Section 11.5.
As intelligibility is highly dependent on the individual user, it is
recommended that client applications make the choice of linguistic
preference available to the user. If the choice is not made
available, then the Accept-Language header field MUST NOT be given in
the request.
Note: When making the choice of linguistic preference available to
the user, we remind implementers of the fact that users are not
familiar with the details of language matching as described above,
and ought to be provided appropriate guidance. As an example,
users might assume that on selecting "en-gb", they will be served
any kind of English document if British English is not available.
A user agent might suggest in such a case to add "en" to get the
best matching behavior.
9.5. 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
with the resource. with the resource.
Allow = #method Allow = #method
Example of use: Example of use:
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.
10.2. Date 9.6. Content-Encoding
The "Content-Encoding" header field indicates what content-codings
have been applied to the representation beyond those inherent in the
media type, and thus what decoding mechanisms have to be applied in
order to obtain the media-type referenced by the Content-Type header
field. Content-Encoding is primarily used to allow a representation
to be compressed without losing the identity of its underlying media
type.
Content-Encoding = 1#content-coding
Content codings are defined in Section 5.4. An example of its use is
Content-Encoding: gzip
The content-coding is a characteristic of the representation.
Typically, the representation body is stored with this encoding and
is only decoded before rendering or analogous usage. However, a
transforming proxy MAY modify the content-coding if the new coding is
known to be acceptable to the recipient, unless the "no-transform"
cache-control directive is present in the message.
If the media type includes an inherent encoding, such as a data
format that is always compressed, then that encoding would not be
restated as a Content-Encoding even if it happens to be the same
algorithm as one of the content-codings. Such a content-coding would
only be listed if, for some bizarre reason, it is applied a second
time to form the representation. Likewise, an origin server might
choose to publish the same payload data as multiple representations
that differ only in whether the coding is defined as part of Content-
Type or Content-Encoding, since some user agents will behave
differently in their handling of each response (e.g., open a "Save as
..." dialog instead of automatic decompression and rendering of
content).
A representation that has a content-coding applied to it MUST include
a Content-Encoding header field that lists the content-coding(s)
applied.
If multiple encodings have been applied to a representation, the
content codings MUST be listed in the order in which they were
applied. Additional information about the encoding parameters MAY be
provided by other header fields not defined by this specification.
If the content-coding of a representation in a request message is not
acceptable to the origin server, the server SHOULD respond with a
status code of 415 (Unsupported Media Type).
9.7. Content-Language
The "Content-Language" header field describes the natural language(s)
of the intended audience for the representation. Note that this
might not be equivalent to all the languages used within the
representation.
Content-Language = 1#language-tag
Language tags are defined in Section 5.6. The primary purpose of
Content-Language is to allow a user to identify and differentiate
representations according to the user's own preferred language.
Thus, if the body content is intended only for a Danish-literate
audience, the appropriate field is
Content-Language: da
If no Content-Language is specified, the default is that the content
is intended for all language audiences. This might mean that the
sender does not consider it to be specific to any natural language,
or that the sender does not know for which language it is intended.
Multiple languages MAY be listed for content that is intended for
multiple audiences. For example, a rendition of the "Treaty of
Waitangi", presented simultaneously in the original Maori and English
versions, would call for
Content-Language: mi, en
However, just because multiple languages are present within a
representation does not mean that it is intended for multiple
linguistic audiences. An example would be a beginner's language
primer, such as "A First Lesson in Latin", which is clearly intended
to be used by an English-literate audience. In this case, the
Content-Language would properly only include "en".
Content-Language MAY be applied to any media type -- it is not
limited to textual documents.
9.8. Content-Location
The "Content-Location" header field supplies a URI that can be used
as a specific identifier for the representation in this message. In
other words, if one were to perform a GET on this URI at the time of
this message's generation, then a 200 (OK) response would contain the
same representation that is enclosed as payload in this message.
Content-Location = absolute-URI / partial-URI
The Content-Location value is not a replacement for the effective
Request URI (Section 5.5 of [Part1]). It is representation metadata.
It has the same syntax and semantics as the header field of the same
name defined for MIME body parts in Section 4 of [RFC2557]. However,
its appearance in an HTTP message has some special implications for
HTTP recipients.
If Content-Location is included in a response message and its value
is the same as the effective request URI, then the response payload
SHOULD be considered a current representation of that resource. For
a GET or HEAD request, this is the same as the default semantics when
no Content-Location is provided by the server. For a state-changing
request like PUT or POST, it implies that the server's response
contains the new representation of that resource, thereby
distinguishing it from representations that might only report about
the action (e.g., "It worked!"). This allows authoring applications
to update their local copies without the need for a subsequent GET
request.
If Content-Location is included in a response message and its value
differs from the effective request URI, then the origin server is
informing recipients that this representation has its own, presumably
more specific, identifier. For a GET or HEAD request, this is an
indication that the effective request URI identifies a resource that
is subject to content negotiation and the selected representation for
this response can also be found at the identified URI. For other
methods, such a Content-Location indicates that this representation
contains a report on the action's status and the same report is
available (for future access with GET) at the given URI. For
example, a purchase transaction made via a POST request might include
a receipt document as the payload of the 200 (OK) response; the
Content-Location value provides an identifier for retrieving a copy
of that same receipt in the future.
If Content-Location is included in a request message, then it MAY be
interpreted by the origin server as an indication of where the user
agent originally obtained the content of the enclosed representation
(prior to any subsequent modification of the content by that user
agent). In other words, the user agent is providing the same
representation metadata that it received with the original
representation. However, such interpretation MUST NOT be used to
alter the semantics of the method requested by the client. For
example, if a client makes a PUT request on a negotiated resource and
the origin server accepts that PUT (without redirection), then the
new set of values for that resource is expected to be consistent with
the one representation supplied in that PUT; the Content-Location
cannot be used as a form of reverse content selection that identifies
only one of the negotiated representations to be updated. If the
user agent had wanted the latter semantics, it would have applied the
PUT directly to the Content-Location URI.
A Content-Location field received in a request message is transitory
information that SHOULD NOT be saved with other representation
metadata for use in later responses. The Content-Location's value
might be saved for use in other contexts, such as within source links
or other metadata.
A cache cannot assume that a representation with a Content-Location
different from the URI used to retrieve it can be used to respond to
later requests on that Content-Location URI.
If the Content-Location value is a partial URI, the partial URI is
interpreted relative to the effective request URI.
9.9. Content-Type
The "Content-Type" header field indicates the media type of the
representation. In the case of responses to the HEAD method, the
media type is that which would have been sent had the request been a
GET.
Content-Type = media-type
Media types are defined in Section 5.5. An example of the field is
Content-Type: text/html; charset=ISO-8859-4
Further discussion of Content-Type is provided in Section 7.3.
9.10. Date
The "Date" header field represents the date and time at which the The "Date" header field represents the date and time at which the
message was originated, having the same semantics as the Origination message was originated, having the same semantics as the Origination
Date Field (orig-date) defined in Section 3.6.1 of [RFC5322]. The 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 field value is an HTTP-date, as defined in Section 5.1; it MUST be
in rfc1123-date format. sent in rfc1123-date format.
Date = HTTP-date Date = HTTP-date
An example is An example is
Date: Tue, 15 Nov 1994 08:12:31 GMT Date: Tue, 15 Nov 1994 08:12:31 GMT
Origin servers MUST include a Date header field in all responses, Origin servers MUST include a Date header field in all responses,
except in these cases: except in these cases:
skipping to change at page 43, line 31 skipping to change at page 62, line 21
The HTTP-date sent in a Date header field SHOULD NOT represent a date 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 and time subsequent to the generation of the message. It SHOULD
represent the best available approximation of the date and time of represent the best available approximation of the date and time of
message generation, unless the implementation has no means of message generation, unless the implementation has no means of
generating a reasonably accurate date and time. In theory, the date generating a reasonably accurate date and time. In theory, the date
ought to represent the moment just before the payload is generated. ought to represent the moment just before the payload is generated.
In practice, the date can be generated at any time during the message In practice, the date can be generated at any time during the message
origination without affecting its semantic value. origination without affecting its semantic value.
10.3. Expect 9.11. 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 = expect-name [ BWS "=" BWS expect-value ] expectation = expect-name [ BWS "=" BWS expect-value ]
*( OWS ";" [ OWS expect-param ] ) *( OWS ";" [ OWS expect-param ] )
expect-param = expect-name [ BWS "=" BWS expect-value ] expect-param = expect-name [ BWS "=" BWS expect-value ]
skipping to change at page 44, line 21 skipping to change at page 63, line 13
sensitive for values (expect-value). sensitive for values (expect-value).
The Expect mechanism is hop-by-hop: the above requirements apply to The Expect mechanism is hop-by-hop: the above requirements apply to
any server, including proxies. However, the Expect header field any server, including proxies. However, the Expect header field
itself is end-to-end; it MUST be forwarded if the request is itself is end-to-end; it MUST be forwarded if the request is
forwarded. 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.
10.4. From 9.12. 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>
skipping to change at page 45, line 7 skipping to change at page 63, line 48
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.
10.5. Location 9.13. Location
The "Location" header field MAY be sent in responses to refer to a The "Location" header field MAY be sent in responses to refer to a
specific resource in accordance with the semantics of the status specific resource in accordance with the semantics of the status
code. code.
Location = URI-reference Location = URI-reference
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 (Redirection)
location SHOULD indicate the server's preferred URI for automatic responses, the location SHOULD indicate the server's preferred URI
redirection to the resource. for automatic redirection to the resource.
The field value consists of a single URI-reference. When it has the The field value consists of a single URI-reference. When it has the
form of a relative reference ([RFC3986], Section 4.2), the final form of a relative reference ([RFC3986], Section 4.2), the final
value is computed by resolving it against the effective request URI value is computed by resolving it against the effective request URI
([RFC3986], Section 5). If the original URI, as navigated to by the ([RFC3986], Section 5). If the original URI, as navigated to by the
user agent, did contain a fragment identifier, and the final value user agent, did contain a fragment identifier, and the final value
does not, then the original URI's fragment identifier is added to the does not, then the original URI's fragment identifier is added to the
final value. final value.
For example, the original URI "http://www.example.org/~tim", combined For example, the original URI "http://www.example.org/~tim", combined
skipping to change at page 45, line 47 skipping to change at page 64, line 39
with a field value given as: with a field value given as:
Location: http://www.example.net/index.html Location: http://www.example.net/index.html
would result in a final value of would result in a final value of
"http://www.example.net/index.html#larry", preserving the original "http://www.example.net/index.html#larry", preserving the original
fragment identifier. fragment identifier.
Note: Some recipients attempt to recover from Location fields that Note: Some recipients attempt to recover from Location fields that
are not valid URI references. This specification does not mandate are not valid URI references. This specification does not mandate
or define such processing, but does allow it (see Section 1.1). or define such processing, but does allow it.
There are circumstances in which a fragment identifier in a Location There are circumstances in which a fragment identifier in a Location
URI would not be appropriate. For instance, when it appears in a 201 URI would not be appropriate. For instance, when it appears in a 201
Created response, where the Location header field specifies the URI (Created) response, where the Location header field specifies the URI
for the entire created resource. for the entire created resource.
Note: The Content-Location header field (Section 6.7 of [Part3]) Note: The Content-Location header field (Section 9.8) differs from
differs from Location in that the Content-Location identifies the Location in that the Content-Location identifies the most specific
most specific resource corresponding to the enclosed resource corresponding to the enclosed representation. It is
representation. It is therefore possible for a response to therefore possible for a response to contain header fields for
contain header fields for both Location and Content-Location. both Location and Content-Location.
10.6. Max-Forwards 9.14. 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 6.8) and OPTIONS (Section 6.2) methods to limit the number (Section 2.3.7) and OPTIONS (Section 2.3.1) methods to limit the
of times that the request is forwarded by proxies. This can be number of times that the request is forwarded by proxies. This can
useful when the client is attempting to trace a request which appears be useful when the client is attempting to trace a request which
to be failing or looping mid-chain. appears to be failing or looping 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.
10.7. Referer 9.15. 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 target URI was obtained (the of the resource from which the target URI was obtained (the
"referrer", although the header field is misspelled.). "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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URIs (e.g., FTP). URIs (e.g., FTP).
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 12.2 for security considerations. fragment. See Section 11.2 for security considerations.
10.8. Retry-After 9.16. 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 to wait before issuing the redirected request. user-agent is asked to 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.
skipping to change at page 47, line 43 skipping to change at page 66, line 34
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.
10.9. Server 9.17. 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 9) and The field can contain multiple product tokens (Section 5.2) and
comments (Section 3.2 of [Part1]) identifying the server and any comments (Section 3.2 of [Part1]) identifying the server and any
significant subproducts. The product tokens are listed in order of significant subproducts. The product tokens are listed in order of
their significance for identifying the application. 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 6.2 of [Part1]). MUST include a Via field (as described in Section 6.2 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 implementers are encouraged to make this field a configurable
option. option.
10.10. User-Agent 9.18. 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 9) and The field can contain multiple product tokens (Section 5.2) and
comments (Section 3.2 of [Part1]) identifying the agent and its comments (Section 3.2 of [Part1]) identifying the agent and its
significant subproducts. By convention, the product tokens are significant subproducts. By convention, the product tokens are
listed in order of their significance for identifying the 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 49, line 7 skipping to change at page 67, line 46
with them, as this circumvents the purpose of the field. Finally, with them, as this circumvents the purpose of the field. Finally,
they are encouraged not to use comments to identify products; doing they are encouraged not to use comments to identify products; doing
so makes the field value more difficult to parse. so makes the field value more difficult to parse.
User-Agent = product *( RWS ( product / comment ) ) User-Agent = product *( RWS ( product / comment ) )
Example: Example:
User-Agent: CERN-LineMode/2.15 libwww/2.17b3 User-Agent: CERN-LineMode/2.15 libwww/2.17b3
11. IANA Considerations 10. IANA Considerations
11.1. Method Registry 10.1. Method Registry
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 | Idempotent | Reference |
+---------+------+-------------+ +---------+------+------------+---------------+
| CONNECT | no | Section 6.9 | | CONNECT | no | no | Section 2.3.8 |
| DELETE | no | Section 6.7 | | DELETE | no | yes | Section 2.3.6 |
| GET | yes | Section 6.3 | | GET | yes | yes | Section 2.3.2 |
| HEAD | yes | Section 6.4 | | HEAD | yes | yes | Section 2.3.3 |
| OPTIONS | yes | Section 6.2 | | OPTIONS | yes | yes | Section 2.3.1 |
| POST | no | Section 6.5 | | POST | no | no | Section 2.3.4 |
| PUT | no | Section 6.6 | | PUT | no | yes | Section 2.3.5 |
| TRACE | yes | Section 6.8 | | TRACE | yes | yes | Section 2.3.7 |
+---------+------+-------------+ +---------+------+------------+---------------+
11.2. 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 7.1.1 | | 100 | Continue | Section 4.3.1 |
| 101 | Switching Protocols | Section 7.1.2 | | 101 | Switching Protocols | Section 4.3.2 |
| 200 | OK | Section 7.2.1 | | 200 | OK | Section 4.4.1 |
| 201 | Created | Section 7.2.2 | | 201 | Created | Section 4.4.2 |
| 202 | Accepted | Section 7.2.3 | | 202 | Accepted | Section 4.4.3 |
| 203 | Non-Authoritative Information | Section 7.2.4 | | 203 | Non-Authoritative Information | Section 4.4.4 |
| 204 | No Content | Section 7.2.5 | | 204 | No Content | Section 4.4.5 |
| 205 | Reset Content | Section 7.2.6 | | 205 | Reset Content | Section 4.4.6 |
| 300 | Multiple Choices | Section 7.3.1 | | 300 | Multiple Choices | Section 4.5.1 |
| 301 | Moved Permanently | Section 7.3.2 | | 301 | Moved Permanently | Section 4.5.2 |
| 302 | Found | Section 7.3.3 | | 302 | Found | Section 4.5.3 |
| 303 | See Other | Section 7.3.4 | | 303 | See Other | Section 4.5.4 |
| 305 | Use Proxy | Section 7.3.5 | | 305 | Use Proxy | Section 4.5.5 |
| 306 | (Unused) | Section 7.3.6 | | 306 | (Unused) | Section 4.5.6 |
| 307 | Temporary Redirect | Section 7.3.7 | | 307 | Temporary Redirect | Section 4.5.7 |
| 400 | Bad Request | Section 7.4.1 | | 400 | Bad Request | Section 4.6.1 |
| 402 | Payment Required | Section 7.4.2 | | 402 | Payment Required | Section 4.6.2 |
| 403 | Forbidden | Section 7.4.3 | | 403 | Forbidden | Section 4.6.3 |
| 404 | Not Found | Section 7.4.4 | | 404 | Not Found | Section 4.6.4 |
| 405 | Method Not Allowed | Section 7.4.5 | | 405 | Method Not Allowed | Section 4.6.5 |
| 406 | Not Acceptable | Section 7.4.6 | | 406 | Not Acceptable | Section 4.6.6 |
| 408 | Request Timeout | Section 7.4.7 | | 408 | Request Timeout | Section 4.6.7 |
| 409 | Conflict | Section 7.4.8 | | 409 | Conflict | Section 4.6.8 |
| 410 | Gone | Section 7.4.9 | | 410 | Gone | Section 4.6.9 |
| 411 | Length Required | Section 7.4.10 | | 411 | Length Required | Section 4.6.10 |
| 413 | Request Representation Too Large | Section 7.4.11 | | 413 | Request Representation Too Large | Section 4.6.11 |
| 414 | URI Too Long | Section 7.4.12 | | 414 | URI Too Long | Section 4.6.12 |
| 415 | Unsupported Media Type | Section 7.4.13 | | 415 | Unsupported Media Type | Section 4.6.13 |
| 417 | Expectation Failed | Section 7.4.14 | | 417 | Expectation Failed | Section 4.6.14 |
| 426 | Upgrade Required | Section 7.4.15 | | 426 | Upgrade Required | Section 4.6.15 |
| 500 | Internal Server Error | Section 7.5.1 | | 500 | Internal Server Error | Section 4.7.1 |
| 501 | Not Implemented | Section 7.5.2 | | 501 | Not Implemented | Section 4.7.2 |
| 502 | Bad Gateway | Section 7.5.3 | | 502 | Bad Gateway | Section 4.7.3 |
| 503 | Service Unavailable | Section 7.5.4 | | 503 | Service Unavailable | Section 4.7.4 |
| 504 | Gateway Timeout | Section 7.5.5 | | 504 | Gateway Timeout | Section 4.7.5 |
| 505 | HTTP Version Not Supported | Section 7.5.6 | | 505 | HTTP Version Not Supported | Section 4.7.6 |
+-------+----------------------------------+----------------+ +-------+----------------------------------+----------------+
11.3. 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 10.1 | | Accept | http | standard | Section 9.1 |
| Date | http | standard | Section 10.2 | | Accept-Charset | http | standard | Section 9.2 |
| Expect | http | standard | Section 10.3 | | Accept-Encoding | http | standard | Section 9.3 |
| From | http | standard | Section 10.4 | | Accept-Language | http | standard | Section 9.4 |
| Location | http | standard | Section 10.5 | | Allow | http | standard | Section 9.5 |
| Max-Forwards | http | standard | Section 10.6 | | Content-Encoding | http | standard | Section 9.6 |
| Referer | http | standard | Section 10.7 | | Content-Language | http | standard | Section 9.7 |
| Retry-After | http | standard | Section 10.8 | | Content-Location | http | standard | Section 9.8 |
| Server | http | standard | Section 10.9 | | Content-Type | http | standard | Section 9.9 |
| User-Agent | http | standard | Section 10.10 | | Date | http | standard | Section 9.10 |
+-------------------+----------+----------+---------------+ | Expect | http | standard | Section 9.11 |
| From | http | standard | Section 9.12 |
| Location | http | standard | Section 9.13 |
| MIME-Version | http | standard | Appendix A.1 |
| Max-Forwards | http | standard | Section 9.14 |
| Referer | http | standard | Section 9.15 |
| Retry-After | http | standard | Section 9.16 |
| Server | http | standard | Section 9.17 |
| User-Agent | http | standard | Section 9.18 |
+-------------------+----------+----------+--------------+
The change controller is: "IETF (iesg@ietf.org) - Internet The change controller is: "IETF (iesg@ietf.org) - Internet
Engineering Task Force". Engineering Task Force".
12. Security Considerations 10.4. Content Coding Registry
The registration procedure for HTTP Content Codings is now defined by
Section 5.4.1 of this document.
The HTTP Content Codings Registry located at
<http://www.iana.org/assignments/http-parameters> shall be updated
with the registration below:
+----------+------------------------------------------+-------------+
| Name | Description | Reference |
+----------+------------------------------------------+-------------+
| compress | UNIX "compress" program method | Section |
| | | 4.2.1 of |
| | | [Part1] |
| deflate | "deflate" compression mechanism | Section |
| | ([RFC1951]) used inside the "zlib" data | 4.2.2 of |
| | format ([RFC1950]) | [Part1] |
| gzip | Same as GNU zip [RFC1952] | Section |
| | | 4.2.3 of |
| | | [Part1] |
| identity | reserved (synonym for "no encoding" in | Section 9.3 |
| | Accept-Encoding header field) | |
+----------+------------------------------------------+-------------+
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
some suggestions for reducing security risks. some suggestions for reducing security risks.
12.1. Transfer of Sensitive Information 11.1. Transfer of Sensitive Information
Like any generic data transfer protocol, HTTP cannot regulate the Like any generic data transfer protocol, HTTP cannot regulate the
content of the data that is transferred, nor is there any a priori content of the data that is transferred, nor is there any a priori
method of determining the sensitivity of any particular piece of method of determining the sensitivity of any particular piece of
information within the context of any given request. Therefore, information within the context of any given request. Therefore,
applications SHOULD supply as much control over this information as applications SHOULD supply as much control over this information as
possible to the provider of that information. Four header fields are possible to the provider of that information. Four header fields are
worth special mention in this context: Server, Via, Referer and From. worth special mention in this context: Server, Via, Referer and From.
Revealing the specific software version of the server might allow the Revealing the specific software version of the server might allow the
server machine to become more vulnerable to attacks against software server machine to become more vulnerable to attacks against software
that is known to contain security holes. Implementors SHOULD make that is known to contain security holes. Implementers SHOULD make
the Server header field a configurable option. the Server header field a configurable option.
Proxies which serve as a portal through a network firewall SHOULD Proxies which serve as a portal through a network firewall SHOULD
take special precautions regarding the transfer of header information take special precautions regarding the transfer of header information
that identifies the hosts behind the firewall. In particular, they that identifies the hosts behind the firewall. In particular, they
SHOULD remove, or replace with sanitized versions, any Via fields SHOULD remove, or replace with sanitized versions, any Via fields
generated behind the firewall. generated behind the firewall.
The Referer header field allows reading patterns to be studied and The Referer header field allows reading patterns to be studied and
reverse links drawn. Although it can be very useful, its power can reverse links drawn. Although it can be very useful, its power can
skipping to change at page 52, line 21 skipping to change at page 72, line 7
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 10.10) or Server (Section 10.9) header fields The User-Agent (Section 9.18) or Server (Section 9.17) 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
has a particular security hole which might be exploited. has 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 might 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 6.8), expose information Some request methods, like TRACE (Section 2.3.7), 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.
12.2. 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
Referer field is sent. For example, a browser client could have a Referer field is sent. For example, a browser client could have a
toggle switch for browsing openly/anonymously, which would toggle switch for browsing openly/anonymously, which would
respectively enable/disable the sending of Referer and From respectively enable/disable the sending of Referer and From
information. information.
Clients SHOULD NOT include a Referer header field in a (non-secure) Clients SHOULD NOT include a Referer header field in a (non-secure)
HTTP request if the referring page was transferred with a secure HTTP request if the referring page was transferred with a secure
protocol. protocol.
Authors of services SHOULD NOT use GET-based forms for the submission Authors of services SHOULD NOT use GET-based forms for the submission
of sensitive data because that data will be placed in the request- of sensitive data because that data will be placed in the request-
target. Many existing servers, proxies, and user agents log or target. Many existing servers, proxies, and user agents log or
display the request-target in places where it might be visible to display the request-target in places where it might be visible to
third parties. Such services can use POST-based form submission third parties. Such services can use POST-based form submission
instead. instead.
12.3. Location Header Fields: Spoofing and Information Leakage 11.3. Location Header Fields: Spoofing and Information Leakage
If a single server supports multiple organizations that do not trust If a single server supports multiple organizations that do not trust
one another, then it MUST check the values of Location and Content- one another, then it MUST check the values of Location and Content-
Location header fields in responses that are generated under control Location header fields in responses that are generated under control
of said organizations to make sure that they do not attempt to of said organizations to make sure that they do not attempt to
invalidate resources over which they have no authority. invalidate resources over which they have no authority.
Furthermore, appending the fragment identifier from one URI to Furthermore, appending the fragment identifier from one URI to
another one obtained from a Location header field might leak another one obtained from a Location header field might leak
confidential information to the target server -- although the confidential information to the target server -- although the
fragment identifier is not transmitted in the final request, it might fragment identifier is not transmitted in the final request, it might
be visible to the user agent through other means, such as scripting. be visible to the user agent through other means, such as scripting.
12.4. 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.
13. Acknowledgments 11.5. Privacy Issues Connected to Accept Header Fields
Accept header fields can reveal information about the user to all
servers which are accessed. The Accept-Language header field in
particular can reveal information the user would consider to be of a
private nature, because the understanding of particular languages is
often strongly correlated to the membership of a particular ethnic
group. User agents which offer the option to configure the contents
of an Accept-Language header field to be sent in every request are
strongly encouraged to let the configuration process include a
message which makes the user aware of the loss of privacy involved.
An approach that limits the loss of privacy would be for a user agent
to omit the sending of Accept-Language header fields by default, and
to ask the user whether or not to start sending Accept-Language
header fields to a server if it detects, by looking for any Vary
header fields generated by the server, that such sending could
improve the quality of service.
Elaborate user-customized accept header fields sent in every request,
in particular if these include quality values, can be used by servers
as relatively reliable and long-lived user identifiers. Such user
identifiers would allow content providers to do click-trail tracking,
and would allow collaborating content providers to match cross-server
click-trails or form submissions of individual users. Note that for
many users not behind a proxy, the network address of the host
running the user agent will also serve as a long-lived user
identifier. In environments where proxies are used to enhance
privacy, user agents ought to be conservative in offering accept
header field configuration options to end users. As an extreme
privacy measure, proxies could filter the accept header fields in
relayed requests. General purpose user agents which provide a high
degree of header field configurability SHOULD warn users about the
loss of privacy which can be involved.
12. Acknowledgments
See Section 9 of [Part1]. See Section 9 of [Part1].
14. References 13. References
14.1. Normative References 13.1. Normative References
[Part1] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed., [Part1] Fielding, R., Ed., Lafon, Y., Ed.,
"HTTP/1.1, part 1: URIs, Connections, and Message and J. Reschke, Ed., "HTTP/1.1, part
Parsing", draft-ietf-httpbis-p1-messaging-19 (work in 1: Message Routing and Syntax"",
progress), March 2012. draft-ietf-httpbis-p1-messaging-20
(work in progress), July 2012.
[Part3] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed., [Part4] Fielding, R., Ed., Lafon, Y., Ed.,
"HTTP/1.1, part 3: Message Payload and Content and J. Reschke, Ed., "HTTP/1.1, part
Negotiation", draft-ietf-httpbis-p3-payload-19 (work in 4: Conditional Requests",
progress), March 2012. draft-ietf-httpbis-p4-conditional-20
(work in progress), July 2012.
[Part4] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed., [Part5] Fielding, R., Ed., Lafon, Y., Ed.,
"HTTP/1.1, part 4: Conditional Requests", and J. Reschke, Ed., "HTTP/1.1, part
draft-ietf-httpbis-p4-conditional-19 (work in progress), 5: Range Requests",
March 2012. draft-ietf-httpbis-p5-range-20 (work
in progress), July 2012.
[Part5] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed., [Part6] Fielding, R., Ed., Lafon, Y., Ed.,
"HTTP/1.1, part 5: Range Requests and Partial Responses", Nottingham, M., Ed., and J. Reschke,
draft-ietf-httpbis-p5-range-19 (work in progress), Ed., "HTTP/1.1, part 6: Caching",
March 2012. draft-ietf-httpbis-p6-cache-20 (work
in progress), July 2012.
[Part6] Fielding, R., Ed., Lafon, Y., Ed., Nottingham, M., Ed., [Part7] Fielding, R., Ed., Lafon, Y., Ed.,
and J. Reschke, Ed., "HTTP/1.1, part 6: Caching", and J. Reschke, Ed., "HTTP/1.1, part
draft-ietf-httpbis-p6-cache-19 (work in progress), 7: Authentication",
March 2012. draft-ietf-httpbis-p7-auth-20 (work
in progress), July 2012.
[Part7] Fielding, R., Ed., Lafon, Y., Ed., and J. Reschke, Ed., [RFC1950] Deutsch, L. and J-L. Gailly, "ZLIB
"HTTP/1.1, part 7: Authentication", Compressed Data Format Specification
draft-ietf-httpbis-p7-auth-19 (work in progress), version 3.3", RFC 1950, May 1996.
March 2012.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC1951] Deutsch, P., "DEFLATE Compressed
Requirement Levels", BCP 14, RFC 2119, March 1997. Data Format Specification version
1.3", RFC 1951, May 1996.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC1952] Deutsch, P., Gailly, J-L., Adler,
Resource Identifier (URI): Generic Syntax", STD 66, M., Deutsch, L., and G. Randers-
RFC 3986, January 2005. Pehrson, "GZIP file format
specification version 4.3",
RFC 1952, May 1996.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax [RFC2045] Freed, N. and N. Borenstein,
Specifications: ABNF", STD 68, RFC 5234, January 2008. "Multipurpose Internet Mail
Extensions (MIME) Part One: Format
of Internet Message Bodies",
RFC 2045, November 1996.
14.2. Informative References [RFC2046] Freed, N. and N. Borenstein,
"Multipurpose Internet Mail
Extensions (MIME) Part Two: Media
Types", RFC 2046, November 1996.
[RFC1123] Braden, R., "Requirements for Internet Hosts - Application [RFC2119] Bradner, S., "Key words for use in
and Support", STD 3, RFC 1123, October 1989. RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119,
March 1997.
[RFC1945] Berners-Lee, T., Fielding, R., and H. Nielsen, "Hypertext [RFC3986] Berners-Lee, T., Fielding, R., and
Transfer Protocol -- HTTP/1.0", RFC 1945, May 1996. L. Masinter, "Uniform Resource
Identifier (URI): Generic Syntax",
STD 66, RFC 3986, January 2005.
[RFC2068] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., and T. [RFC4647] Phillips, A., Ed. and M. Davis, Ed.,
Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", "Matching of Language Tags", BCP 47,
RFC 2068, January 1997. RFC 4647, September 2006.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., [RFC5234] Crocker, D., Ed. and P. Overell,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext "Augmented BNF for Syntax
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. Specifications: ABNF", STD 68,
RFC 5234, January 2008.
[RFC2817] Khare, R. and S. Lawrence, "Upgrading to TLS Within [RFC5646] Phillips, A., Ed. and M. Davis, Ed.,
HTTP/1.1", RFC 2817, May 2000. "Tags for Identifying Languages",
BCP 47, RFC 5646, September 2009.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration 13.2. Informative References
Procedures for Message Header Fields", BCP 90, RFC 3864,
September 2004.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an [RFC1123] Braden, R., "Requirements for
IANA Considerations Section in RFCs", BCP 26, RFC 5226, Internet Hosts - Application and
May 2008. Support", STD 3, RFC 1123,
October 1989.
[RFC5322] Resnick, P., "Internet Message Format", RFC 5322, [RFC1945] Berners-Lee, T., Fielding, R., and
October 2008. H. Nielsen, "Hypertext Transfer
Protocol -- HTTP/1.0", RFC 1945,
May 1996.
[RFC5789] Dusseault, L. and J. Snell, "PATCH Method for HTTP", [RFC2049] Freed, N. and N. Borenstein,
RFC 5789, March 2010. "Multipurpose Internet Mail
Extensions (MIME) Part Five:
Conformance Criteria and Examples",
RFC 2049, November 1996.
[RFC5987] Reschke, J., "Character Set and Language Encoding for [RFC2068] Fielding, R., Gettys, J., Mogul, J.,
Hypertext Transfer Protocol (HTTP) Header Field Nielsen, H., and T. Berners-Lee,
Parameters", RFC 5987, August 2010. "Hypertext Transfer Protocol --
HTTP/1.1", RFC 2068, January 1997.
Appendix A. Changes from RFC 2616 [RFC2076] Palme, J., "Common Internet Message
Headers", RFC 2076, February 1997.
This document takes over the Status Code Registry, previously defined [RFC2277] Alvestrand, H., "IETF Policy on
in Section 7.1 of [RFC2817]. (Section 4.2) Character Sets and Languages",
BCP 18, RFC 2277, January 1998.
Clarify definition of POST. (Section 6.5) [RFC2295] Holtman, K. and A. Mutz,
"Transparent Content Negotiation in
HTTP", RFC 2295, March 1998.
[RFC2388] Masinter, L., "Returning Values from
Forms: multipart/form-data",
RFC 2388, August 1998.
[RFC2557] Palme, F., Hopmann, A., Shelness,
N., and E. Stefferud, "MIME
Encapsulation of Aggregate
Documents, such as HTML (MHTML)",
RFC 2557, March 1999.
[RFC2616] Fielding, R., Gettys, J., Mogul, J.,
Frystyk, H., Masinter, L., Leach,
P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1",
RFC 2616, June 1999.
[RFC2817] Khare, R. and S. Lawrence,
"Upgrading to TLS Within HTTP/1.1",
RFC 2817, May 2000.
[RFC3629] Yergeau, F., "UTF-8, a
transformation format of ISO 10646",
STD 63, RFC 3629, November 2003.
[RFC3864] Klyne, G., Nottingham, M., and J.
Mogul, "Registration Procedures for
Message Header Fields", BCP 90,
RFC 3864, September 2004.
[RFC4288] Freed, N. and J. Klensin, "Media
Type Specifications and Registration
Procedures", BCP 13, RFC 4288,
December 2005.
[RFC5226] Narten, T. and H. Alvestrand,
"Guidelines for Writing an IANA
Considerations Section in RFCs",
BCP 26, RFC 5226, May 2008.
[RFC5322] Resnick, P., "Internet Message
Format", RFC 5322, October 2008.
[RFC5789] Dusseault, L. and J. Snell, "PATCH
Method for HTTP", RFC 5789,
March 2010.
[RFC5987] Reschke, J., "Character Set and
Language Encoding for Hypertext
Transfer Protocol (HTTP) Header
Field Parameters", RFC 5987,
August 2010.
[RFC6151] Turner, S. and L. Chen, "Updated
Security Considerations for the MD5
Message-Digest and the HMAC-MD5
Algorithms", RFC 6151, March 2011.
[RFC6266] Reschke, J., "Use of the Content-
Disposition Header Field in the
Hypertext Transfer Protocol (HTTP)",
RFC 6266, June 2011.
[draft-reschke-http-status-308] Reschke, J., "The Hypertext Transfer
Protocol (HTTP) Status Code 308
(Permanent Redirect)",
draft-reschke-http-status-308-07
(work in progress), March 2012.
Appendix A. Differences between HTTP and MIME
HTTP/1.1 uses many of the constructs defined for Internet Mail
([RFC5322]) and the Multipurpose Internet Mail Extensions (MIME
[RFC2045]) to allow a message body to be transmitted in an open
variety of representations and with extensible mechanisms. However,
RFC 2045 discusses mail, and HTTP has a few features that are
different from those described in MIME. These differences were
carefully chosen to optimize performance over binary connections, to
allow greater freedom in the use of new media types, to make date
comparisons easier, and to acknowledge the practice of some early
HTTP servers and clients.
This appendix describes specific areas where HTTP differs from MIME.
Proxies and gateways to strict MIME environments SHOULD be aware of
these differences and provide the appropriate conversions where
necessary. Proxies and gateways from MIME environments to HTTP also
need to be aware of the differences because some conversions might be
required.
A.1. MIME-Version
HTTP is not a MIME-compliant protocol. However, HTTP/1.1 messages
MAY include a single MIME-Version header field to indicate what
version of the MIME protocol was used to construct the message. Use
of the MIME-Version header field indicates that the message is in
full conformance with the MIME protocol (as defined in [RFC2045]).
Proxies/gateways are responsible for ensuring full conformance (where
possible) when exporting HTTP messages to strict MIME environments.
MIME-Version = 1*DIGIT "." 1*DIGIT
MIME version "1.0" is the default for use in HTTP/1.1. However,
HTTP/1.1 message parsing and semantics are defined by this document
and not the MIME specification.
A.2. Conversion to Canonical Form
MIME requires that an Internet mail body-part be converted to
canonical form prior to being transferred, as described in Section 4
of [RFC2049]. Section 5.5.1 of this document describes the forms
allowed for subtypes of the "text" media type when transmitted over
HTTP. [RFC2046] requires that content with a type of "text"
represent line breaks as CRLF and forbids the use of CR or LF outside
of line break sequences. HTTP allows CRLF, bare CR, and bare LF to
indicate a line break within text content when a message is
transmitted over HTTP.
Where it is possible, a proxy or gateway from HTTP to a strict MIME
environment SHOULD translate all line breaks within the text media
types described in Section 5.5.1 of this document to the RFC 2049
canonical form of CRLF. Note, however, that this might be
complicated by the presence of a Content-Encoding and by the fact
that HTTP allows the use of some character encodings which do not use
octets 13 and 10 to represent CR and LF, respectively, as is the case
for some multi-byte character encodings.
Conversion will break any cryptographic checksums applied to the
original content unless the original content is already in canonical
form. Therefore, the canonical form is recommended for any content
that uses such checksums in HTTP.
A.3. Conversion of Date Formats
HTTP/1.1 uses a restricted set of date formats (Section 5.1) to
simplify the process of date comparison. Proxies and gateways from
other protocols SHOULD ensure that any Date header field present in a
message conforms to one of the HTTP/1.1 formats and rewrite the date
if necessary.
A.4. Introduction of Content-Encoding
MIME does not include any concept equivalent to HTTP/1.1's Content-
Encoding header field. Since this acts as a modifier on the media
type, proxies and gateways from HTTP to MIME-compliant protocols MUST
either change the value of the Content-Type header field or decode
the representation before forwarding the message. (Some experimental
applications of Content-Type for Internet mail have used a media-type
parameter of ";conversions=<content-coding>" to perform a function
equivalent to Content-Encoding. However, this parameter is not part
of the MIME standards).
A.5. No Content-Transfer-Encoding
HTTP does not use the Content-Transfer-Encoding field of MIME.
Proxies and gateways from MIME-compliant protocols to HTTP MUST
remove any Content-Transfer-Encoding prior to delivering the response
message to an HTTP client.
Proxies and gateways from HTTP to MIME-compliant protocols are
responsible for ensuring that the message is in the correct format
and encoding for safe transport on that protocol, where "safe
transport" is defined by the limitations of the protocol being used.
Such a proxy or gateway SHOULD label the data with an appropriate
Content-Transfer-Encoding if doing so will improve the likelihood of
safe transport over the destination protocol.
A.6. MHTML and Line Length Limitations
HTTP implementations which share code with MHTML [RFC2557]
implementations need to be aware of MIME line length limitations.
Since HTTP does not have this limitation, HTTP does not fold long
lines. MHTML messages being transported by HTTP follow all
conventions of MHTML, including line length limitations and folding,
canonicalization, etc., since HTTP transports all message-bodies as
payload (see Section 5.5.2) and does not interpret the content or any
MIME header lines that might be contained therein.
Appendix B. Additional Features
[RFC1945] and [RFC2068] document protocol elements used by some
existing HTTP implementations, but not consistently and correctly
across most HTTP/1.1 applications. Implementers are advised to be
aware of these features, but cannot rely upon their presence in, or
interoperability with, other HTTP/1.1 applications. Some of these
describe proposed experimental features, and some describe features
that experimental deployment found lacking that are now addressed in
the base HTTP/1.1 specification.
A number of other header fields, such as Content-Disposition and
Title, from SMTP and MIME are also often implemented (see [RFC6266]
and [RFC2076]).
Appendix C. Changes from RFC 2616
Introduce Method Registry. (Section 2.2)
Clarify definition of POST. (Section 2.3.4)
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 6.6) Content-Range with PUT. (Section 2.3.5)
Take over definition of CONNECT method from [RFC2817]. (Section 6.9) Take over definition of CONNECT method from [RFC2817].
(Section 2.3.8)
Take over the Status Code Registry, previously defined in Section 7.1
of [RFC2817]. (Section 4.2)
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 7.2.4) include cases of payload transformations as well. (Section 4.4.4)
Status codes 301, 302, and 307: removed the normative requirements on Status codes 301, 302, and 307: removed the normative requirements on
both response payloads and user interaction. (Section 7.3) both response payloads and user interaction. (Section 4.5)
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. Furthermore, allow user agents to rewrite the method from 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 POST to GET for status codes 301 and 302. (Sections 4.5.2, 4.5.3 and
7.3.7) 4.5.7)
Deprecate 305 (Use Proxy) status code, because user agents did not
implement it. It used to indicate that the target resource needs to
be accessed through the proxy given by the Location field. The
Location field gave the URI of the proxy. The recipient was expected
to repeat this single request via the proxy. (Section 4.5.5)
Deprecate 305 Use Proxy status code, because user agents did not
implement it. It used to indicate that the target resource must be
accessed through the proxy given by the Location field. The Location
field gave the URI of the proxy. The recipient was expected to
repeat this single request via the proxy. (Section 7.3.5)
Define status 426 (Upgrade Required) (this was incorporated from Define status 426 (Upgrade Required) (this was incorporated from
[RFC2817]). (Section 7.4.15) [RFC2817]). (Section 4.6.15)
Change ABNF productions for header fields to only define the field Change ABNF productions for header fields to only define the field
value. (Section 10) 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 10.1) to always trust the header field value. (Section 9.5)
The ABNF for the Expect header field has been both fixed (allowing The ABNF for the Expect header field has been both fixed (allowing
parameters for value-less expectations as well) and simplified parameters for value-less expectations as well) and simplified
(allowing trailing semicolons after "100-continue" when they were (allowing trailing semicolons after "100-continue" when they were
invalid before). (Section 10.3) invalid before). (Section 9.11)
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 10.5) as to when use of fragments would not be appropriate. (Section 9.13)
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 10.6) extension methods could have used it as well). (Section 9.14)
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 10.7) specifying it. (Section 9.15)
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 6.2 of [Part1]. in the description of the Via header field in Section 6.2 of [Part1].
(Section 10.9) (Section 9.17)
Appendix B. Collected ABNF Clarify contexts that charset is used in. (Section 5.3)
Registration of Content Codings now requires IETF Review
(Section 5.4.1)
Remove the default character encoding of "ISO-8859-1" for text media
types; the default now is whatever the media type definition says.
(Section 5.5.1)
Change ABNF productions for header fields to only define the field
value. (Section 9)
Remove definition of Content-MD5 header field because it was
inconsistently implemented with respect to partial responses, and
also because of known deficiencies in the hash algorithm itself (see
[RFC6151] for details). (Section 9)
Remove ISO-8859-1 special-casing in Accept-Charset. (Section 9.2)
Remove base URI setting semantics for Content-Location due to poor
implementation support, which was caused by too many broken servers
emitting bogus Content-Location header fields, and also the
potentially undesirable effect of potentially breaking relative links
in content-negotiated resources. (Section 9.8)
Remove reference to non-existant identity transfer-coding value
tokens. (Appendix A.5)
Remove discussion of Content-Disposition header field, it is now
defined by [RFC6266]. (Appendix B)
Appendix D. Imported ABNF
The following core rules are included by reference, as defined in
Appendix B.1 of [RFC5234]: ALPHA (letters), CR (carriage return),
CRLF (CR LF), CTL (controls), DIGIT (decimal 0-9), DQUOTE (double
quote), HEXDIG (hexadecimal 0-9/A-F/a-f), HTAB (horizontal tab), LF
(line feed), OCTET (any 8-bit sequence of data), SP (space), and
VCHAR (any visible US-ASCII character).
The rules below are defined in [Part1]:
BWS = <BWS, defined in [Part1], Section 3.2.1>
OWS = <OWS, defined in [Part1], Section 3.2.1>
RWS = <RWS, defined in [Part1], Section 3.2.1>
quoted-string = <quoted-string, defined in [Part1], Section 3.2.4>
token = <token, defined in [Part1], Section 3.2.4>
word = <word, defined in [Part1], Section 3.2.4>
absolute-URI = <absolute-URI, defined in [Part1], Section 2.8>
comment = <comment, defined in [Part1], Section 3.2.4>
partial-URI = <partial-URI, defined in [Part1], Section 2.8>
qvalue = <qvalue, defined in [Part1], Section 4.3.1>
URI-reference = <URI-reference, defined in [Part1], Section 2.8>
Appendix E. Collected ABNF
Accept = [ ( "," / ( media-range [ accept-params ] ) ) *( OWS "," [
OWS ( media-range [ accept-params ] ) ] ) ]
Accept-Charset = *( "," OWS ) ( ( charset / "*" ) [ OWS ";" OWS "q="
qvalue ] ) *( OWS "," [ OWS ( ( charset / "*" ) [ OWS ";" OWS "q="
qvalue ] ) ] )
Accept-Encoding = [ ( "," / ( codings [ OWS ";" OWS "q=" qvalue ] ) )
*( OWS "," [ OWS ( codings [ OWS ";" OWS "q=" qvalue ] ) ] ) ]
Accept-Language = *( "," OWS ) ( language-range [ OWS ";" OWS "q="
qvalue ] ) *( OWS "," [ OWS ( language-range [ OWS ";" OWS "q="
qvalue ] ) ] )
Allow = [ ( "," / method ) *( OWS "," [ OWS method ] ) ] Allow = [ ( "," / method ) *( OWS "," [ OWS method ] ) ]
BWS = <BWS, defined in [Part1], Section 3.2.1> BWS = <BWS, defined in [Part1], Section 3.2.1>
Content-Encoding = *( "," OWS ) content-coding *( OWS "," [ OWS
content-coding ] )
Content-Language = *( "," OWS ) language-tag *( OWS "," [ OWS
language-tag ] )
Content-Location = absolute-URI / partial-URI
Content-Type = media-type
Date = HTTP-date Date = HTTP-date
Expect = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] ) Expect = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )
From = mailbox From = mailbox
GMT = %x47.4D.54 ; GMT GMT = %x47.4D.54 ; GMT
HTTP-date = rfc1123-date / obs-date HTTP-date = rfc1123-date / obs-date
Location = URI-reference Location = URI-reference
MIME-Version = 1*DIGIT "." 1*DIGIT
Max-Forwards = 1*DIGIT Max-Forwards = 1*DIGIT
OWS = <OWS, defined in [Part1], Section 3.2.1> OWS = <OWS, defined in [Part1], Section 3.2.1>
RWS = <RWS, defined in [Part1], Section 3.2.1> RWS = <RWS, defined in [Part1], Section 3.2.1>
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 ) )
URI-reference = <URI-reference, defined in [Part1], Section 2.8>
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 2.8>
accept-ext = OWS ";" OWS token [ "=" word ]
accept-params = OWS ";" OWS "q=" qvalue *accept-ext
asctime-date = day-name SP date3 SP time-of-day SP year asctime-date = day-name SP date3 SP time-of-day SP year
attribute = token
charset = token
codings = content-coding / "identity" / "*"
comment = <comment, defined in [Part1], Section 3.2.4> comment = <comment, defined in [Part1], Section 3.2.4>
content-coding = token
date1 = day SP month SP year date1 = day SP month SP year
date2 = day "-" month "-" 2DIGIT date2 = day "-" month "-" 2DIGIT
date3 = month SP ( 2DIGIT / ( SP DIGIT ) ) date3 = month SP ( 2DIGIT / ( SP DIGIT ) )
day = 2DIGIT day = 2DIGIT
day-name = %x4D.6F.6E ; Mon day-name = %x4D.6F.6E ; Mon
/ %x54.75.65 ; Tue / %x54.75.65 ; Tue
/ %x57.65.64 ; Wed / %x57.65.64 ; Wed
/ %x54.68.75 ; Thu / %x54.68.75 ; Thu
/ %x46.72.69 ; Fri / %x46.72.69 ; Fri
skipping to change at page 58, line 4 skipping to change at page 84, line 45
/ %x53.75.6E.64.61.79 ; Sunday / %x53.75.6E.64.61.79 ; Sunday
delta-seconds = 1*DIGIT delta-seconds = 1*DIGIT
expect-name = token expect-name = token
expect-param = expect-name [ BWS "=" BWS expect-value ] expect-param = expect-name [ BWS "=" BWS expect-value ]
expect-value = token / quoted-string expect-value = token / quoted-string
expectation = expect-name [ BWS "=" BWS expect-value ] *( OWS ";" [ expectation = expect-name [ BWS "=" BWS expect-value ] *( OWS ";" [
OWS expect-param ] ) OWS expect-param ] )
hour = 2DIGIT hour = 2DIGIT
language-range = <language-range, defined in [RFC4647], Section 2.1>
language-tag = <Language-Tag, defined in [RFC5646], Section 2.1>
mailbox = <mailbox, defined in [RFC5322], Section 3.4> mailbox = <mailbox, defined in [RFC5322], Section 3.4>
media-range = ( "*/*" / ( type "/*" ) / ( type "/" subtype ) ) *( OWS
";" OWS parameter )
media-type = type "/" subtype *( OWS ";" OWS parameter )
method = token method = token
minute = 2DIGIT minute = 2DIGIT
month = %x4A.61.6E ; Jan month = %x4A.61.6E ; Jan
/ %x46.65.62 ; Feb / %x46.65.62 ; Feb
/ %x4D.61.72 ; Mar / %x4D.61.72 ; Mar
/ %x41.70.72 ; Apr / %x41.70.72 ; Apr
/ %x4D.61.79 ; May / %x4D.61.79 ; May
/ %x4A.75.6E ; Jun / %x4A.75.6E ; Jun
/ %x4A.75.6C ; Jul / %x4A.75.6C ; Jul
/ %x41.75.67 ; Aug / %x41.75.67 ; Aug
/ %x53.65.70 ; Sep / %x53.65.70 ; Sep
/ %x4F.63.74 ; Oct / %x4F.63.74 ; Oct
/ %x4E.6F.76 ; Nov / %x4E.6F.76 ; Nov
/ %x44.65.63 ; Dec / %x44.65.63 ; Dec
obs-date = rfc850-date / asctime-date obs-date = rfc850-date / asctime-date
obs-text = <obs-text, defined in [Part1], Section 3.2.4>
partial-URI = <partial-URI, defined in [Part1], Section 2.7> parameter = attribute "=" value
partial-URI = <partial-URI, defined in [Part1], Section 2.8>
product = token [ "/" product-version ] product = token [ "/" product-version ]
product-version = token product-version = token
quoted-string = <quoted-string, defined in [Part1], Section 3.2.4> quoted-string = <quoted-string, defined in [Part1], Section 3.2.4>
qvalue = <qvalue, defined in [Part1], Section 4.3.1>
reason-phrase = *( HTAB / SP / VCHAR / obs-text )
rfc1123-date = day-name "," SP date1 SP time-of-day SP GMT 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 rfc850-date = day-name-l "," SP date2 SP time-of-day SP GMT
second = 2DIGIT second = 2DIGIT
status-code = 3DIGIT subtype = token
time-of-day = hour ":" minute ":" second time-of-day = hour ":" minute ":" second
token = <token, defined in [Part1], Section 3.2.4> token = <token, defined in [Part1], Section 3.2.4>
type = token
year = 4DIGIT value = word
ABNF diagnostics:
; Allow defined but not used word = <word, defined in [Part1], Section 3.2.4>
; Date defined but not used
; Expect defined but not used
; From defined but not used
; Location defined but not used
; Max-Forwards defined but not used
; Referer defined but not used
; Retry-After defined but not used
; Server defined but not used
; User-Agent defined but not used
; reason-phrase defined but not used
; status-code defined but not used
Appendix C. Change Log (to be removed by RFC Editor before publication) year = 4DIGIT
C.1. Since RFC 2616 Appendix F. Change Log (to be removed by RFC Editor before publication)
F.1. Since RFC 2616
Extracted relevant partitions from [RFC2616]. Extracted relevant partitions from [RFC2616].
C.2. Since draft-ietf-httpbis-p2-semantics-00 F.2. Since draft-ietf-httpbis-p2-semantics-00
Closed issues: Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/5>: "Via is a MUST" o <http://tools.ietf.org/wg/httpbis/trac/ticket/5>: "Via is a MUST"
(<http://purl.org/NET/http-errata#via-must>) (<http://purl.org/NET/http-errata#via-must>)
o <http://tools.ietf.org/wg/httpbis/trac/ticket/6>: "Fragments o <http://tools.ietf.org/wg/httpbis/trac/ticket/6>: "Fragments
allowed in Location" allowed in Location"
(<http://purl.org/NET/http-errata#location-fragments>) (<http://purl.org/NET/http-errata#location-fragments>)
skipping to change at page 60, line 12 skipping to change at page 86, line 39
o <http://tools.ietf.org/wg/httpbis/trac/ticket/65>: "Informative o <http://tools.ietf.org/wg/httpbis/trac/ticket/65>: "Informative
references" references"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/84>: "Redundant o <http://tools.ietf.org/wg/httpbis/trac/ticket/84>: "Redundant
cross-references" cross-references"
Other changes: Other changes:
o Move definitions of 304 and 412 condition codes to [Part4] o Move definitions of 304 and 412 condition codes to [Part4]
C.3. Since draft-ietf-httpbis-p2-semantics-01 F.3. Since draft-ietf-httpbis-p3-payload-00
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/8>: "Media Type
Registrations" (<http://purl.org/NET/http-errata#media-reg>)
o <http://tools.ietf.org/wg/httpbis/trac/ticket/14>: "Clarification
regarding quoting of charset values"
(<http://purl.org/NET/http-errata#charactersets>)
o <http://tools.ietf.org/wg/httpbis/trac/ticket/16>: "Remove
'identity' token references"
(<http://purl.org/NET/http-errata#identity>)
o <http://tools.ietf.org/wg/httpbis/trac/ticket/25>: "Accept-
Encoding BNF"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/35>: "Normative and
Informative references"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/46>: "RFC1700
references"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/55>: "Updating to
RFC4288"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/65>: "Informative
references"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/66>: "ISO-8859-1
Reference"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/68>: "Encoding
References Normative"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/86>: "Normative up-
to-date references"
F.4. Since draft-ietf-httpbis-p2-semantics-01
Closed issues: Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/21>: "PUT side o <http://tools.ietf.org/wg/httpbis/trac/ticket/21>: "PUT side
effects" effects"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/91>: "Duplicate Host o <http://tools.ietf.org/wg/httpbis/trac/ticket/91>: "Duplicate Host
header requirements" header requirements"
Ongoing work on ABNF conversion Ongoing work on ABNF conversion
skipping to change at page 60, line 34 skipping to change at page 88, line 5
o Move "Product Tokens" section (back) into Part 1, as "token" is o Move "Product Tokens" section (back) into Part 1, as "token" is
used in the definition of the Upgrade header field. used in the definition of the Upgrade header field.
o Add explicit references to BNF syntax and rules imported from o Add explicit references to BNF syntax and rules imported from
other parts of the specification. other parts of the specification.
o Copy definition of delta-seconds from Part6 instead of referencing o Copy definition of delta-seconds from Part6 instead of referencing
it. it.
C.4. Since draft-ietf-httpbis-p2-semantics-02 F.5. Since draft-ietf-httpbis-p3-payload-01
Ongoing work on ABNF conversion
(<http://tools.ietf.org/wg/httpbis/trac/ticket/36>):
o Add explicit references to BNF syntax and rules imported from
other parts of the specification.
F.6. Since draft-ietf-httpbis-p2-semantics-02
Closed issues: Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/24>: "Requiring o <http://tools.ietf.org/wg/httpbis/trac/ticket/24>: "Requiring
Allow in 405 responses" Allow in 405 responses"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/59>: "Status Code o <http://tools.ietf.org/wg/httpbis/trac/ticket/59>: "Status Code
Registry" Registry"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/61>: "Redirection o <http://tools.ietf.org/wg/httpbis/trac/ticket/61>: "Redirection
skipping to change at page 61, line 4 skipping to change at page 88, line 30
o <http://tools.ietf.org/wg/httpbis/trac/ticket/59>: "Status Code o <http://tools.ietf.org/wg/httpbis/trac/ticket/59>: "Status Code
Registry" Registry"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/61>: "Redirection o <http://tools.ietf.org/wg/httpbis/trac/ticket/61>: "Redirection
vs. Location" vs. Location"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/70>: "Cacheability o <http://tools.ietf.org/wg/httpbis/trac/ticket/70>: "Cacheability
of 303 response" of 303 response"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/76>: "305 Use Proxy" o <http://tools.ietf.org/wg/httpbis/trac/ticket/76>: "305 Use Proxy"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/105>: o <http://tools.ietf.org/wg/httpbis/trac/ticket/105>:
"Classification for Allow header" "Classification for Allow header field"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/112>: "PUT - 'store o <http://tools.ietf.org/wg/httpbis/trac/ticket/112>: "PUT - 'store
under' vs 'store at'" under' vs 'store at'"
Ongoing work on IANA Message Header Field Registration Ongoing work on IANA Message Header Field Registration
(<http://tools.ietf.org/wg/httpbis/trac/ticket/40>): (<http://tools.ietf.org/wg/httpbis/trac/ticket/40>):
o Reference RFC 3984, and update header field registrations for o Reference RFC 3984, and update header field registrations for
headers defined in this document. header fields defined in this document.
Ongoing work on ABNF conversion Ongoing work on ABNF conversion
(<http://tools.ietf.org/wg/httpbis/trac/ticket/36>): (<http://tools.ietf.org/wg/httpbis/trac/ticket/36>):
o Replace string literals when the string really is case-sensitive o Replace string literals when the string really is case-sensitive
(method). (method).
C.5. Since draft-ietf-httpbis-p2-semantics-03 F.7. Since draft-ietf-httpbis-p3-payload-02
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/67>: "Quoting
Charsets"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/105>:
"Classification for Allow header field"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/115>: "missing
default for qvalue in description of Accept-Encoding"
Ongoing work on IANA Message Header Field Registration
(<http://tools.ietf.org/wg/httpbis/trac/ticket/40>):
o Reference RFC 3984, and update header field registrations for
header fields defined in this document.
F.8. Since draft-ietf-httpbis-p2-semantics-03
Closed issues: Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/98>: "OPTIONS o <http://tools.ietf.org/wg/httpbis/trac/ticket/98>: "OPTIONS
request bodies" request bodies"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/119>: "Description o <http://tools.ietf.org/wg/httpbis/trac/ticket/119>: "Description
of CONNECT should refer to RFC2817" of CONNECT should refer to RFC2817"
o <http://tools.ietf.org/wg/httpbis/trac/ticket/125>: "Location o <http://tools.ietf.org/wg/httpbis/trac/ticket/125>: "Location
Content-Location reference request/response mixup" Content-Location reference request/response mixup"
Ongoing work on Method Registry Ongoing work on Method Registry
(<http://tools.ietf.org/wg/httpbis/trac/ticket/72>): (<http://tools.ietf.org/wg/httpbis/trac/ticket/72>):
o Added initial proposal for registration process, plus initial o Added initial proposal for registration process, plus initial
content (non-HTTP/1.1 methods to be added by a separate content (non-HTTP/1.1 methods to be added by a separate
specification). specification).
C.6. Since draft-ietf-httpbis-p2-semantics-04 F.9. Since draft-ietf-httpbis-p3-payload-03
Closed issues:
o <http://tools.ietf.org/wg/httpbis/trac/ticket/67>: "Quoting
Charsets"