source: draft-ietf-httpbis/05/p2-semantics.xml @ 1500

Last change on this file since 1500 was 1500, checked in by julian.reschke@…, 11 years ago

fix mime types

  • Property svn:eol-style set to native
  • Property svn:mime-type set to text/xml
File size: 143.8 KB
1<?xml version="1.0" encoding="utf-8"?>
2<?xml-stylesheet type='text/xsl' href='../myxml2rfc.xslt'?>
3<!DOCTYPE rfc [
4  <!ENTITY MAY "<bcp14 xmlns=''>MAY</bcp14>">
5  <!ENTITY MUST "<bcp14 xmlns=''>MUST</bcp14>">
6  <!ENTITY MUST-NOT "<bcp14 xmlns=''>MUST NOT</bcp14>">
7  <!ENTITY OPTIONAL "<bcp14 xmlns=''>OPTIONAL</bcp14>">
8  <!ENTITY RECOMMENDED "<bcp14 xmlns=''>RECOMMENDED</bcp14>">
9  <!ENTITY REQUIRED "<bcp14 xmlns=''>REQUIRED</bcp14>">
10  <!ENTITY SHALL "<bcp14 xmlns=''>SHALL</bcp14>">
11  <!ENTITY SHALL-NOT "<bcp14 xmlns=''>SHALL NOT</bcp14>">
12  <!ENTITY SHOULD "<bcp14 xmlns=''>SHOULD</bcp14>">
13  <!ENTITY SHOULD-NOT "<bcp14 xmlns=''>SHOULD NOT</bcp14>">
15  <!ENTITY ID-MONTH "November">
16  <!ENTITY ID-YEAR "2008">
17  <!ENTITY messaging                  "<xref target='Part1' xmlns:x=''/>">
18  <!ENTITY payload                    "<xref target='Part3' xmlns:x=''/>">
19  <!ENTITY conditional                "<xref target='Part4' xmlns:x=''/>">
20  <!ENTITY range                      "<xref target='Part5' xmlns:x=''/>">
21  <!ENTITY caching                    "<xref target='Part6' xmlns:x=''/>">
22  <!ENTITY auth                       "<xref target='Part7' xmlns:x=''/>">
23  <!ENTITY content-negotiation        "<xref target='Part3' x:rel='#content.negotiation' xmlns:x=''/>">
24  <!ENTITY notation-abnf              "<xref target='Part1' x:rel='#notation.abnf' xmlns:x=''/>">
25  <!ENTITY basic-rules                "<xref target='Part1' x:rel='#basic.rules' xmlns:x=''/>">
26  <!ENTITY uri                        "<xref target='Part1' x:rel='#uri' xmlns:x=''/>">
27  <!ENTITY full-date                  "<xref target='Part1' x:rel='' xmlns:x=''/>">
28  <!ENTITY http-url                   "<xref target='Part1' x:rel='#http-url' xmlns:x=''/>">
29  <!ENTITY http-version               "<xref target='Part1' x:rel='#http.version' xmlns:x=''/>">
30  <!ENTITY use100                     "<xref target='Part1' x:rel='#use.of.the.100.status' xmlns:x=''/>">
31  <!ENTITY qvalue                     "<xref target='Part3' x:rel='#quality.values' xmlns:x=''/>">
32  <!ENTITY header-accept              "<xref target='Part3' x:rel='#header.accept' xmlns:x=''/>">
33  <!ENTITY header-accept-charset      "<xref target='Part3' x:rel='#header.accept-charset' xmlns:x=''/>">
34  <!ENTITY header-accept-encoding     "<xref target='Part3' x:rel='#header.accept-encoding' xmlns:x=''/>">
35  <!ENTITY header-accept-language     "<xref target='Part3' x:rel='#header.accept-language' xmlns:x=''/>">
36  <!ENTITY header-accept-ranges       "<xref target='Part5' x:rel='#header.accept-ranges' xmlns:x=''/>">
37  <!ENTITY header-age                 "<xref target='Part6' x:rel='#header.age' xmlns:x=''/>">
38  <!ENTITY header-authorization       "<xref target='Part7' x:rel='#header.authorization' xmlns:x=''/>">
39  <!ENTITY header-cache-control       "<xref target='Part6' x:rel='#header.cache-control' xmlns:x=''/>">
40  <!ENTITY header-content-location    "<xref target='Part3' x:rel='#header.content-location' xmlns:x=''/>">
41  <!ENTITY header-content-range       "<xref target='Part5' x:rel='#header.content-range' xmlns:x=''/>">
42  <!ENTITY header-etag                "<xref target='Part4' x:rel='#header.etag' xmlns:x=''/>">
43  <!ENTITY header-expires             "<xref target='Part6' x:rel='#header.expires' xmlns:x=''/>">
44  <!ENTITY header-host                "<xref target='Part1' x:rel='' xmlns:x=''/>">
45  <!ENTITY header-if-match            "<xref target='Part4' x:rel='#header.if-match' xmlns:x=''/>">
46  <!ENTITY header-if-modified-since   "<xref target='Part4' x:rel='#header.if-modified-since' xmlns:x=''/>">
47  <!ENTITY header-if-none-match       "<xref target='Part4' x:rel='#header.if-none-match' xmlns:x=''/>">
48  <!ENTITY header-if-range            "<xref target='Part5' x:rel='#header.if-range' xmlns:x=''/>">
49  <!ENTITY header-if-unmodified-since "<xref target='Part4' x:rel='#header.if-unmodified-since' xmlns:x=''/>">
50  <!ENTITY header-pragma              "<xref target='Part6' x:rel='#header.pragma' xmlns:x=''/>">
51  <!ENTITY header-proxy-authenticate  "<xref target='Part7' x:rel='#header.proxy-authenticate' xmlns:x=''/>">
52  <!ENTITY header-proxy-authorization "<xref target='Part7' x:rel='#header.proxy-authorization' xmlns:x=''/>">
53  <!ENTITY header-range               "<xref target='Part5' x:rel='#header.range' xmlns:x=''/>">
54  <!ENTITY header-upgrade             "<xref target='Part5' x:rel='#header.range' xmlns:x=''/>">
55  <!ENTITY header-te                  "<xref target='Part1' x:rel='#header.upgrade' xmlns:x=''/>">
56  <!ENTITY header-vary                "<xref target='Part6' x:rel='#header.vary' xmlns:x=''/>">
57  <!ENTITY header-via                 "<xref target='Part1' x:rel='#header.via' xmlns:x=''/>">
58  <!ENTITY header-warning             "<xref target='Part6' x:rel='#header.warning' xmlns:x=''/>">
59  <!ENTITY header-www-authenticate    "<xref target='Part7' x:rel='#header.www-authenticate' xmlns:x=''/>">
60  <!ENTITY message-body               "<xref target='Part1' x:rel='#message.body' xmlns:x=''/>">
61  <!ENTITY product-tokens             "<xref target='Part1' x:rel='#product.tokens' xmlns:x=''/>">
62  <!ENTITY media-type-message-http    "<xref target='Part1' x:rel='' xmlns:x=''/>">
64<?rfc toc="yes" ?>
65<?rfc symrefs="yes" ?>
66<?rfc sortrefs="yes" ?>
67<?rfc compact="yes"?>
68<?rfc subcompact="no" ?>
69<?rfc linkmailto="no" ?>
70<?rfc editing="no" ?>
71<?rfc comments="yes"?>
72<?rfc inline="yes"?>
73<?rfc-ext allow-markup-in-artwork="yes" ?>
74<?rfc-ext include-references-in-index="yes" ?>
75<rfc obsoletes="2616" updates="2817" category="std" x:maturity-level="draft"
76     ipr="full3978" docName="draft-ietf-httpbis-p2-semantics-&ID-VERSION;"
77     xmlns:x=''
78     xmlns:rdf=''>
81  <title abbrev="HTTP/1.1, Part 2">HTTP/1.1, part 2: Message Semantics</title>
83  <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
84    <organization abbrev="Day Software">Day Software</organization>
85    <address>
86      <postal>
87        <street>23 Corporate Plaza DR, Suite 280</street>
88        <city>Newport Beach</city>
89        <region>CA</region>
90        <code>92660</code>
91        <country>USA</country>
92      </postal>
93      <phone>+1-949-706-5300</phone>
94      <facsimile>+1-949-706-5305</facsimile>
95      <email></email>
96      <uri></uri>
97    </address>
98  </author>
100  <author initials="J." surname="Gettys" fullname="Jim Gettys">
101    <organization>One Laptop per Child</organization>
102    <address>
103      <postal>
104        <street>21 Oak Knoll Road</street>
105        <city>Carlisle</city>
106        <region>MA</region>
107        <code>01741</code>
108        <country>USA</country>
109      </postal>
110      <email></email>
111      <uri></uri>
112    </address>
113  </author>
115  <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
116    <organization abbrev="HP">Hewlett-Packard Company</organization>
117    <address>
118      <postal>
119        <street>HP Labs, Large Scale Systems Group</street>
120        <street>1501 Page Mill Road, MS 1177</street>
121        <city>Palo Alto</city>
122        <region>CA</region>
123        <code>94304</code>
124        <country>USA</country>
125      </postal>
126      <email></email>
127    </address>
128  </author>
130  <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
131    <organization abbrev="Microsoft">Microsoft Corporation</organization>
132    <address>
133      <postal>
134        <street>1 Microsoft Way</street>
135        <city>Redmond</city>
136        <region>WA</region>
137        <code>98052</code>
138        <country>USA</country>
139      </postal>
140      <email></email>
141    </address>
142  </author>
144  <author initials="L." surname="Masinter" fullname="Larry Masinter">
145    <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
146    <address>
147      <postal>
148        <street>345 Park Ave</street>
149        <city>San Jose</city>
150        <region>CA</region>
151        <code>95110</code>
152        <country>USA</country>
153      </postal>
154      <email></email>
155      <uri></uri>
156    </address>
157  </author>
159  <author initials="P." surname="Leach" fullname="Paul J. Leach">
160    <organization abbrev="Microsoft">Microsoft Corporation</organization>
161    <address>
162      <postal>
163        <street>1 Microsoft Way</street>
164        <city>Redmond</city>
165        <region>WA</region>
166        <code>98052</code>
167      </postal>
168      <email></email>
169    </address>
170  </author>
172  <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
173    <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
174    <address>
175      <postal>
176        <street>MIT Computer Science and Artificial Intelligence Laboratory</street>
177        <street>The Stata Center, Building 32</street>
178        <street>32 Vassar Street</street>
179        <city>Cambridge</city>
180        <region>MA</region>
181        <code>02139</code>
182        <country>USA</country>
183      </postal>
184      <email></email>
185      <uri></uri>
186    </address>
187  </author>
189  <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
190    <organization abbrev="W3C">World Wide Web Consortium</organization>
191    <address>
192      <postal>
193        <street>W3C / ERCIM</street>
194        <street>2004, rte des Lucioles</street>
195        <city>Sophia-Antipolis</city>
196        <region>AM</region>
197        <code>06902</code>
198        <country>France</country>
199      </postal>
200      <email></email>
201      <uri></uri>
202    </address>
203  </author>
205  <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
206    <organization abbrev="greenbytes">greenbytes GmbH</organization>
207    <address>
208      <postal>
209        <street>Hafenweg 16</street>
210        <city>Muenster</city><region>NW</region><code>48155</code>
211        <country>Germany</country>
212      </postal>
213      <phone>+49 251 2807760</phone>   
214      <facsimile>+49 251 2807761</facsimile>   
215      <email></email>       
216      <uri></uri>     
217    </address>
218  </author>
220  <date month="&ID-MONTH;" year="&ID-YEAR;" day="16"/>
224   The Hypertext Transfer Protocol (HTTP) is an application-level
225   protocol for distributed, collaborative, hypermedia information
226   systems. HTTP has been in use by the World Wide Web global information
227   initiative since 1990. This document is Part 2 of the seven-part specification
228   that defines the protocol referred to as "HTTP/1.1" and, taken together,
229   obsoletes RFC 2616.  Part 2 defines the semantics of HTTP messages
230   as expressed by request methods, request-header fields, response status codes,
231   and response-header fields.
235<note title="Editorial Note (To be removed by RFC Editor)">
236  <t>
237    Discussion of this draft should take place on the HTTPBIS working group
238    mailing list ( The current issues list is
239    at <eref target=""/>
240    and related documents (including fancy diffs) can be found at
241    <eref target=""/>.
242  </t>
243  <t>
244    The changes in this draft are summarized in <xref target="changes.since.04"/>.
245  </t>
249<section title="Introduction" anchor="introduction">
251   This document defines HTTP/1.1 request and response semantics.  Each HTTP
252   message, as defined in &messaging;, is in the form of either a request or
253   a response.  An HTTP server listens on a connection for HTTP requests and
254   responds to each request, in the order received on that connection, with
255   one or more HTTP response messages.  This document defines the commonly
256   agreed upon semantics of the HTTP uniform interface, the intentions defined
257   by each request method, and the various response messages that might be
258   expected as a result of applying that method for the requested resource.
261   This document is currently disorganized in order to minimize the changes
262   between drafts and enable reviewers to see the smaller errata changes.
263   The next draft will reorganize the sections to better reflect the content.
264   In particular, the sections will be ordered according to the typical
265   processing of an HTTP request message (after message parsing): resource
266   mapping, general header fields, methods, request modifiers, response
267   status, and resource metadata.  The current mess reflects how widely
268   dispersed these topics and associated requirements had become in
269   <xref target="RFC2616"/>.
272<section title="Requirements" anchor="intro.requirements">
274   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
275   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
276   document are to be interpreted as described in <xref target="RFC2119"/>.
279   An implementation is not compliant if it fails to satisfy one or more
280   of the &MUST; or &REQUIRED; level requirements for the protocols it
281   implements. An implementation that satisfies all the &MUST; or &REQUIRED;
282   level and all the &SHOULD; level requirements for its protocols is said
283   to be "unconditionally compliant"; one that satisfies all the &MUST;
284   level requirements but not all the &SHOULD; level requirements for its
285   protocols is said to be "conditionally compliant."
290<section title="Notational Conventions and Generic Grammar" anchor="notation">
291  <x:anchor-alias value="comment"/>
292  <x:anchor-alias value="DIGIT"/>
293  <x:anchor-alias value="quoted-string"/>
294  <x:anchor-alias value="token"/>
295  <x:anchor-alias value="OWS"/>
296  <x:anchor-alias value="RWS"/>
298  This specification uses the ABNF syntax defined in &notation-abnf; and
299  the core rules defined in &basic-rules;:
301<figure><artwork type="abnf2616">
302  <x:ref>DIGIT</x:ref>         = &lt;DIGIT, defined in &basic-rules;&gt;
304<figure><artwork type="abnf2616">
305  <x:ref>comment</x:ref>       = &lt;comment, defined in &basic-rules;&gt;
306  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
307  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
308  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
309  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
311<t anchor="abnf.dependencies">
312  <x:anchor-alias value="absolute-URI"/>
313  <x:anchor-alias value="Accept"/>
314  <x:anchor-alias value="Accept-Charset"/>
315  <x:anchor-alias value="Accept-Encoding"/>
316  <x:anchor-alias value="Accept-Language"/>
317  <x:anchor-alias value="Accept-Ranges"/>
318  <x:anchor-alias value="Age"/>
319  <x:anchor-alias value="Authorization"/>
320  <x:anchor-alias value="ETag"/>
321  <x:anchor-alias value="fragment"/>
322  <x:anchor-alias value="Host"/>
323  <x:anchor-alias value="HTTP-date"/>
324  <x:anchor-alias value="If-Match"/>
325  <x:anchor-alias value="If-Modified-Since"/>
326  <x:anchor-alias value="If-None-Match"/>
327  <x:anchor-alias value="If-Range"/>
328  <x:anchor-alias value="If-Unmodified-Since"/>
329  <x:anchor-alias value="product"/>
330  <x:anchor-alias value="Proxy-Authenticate"/>
331  <x:anchor-alias value="Proxy-Authorization"/>
332  <x:anchor-alias value="Range"/>
333  <x:anchor-alias value="relativeURI"/>
334  <x:anchor-alias value="TE"/>
335  <x:anchor-alias value="Vary"/>
336  <x:anchor-alias value="WWW-Authenticate"/>
337  The ABNF rules below are defined in other parts:
339<figure><!--Part1--><artwork type="abnf2616">
340  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
341  <x:ref>fragment</x:ref>      = &lt;fragment, defined in &uri;&gt;
342  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
343  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
344  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
345  <x:ref>relativeURI</x:ref>   = &lt;relativeURI, defined in &uri;&gt;
346  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
348<figure><!--Part3--><artwork type="abnf2616">
349  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
350  <x:ref>Accept-Charset</x:ref> =
351             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
352  <x:ref>Accept-Encoding</x:ref> =
353             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
354  <x:ref>Accept-Language</x:ref> =
355             &lt;Accept-Language, defined in &header-accept-language;&gt;
357<figure><!--Part4--><artwork type="abnf2616">
358  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
359  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
360  <x:ref>If-Modified-Since</x:ref> =
361             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
362  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
363  <x:ref>If-Unmodified-Since</x:ref> =
364             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
366<figure><!--Part5--><artwork type="abnf2616">
367  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
368  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
369  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
371<figure><!--Part6--><artwork type="abnf2616">
372  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
373  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
375<figure><artwork type="abnf2616">
376  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
377  <x:ref>Proxy-Authenticate</x:ref> =
378             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
379  <x:ref>Proxy-Authorization</x:ref> =
380             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
381  <x:ref>WWW-Authenticate</x:ref> =
382             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
386<section title="Method" anchor="method">
387  <x:anchor-alias value="Method"/>
388  <x:anchor-alias value="extension-method"/>
390   The Method  token indicates the method to be performed on the
391   resource identified by the Request-URI. The method is case-sensitive.
393<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
394  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
395                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
396                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
397                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
398                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
399                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
400                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
401                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
402                 / <x:ref>extension-method</x:ref>
403  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
406   The list of methods allowed by a resource can be specified in an
407   Allow header field (<xref target="header.allow"/>). The return code of the response
408   always notifies the client whether a method is currently allowed on a
409   resource, since the set of allowed methods can change dynamically. An
410   origin server &SHOULD; return the status code 405 (Method Not Allowed)
411   if the method is known by the origin server but not allowed for the
412   requested resource, and 501 (Not Implemented) if the method is
413   unrecognized or not implemented by the origin server. The methods GET
414   and HEAD &MUST; be supported by all general-purpose servers. All other
415   methods are &OPTIONAL;; however, if the above methods are implemented,
416   they &MUST; be implemented with the same semantics as those specified
417   in <xref target="method.definitions"/>.
420<section title="Method Registry" anchor="method.registry">
422  The HTTP Method Registry defines the name space for the Method token in the
423  Request line of an HTTP request.
426  Registrations &MUST; include the following fields:
427  <list style="symbols">
428    <t>Method Name (see <xref target="method"/>)</t>
429    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
430    <t>Pointer to specification text</t>
431  </list>
434  Values to be added to this name space are subject to IETF review
435  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
436  new method names should be traceable through statuses of either 'Obsoletes'
437  or 'Updates' to this document.
440  The registry itself is maintained at <eref target=""/>.
445<section title="Request Header Fields" anchor="request.header.fields">
446  <x:anchor-alias value="extension-code"/>
447  <x:anchor-alias value="request-header"/>
449   The request-header fields allow the client to pass additional
450   information about the request, and about the client itself, to the
451   server. These fields act as request modifiers, with semantics
452   equivalent to the parameters on a programming language method
453   invocation.
455<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
456  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
457                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
458                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
459                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
460                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
461                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
462                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
463                 / <x:ref>Host</x:ref>                     ; &header-host;
464                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
465                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
466                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
467                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
468                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
469                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
470                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
471                 / <x:ref>Range</x:ref>                    ; &header-range;
472                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
473                 / <x:ref>TE</x:ref>                       ; &header-te;
474                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
477   Request-header field names can be extended reliably only in
478   combination with a change in the protocol version. However, new or
479   experimental header fields &MAY; be given the semantics of request-header
480   fields if all parties in the communication recognize them to
481   be request-header fields. Unrecognized header fields are treated as
482   entity-header fields.
486<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
487  <x:anchor-alias value="Reason-Phrase"/>
488  <x:anchor-alias value="Status-Code"/>
490   The Status-Code element is a 3-digit integer result code of the
491   attempt to understand and satisfy the request. The status codes listed
492   below are defined in <xref target=""/>.
493   The Reason-Phrase is intended to give a short
494   textual description of the Status-Code. The Status-Code is intended
495   for use by automata and the Reason-Phrase is intended for the human
496   user. The client is not required to examine or display the Reason-Phrase.
499   The individual values of the numeric status codes defined for
500   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
501   presented below. The reason phrases listed here are only
502   recommendations -- they &MAY; be replaced by local equivalents without
503   affecting the protocol.
505<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Status-Code"/><iref primary="true" item="Grammar" subitem="extension-code"/><iref primary="true" item="Grammar" subitem="Reason-Phrase"/>
506  <x:ref>Status-Code</x:ref>    =
507         "100"  ; <xref target="status.100"/>: Continue
508       / "101"  ; <xref target="status.101"/>: Switching Protocols
509       / "200"  ; <xref target="status.200"/>: OK
510       / "201"  ; <xref target="status.201"/>: Created
511       / "202"  ; <xref target="status.202"/>: Accepted
512       / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
513       / "204"  ; <xref target="status.204"/>: No Content
514       / "205"  ; <xref target="status.205"/>: Reset Content
515       / "206"  ; <xref target="status.206"/>: Partial Content
516       / "300"  ; <xref target="status.300"/>: Multiple Choices
517       / "301"  ; <xref target="status.301"/>: Moved Permanently
518       / "302"  ; <xref target="status.302"/>: Found
519       / "303"  ; <xref target="status.303"/>: See Other
520       / "304"  ; <xref target="status.304"/>: Not Modified
521       / "305"  ; <xref target="status.305"/>: Use Proxy
522       / "307"  ; <xref target="status.307"/>: Temporary Redirect
523       / "400"  ; <xref target="status.400"/>: Bad Request
524       / "401"  ; <xref target="status.401"/>: Unauthorized
525       / "402"  ; <xref target="status.402"/>: Payment Required
526       / "403"  ; <xref target="status.403"/>: Forbidden
527       / "404"  ; <xref target="status.404"/>: Not Found
528       / "405"  ; <xref target="status.405"/>: Method Not Allowed
529       / "406"  ; <xref target="status.406"/>: Not Acceptable
530       / "407"  ; <xref target="status.407"/>: Proxy Authentication Required
531       / "408"  ; <xref target="status.408"/>: Request Time-out
532       / "409"  ; <xref target="status.409"/>: Conflict
533       / "410"  ; <xref target="status.410"/>: Gone
534       / "411"  ; <xref target="status.411"/>: Length Required
535       / "412"  ; <xref target="status.412"/>: Precondition Failed
536       / "413"  ; <xref target="status.413"/>: Request Entity Too Large
537       / "414"  ; <xref target="status.414"/>: Request-URI Too Large
538       / "415"  ; <xref target="status.415"/>: Unsupported Media Type
539       / "416"  ; <xref target="status.416"/>: Requested range not satisfiable
540       / "417"  ; <xref target="status.417"/>: Expectation Failed
541       / "500"  ; <xref target="status.500"/>: Internal Server Error
542       / "501"  ; <xref target="status.501"/>: Not Implemented
543       / "502"  ; <xref target="status.502"/>: Bad Gateway
544       / "503"  ; <xref target="status.503"/>: Service Unavailable
545       / "504"  ; <xref target="status.504"/>: Gateway Time-out
546       / "505"  ; <xref target="status.505"/>: HTTP Version not supported
547       / <x:ref>extension-code</x:ref>
549  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
550  <x:ref>Reason-Phrase</x:ref>  = *&lt;<x:ref>TEXT</x:ref>, excluding <x:ref>CR</x:ref>, <x:ref>LF</x:ref>&gt;
553   HTTP status codes are extensible. HTTP applications are not required
554   to understand the meaning of all registered status codes, though such
555   understanding is obviously desirable. However, applications &MUST;
556   understand the class of any status code, as indicated by the first
557   digit, and treat any unrecognized response as being equivalent to the
558   x00 status code of that class, with the exception that an
559   unrecognized response &MUST-NOT; be cached. For example, if an
560   unrecognized status code of 431 is received by the client, it can
561   safely assume that there was something wrong with its request and
562   treat the response as if it had received a 400 status code. In such
563   cases, user agents &SHOULD; present to the user the entity returned
564   with the response, since that entity is likely to include human-readable
565   information which will explain the unusual status.
568<section title="Status Code Registry" anchor="status.code.registry">
570  The HTTP Status Code Registry defines the name space for the Status-Code
571  token in the Status line of an HTTP response.
574  Values to be added to this name space are subject to IETF review
575  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
576  new status codes should be traceable through statuses of either 'Obsoletes'
577  or 'Updates' to this document.
580  The registry itself is maintained at <eref target=""/>.
586<section title="Response Header Fields" anchor="response.header.fields">
587  <x:anchor-alias value="response-header"/>
589   The response-header fields allow the server to pass additional
590   information about the response which cannot be placed in the Status-Line.
591   These header fields give information about the server and about
592   further access to the resource identified by the Request-URI.
594<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
595  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
596                  / <x:ref>Age</x:ref>                     ; &header-age;
597                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
598                  / <x:ref>ETag</x:ref>                    ; &header-etag;
599                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
600                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
601                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
602                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
603                  / <x:ref>Vary</x:ref>                    ; &header-vary;
604                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
607   Response-header field names can be extended reliably only in
608   combination with a change in the protocol version. However, new or
609   experimental header fields &MAY; be given the semantics of response-header
610   fields if all parties in the communication recognize them to
611   be response-header fields. Unrecognized header fields are treated as
612   entity-header fields.
616<section title="Entity" anchor="entity">
618   Request and Response messages &MAY; transfer an entity if not otherwise
619   restricted by the request method or response status code. An entity
620   consists of entity-header fields and an entity-body, although some
621   responses will only include the entity-headers. HTTP entity-body and
622   entity-header fields are defined in &payload;.
625   An entity-body is only present in a message when a message-body is
626   present, as described in &message-body;. The entity-body is obtained
627   from the message-body by decoding any Transfer-Encoding that might
628   have been applied to ensure safe and proper transfer of the message.
633<section title="Method Definitions" anchor="method.definitions">
635   The set of common methods for HTTP/1.1 is defined below. Although
636   this set can be expanded, additional methods cannot be assumed to
637   share the same semantics for separately extended clients and servers.
640<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
642<section title="Safe Methods" anchor="safe.methods">
643<iref item="Safe Methods" primary="true"/>
645   Implementors should be aware that the software represents the user in
646   their interactions over the Internet, and should be careful to allow
647   the user to be aware of any actions they might take which may have an
648   unexpected significance to themselves or others.
651   In particular, the convention has been established that the GET and
652   HEAD methods &SHOULD-NOT;  have the significance of taking an action
653   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
654   This allows user agents to represent other methods, such as POST, PUT
655   and DELETE, in a special way, so that the user is made aware of the
656   fact that a possibly unsafe action is being requested.
659   Naturally, it is not possible to ensure that the server does not
660   generate side-effects as a result of performing a GET request; in
661   fact, some dynamic resources consider that a feature. The important
662   distinction here is that the user did not request the side-effects,
663   so therefore cannot be held accountable for them.
667<section title="Idempotent Methods" anchor="idempotent.methods">
668<iref item="Idempotent Methods" primary="true"/>
670   Methods can also have the property of "idempotence" in that (aside
671   from error or expiration issues) the side-effects of N &gt; 0 identical
672   requests is the same as for a single request. The methods GET, HEAD,
673   PUT and DELETE share this property. Also, the methods OPTIONS and
674   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
677   However, it is possible that a sequence of several requests is non-idempotent,
678   even if all of the methods executed in that sequence are
679   idempotent. (A sequence is idempotent if a single execution of the
680   entire sequence always yields a result that is not changed by a
681   reexecution of all, or part, of that sequence.) For example, a
682   sequence is non-idempotent if its result depends on a value that is
683   later modified in the same sequence.
686   A sequence that never has side effects is idempotent, by definition
687   (provided that no concurrent operations are being executed on the
688   same set of resources).
693<section title="OPTIONS" anchor="OPTIONS">
694  <rdf:Description>
695    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
696  </rdf:Description>
697  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
698  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
700   The OPTIONS method represents a request for information about the
701   communication options available on the request/response chain
702   identified by the Request-URI. This method allows the client to
703   determine the options and/or requirements associated with a resource,
704   or the capabilities of a server, without implying a resource action
705   or initiating a resource retrieval.
708   Responses to this method are not cacheable.
711   If the OPTIONS request includes an entity-body (as indicated by the
712   presence of Content-Length or Transfer-Encoding), then the media type
713   &MUST; be indicated by a Content-Type field. Although this
714   specification does not define any use for such a body, future
715   extensions to HTTP might use the OPTIONS body to make more detailed
716   queries on the server.
719   If the Request-URI is an asterisk ("*"), the OPTIONS request is
720   intended to apply to the server in general rather than to a specific
721   resource. Since a server's communication options typically depend on
722   the resource, the "*" request is only useful as a "ping" or "no-op"
723   type of method; it does nothing beyond allowing the client to test
724   the capabilities of the server. For example, this can be used to test
725   a proxy for HTTP/1.1 compliance (or lack thereof).
728   If the Request-URI is not an asterisk, the OPTIONS request applies
729   only to the options that are available when communicating with that
730   resource.
733   A 200 response &SHOULD; include any header fields that indicate
734   optional features implemented by the server and applicable to that
735   resource (e.g., Allow), possibly including extensions not defined by
736   this specification. The response body, if any, &SHOULD; also include
737   information about the communication options. The format for such a
738   body is not defined by this specification, but might be defined by
739   future extensions to HTTP. Content negotiation &MAY; be used to select
740   the appropriate response format. If no response body is included, the
741   response &MUST; include a Content-Length field with a field-value of
742   "0".
745   The Max-Forwards request-header field &MAY; be used to target a
746   specific proxy in the request chain. When a proxy receives an OPTIONS
747   request on an absolute-URI for which request forwarding is permitted,
748   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
749   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
750   instead, the proxy &SHOULD; respond with its own communication options.
751   If the Max-Forwards field-value is an integer greater than zero, the
752   proxy &MUST; decrement the field-value when it forwards the request. If
753   no Max-Forwards field is present in the request, then the forwarded
754   request &MUST-NOT; include a Max-Forwards field.
758<section title="GET" anchor="GET">
759  <rdf:Description>
760    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
761  </rdf:Description>
762  <iref primary="true" item="GET method" x:for-anchor=""/>
763  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
765   The GET method means retrieve whatever information (in the form of an
766   entity) is identified by the Request-URI. If the Request-URI refers
767   to a data-producing process, it is the produced data which shall be
768   returned as the entity in the response and not the source text of the
769   process, unless that text happens to be the output of the process.
772   The semantics of the GET method change to a "conditional GET" if the
773   request message includes an If-Modified-Since, If-Unmodified-Since,
774   If-Match, If-None-Match, or If-Range header field. A conditional GET
775   method requests that the entity be transferred only under the
776   circumstances described by the conditional header field(s). The
777   conditional GET method is intended to reduce unnecessary network
778   usage by allowing cached entities to be refreshed without requiring
779   multiple requests or transferring data already held by the client.
782   The semantics of the GET method change to a "partial GET" if the
783   request message includes a Range header field. A partial GET requests
784   that only part of the entity be transferred, as described in &header-range;.
785   The partial GET method is intended to reduce unnecessary
786   network usage by allowing partially-retrieved entities to be
787   completed without transferring data already held by the client.
790   The response to a GET request is cacheable if and only if it meets
791   the requirements for HTTP caching described in &caching;.
794   See <xref target=""/> for security considerations when used for forms.
798<section title="HEAD" anchor="HEAD">
799  <rdf:Description>
800    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
801  </rdf:Description>
802  <iref primary="true" item="HEAD method" x:for-anchor=""/>
803  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
805   The HEAD method is identical to GET except that the server &MUST-NOT;
806   return a message-body in the response. The metainformation contained
807   in the HTTP headers in response to a HEAD request &SHOULD; be identical
808   to the information sent in response to a GET request. This method can
809   be used for obtaining metainformation about the entity implied by the
810   request without transferring the entity-body itself. This method is
811   often used for testing hypertext links for validity, accessibility,
812   and recent modification.
815   The response to a HEAD request &MAY; be cacheable in the sense that the
816   information contained in the response &MAY; be used to update a
817   previously cached entity from that resource. If the new field values
818   indicate that the cached entity differs from the current entity (as
819   would be indicated by a change in Content-Length, Content-MD5, ETag
820   or Last-Modified), then the cache &MUST; treat the cache entry as
821   stale.
825<section title="POST" anchor="POST">
826  <iref primary="true" item="POST method" x:for-anchor=""/>
827  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
829   The POST method is used to request that the origin server accept the
830   entity enclosed in the request as data to be processed by the resource
831   identified by the Request-URI in the Request-Line. POST is designed
832   to allow a uniform method to cover the following functions:
833  <list style="symbols">
834    <t>
835      Annotation of existing resources;
836    </t>
837    <t>
838        Posting a message to a bulletin board, newsgroup, mailing list,
839        or similar group of articles;
840    </t>
841    <t>
842        Providing a block of data, such as the result of submitting a
843        form, to a data-handling process;
844    </t>
845    <t>
846        Extending a database through an append operation.
847    </t>
848  </list>
851   The actual function performed by the POST method is determined by the
852   server and is usually dependent on the Request-URI.
855   The action performed by the POST method might not result in a
856   resource that can be identified by a URI. In this case, either 200
857   (OK) or 204 (No Content) is the appropriate response status,
858   depending on whether or not the response includes an entity that
859   describes the result.
862   If a resource has been created on the origin server, the response
863   &SHOULD; be 201 (Created) and contain an entity which describes the
864   status of the request and refers to the new resource, and a Location
865   header (see <xref target="header.location"/>).
868   Responses to this method are not cacheable, unless the response
869   includes appropriate Cache-Control or Expires header fields. However,
870   the 303 (See Other) response can be used to direct the user agent to
871   retrieve a cacheable resource.
875<section title="PUT" anchor="PUT">
876  <iref primary="true" item="PUT method" x:for-anchor=""/>
877  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
879   The PUT method requests that the enclosed entity be stored at the
880   supplied Request-URI. If the Request-URI refers to an already
881   existing resource, the enclosed entity &SHOULD; be considered as a
882   modified version of the one residing on the origin server. If the
883   Request-URI does not point to an existing resource, and that URI is
884   capable of being defined as a new resource by the requesting user
885   agent, the origin server can create the resource with that URI. If a
886   new resource is created at the Request-URI, the origin server &MUST;
887         inform the user agent
888   via the 201 (Created) response. If an existing resource is modified,
889   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
890   to indicate successful completion of the request. If the resource
891   could not be created or modified with the Request-URI, an appropriate
892   error response &SHOULD; be given that reflects the nature of the
893   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
894   headers (headers starting with the prefix 'Content-') that it does
895   not understand or implement
896   and &MUST; return a 501 (Not Implemented) response in such cases.
899   If the request passes through a cache and the Request-URI identifies
900   one or more currently cached entities, those entries &SHOULD; be
901   treated as stale. Responses to this method are not cacheable.
904   The fundamental difference between the POST and PUT requests is
905   reflected in the different meaning of the Request-URI. The URI in a
906   POST request identifies the resource that will handle the enclosed
907   entity. That resource might be a data-accepting process, a gateway to
908   some other protocol, or a separate entity that accepts annotations.
909   In contrast, the URI in a PUT request identifies the entity enclosed
910   with the request -- the user agent knows what URI is intended and the
911   server &MUST-NOT; attempt to apply the request to some other resource.
912   If the server desires that the request be applied to a different URI,
913   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
914   then make its own decision regarding whether or not to redirect the
915   request.
918   A single resource &MAY; be identified by many different URIs. For
919   example, an article might have a URI for identifying "the current
920   version" which is separate from the URI identifying each particular
921   version. In this case, a PUT request on a general URI might result in
922   several other URIs being defined by the origin server.
925   HTTP/1.1 does not define how a PUT method affects the state of an
926   origin server.
929   Unless otherwise specified for a particular entity-header, the
930   entity-headers in the PUT request &SHOULD; be applied to the resource
931   created or modified by the PUT.
935<section title="DELETE" anchor="DELETE">
936  <iref primary="true" item="DELETE method" x:for-anchor=""/>
937  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
939   The DELETE method requests that the origin server delete the resource
940   identified by the Request-URI. This method &MAY; be overridden by human
941   intervention (or other means) on the origin server. The client cannot
942   be guaranteed that the operation has been carried out, even if the
943   status code returned from the origin server indicates that the action
944   has been completed successfully. However, the server &SHOULD-NOT;
945   indicate success unless, at the time the response is given, it
946   intends to delete the resource or move it to an inaccessible
947   location.
950   A successful response &SHOULD; be 200 (OK) if the response includes an
951   entity describing the status, 202 (Accepted) if the action has not
952   yet been enacted, or 204 (No Content) if the action has been enacted
953   but the response does not include an entity.
956   If the request passes through a cache and the Request-URI identifies
957   one or more currently cached entities, those entries &SHOULD; be
958   treated as stale. Responses to this method are not cacheable.
962<section title="TRACE" anchor="TRACE">
963  <rdf:Description>
964    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
965  </rdf:Description>
966  <iref primary="true" item="TRACE method" x:for-anchor=""/>
967  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
969   The TRACE method is used to invoke a remote, application-layer loop-back
970   of the request message. The final recipient of the request
971   &SHOULD; reflect the message received back to the client as the
972   entity-body of a 200 (OK) response. The final recipient is either the
973   origin server or the first proxy or gateway to receive a Max-Forwards
974   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
975   &MUST-NOT; include an entity.
978   TRACE allows the client to see what is being received at the other
979   end of the request chain and use that data for testing or diagnostic
980   information. The value of the Via header field (&header-via;) is of
981   particular interest, since it acts as a trace of the request chain.
982   Use of the Max-Forwards header field allows the client to limit the
983   length of the request chain, which is useful for testing a chain of
984   proxies forwarding messages in an infinite loop.
987   If the request is valid, the response &SHOULD; contain the entire
988   request message in the entity-body, with a Content-Type of
989   "message/http" (see &media-type-message-http;). Responses to this method
990   &MUST-NOT; be cached.
994<section title="CONNECT" anchor="CONNECT">
995  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
996  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
998   This specification reserves the method name CONNECT for use with a
999   proxy that can dynamically switch to being a tunnel (e.g. SSL
1000   tunneling <xref target="RFC2817"/>).
1006<section title="Status Code Definitions" anchor="">
1008   Each Status-Code is described below, including a description of which
1009   method(s) it can follow and any metainformation required in the
1010   response.
1013<section title="Informational 1xx" anchor="status.1xx">
1015   This class of status code indicates a provisional response,
1016   consisting only of the Status-Line and optional headers, and is
1017   terminated by an empty line. There are no required headers for this
1018   class of status code. Since HTTP/1.0 did not define any 1xx status
1019   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1020   except under experimental conditions.
1023   A client &MUST; be prepared to accept one or more 1xx status responses
1024   prior to a regular response, even if the client does not expect a 100
1025   (Continue) status message. Unexpected 1xx status responses &MAY; be
1026   ignored by a user agent.
1029   Proxies &MUST; forward 1xx responses, unless the connection between the
1030   proxy and its client has been closed, or unless the proxy itself
1031   requested the generation of the 1xx response. (For example, if a
1032   proxy adds a "Expect: 100-continue" field when it forwards a request,
1033   then it need not forward the corresponding 100 (Continue)
1034   response(s).)
1037<section title="100 Continue" anchor="status.100">
1038  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1039  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1041   The client &SHOULD; continue with its request. This interim response is
1042   used to inform the client that the initial part of the request has
1043   been received and has not yet been rejected by the server. The client
1044   &SHOULD; continue by sending the remainder of the request or, if the
1045   request has already been completed, ignore this response. The server
1046   &MUST; send a final response after the request has been completed. See
1047   &use100; for detailed discussion of the use and handling of this
1048   status code.
1052<section title="101 Switching Protocols" anchor="status.101">
1053  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1054  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1056   The server understands and is willing to comply with the client's
1057   request, via the Upgrade message header field (&header-upgrade;), for a
1058   change in the application protocol being used on this connection. The
1059   server will switch protocols to those defined by the response's
1060   Upgrade header field immediately after the empty line which
1061   terminates the 101 response.
1064   The protocol &SHOULD; be switched only when it is advantageous to do
1065   so. For example, switching to a newer version of HTTP is advantageous
1066   over older versions, and switching to a real-time, synchronous
1067   protocol might be advantageous when delivering resources that use
1068   such features.
1073<section title="Successful 2xx" anchor="status.2xx">
1075   This class of status code indicates that the client's request was
1076   successfully received, understood, and accepted.
1079<section title="200 OK" anchor="status.200">
1080  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1081  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1083   The request has succeeded. The information returned with the response
1084   is dependent on the method used in the request, for example:
1085  <list style="hanging">
1086    <t hangText="GET">
1087          an entity corresponding to the requested resource is sent in
1088          the response;
1089    </t>
1090    <t hangText="HEAD">
1091          the entity-header fields corresponding to the requested
1092          resource are sent in the response without any message-body;
1093    </t>
1094    <t hangText="POST">
1095      an entity describing or containing the result of the action;
1096    </t>
1097    <t hangText="TRACE">
1098      an entity containing the request message as received by the
1099      end server.
1100    </t>
1101  </list>
1105<section title="201 Created" anchor="status.201">
1106  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1107  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1109   The request has been fulfilled and resulted in a new resource being
1110   created. The newly created resource can be referenced by the URI(s)
1111   returned in the entity of the response, with the most specific URI
1112   for the resource given by a Location header field. The response
1113   &SHOULD; include an entity containing a list of resource
1114   characteristics and location(s) from which the user or user agent can
1115   choose the one most appropriate. The entity format is specified by
1116   the media type given in the Content-Type header field. The origin
1117   server &MUST; create the resource before returning the 201 status code.
1118   If the action cannot be carried out immediately, the server &SHOULD;
1119   respond with 202 (Accepted) response instead.
1122   A 201 response &MAY; contain an ETag response header field indicating
1123   the current value of the entity tag for the requested variant just
1124   created, see &header-etag;.
1128<section title="202 Accepted" anchor="status.202">
1129  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1130  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1132   The request has been accepted for processing, but the processing has
1133   not been completed.  The request might or might not eventually be
1134   acted upon, as it might be disallowed when processing actually takes
1135   place. There is no facility for re-sending a status code from an
1136   asynchronous operation such as this.
1139   The 202 response is intentionally non-committal. Its purpose is to
1140   allow a server to accept a request for some other process (perhaps a
1141   batch-oriented process that is only run once per day) without
1142   requiring that the user agent's connection to the server persist
1143   until the process is completed. The entity returned with this
1144   response &SHOULD; include an indication of the request's current status
1145   and either a pointer to a status monitor or some estimate of when the
1146   user can expect the request to be fulfilled.
1150<section title="203 Non-Authoritative Information" anchor="status.203">
1151  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1152  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1154   The returned metainformation in the entity-header is not the
1155   definitive set as available from the origin server, but is gathered
1156   from a local or a third-party copy. The set presented &MAY; be a subset
1157   or superset of the original version. For example, including local
1158   annotation information about the resource might result in a superset
1159   of the metainformation known by the origin server. Use of this
1160   response code is not required and is only appropriate when the
1161   response would otherwise be 200 (OK).
1165<section title="204 No Content" anchor="status.204">
1166  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1167  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1169   The server has fulfilled the request but does not need to return an
1170   entity-body, and might want to return updated metainformation. The
1171   response &MAY; include new or updated metainformation in the form of
1172   entity-headers, which if present &SHOULD; be associated with the
1173   requested variant.
1176   If the client is a user agent, it &SHOULD-NOT;  change its document view
1177   from that which caused the request to be sent. This response is
1178   primarily intended to allow input for actions to take place without
1179   causing a change to the user agent's active document view, although
1180   any new or updated metainformation &SHOULD; be applied to the document
1181   currently in the user agent's active view.
1184   The 204 response &MUST-NOT; include a message-body, and thus is always
1185   terminated by the first empty line after the header fields.
1189<section title="205 Reset Content" anchor="status.205">
1190  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1191  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1193   The server has fulfilled the request and the user agent &SHOULD; reset
1194   the document view which caused the request to be sent. This response
1195   is primarily intended to allow input for actions to take place via
1196   user input, followed by a clearing of the form in which the input is
1197   given so that the user can easily initiate another input action. The
1198   response &MUST-NOT; include an entity.
1202<section title="206 Partial Content" anchor="status.206">
1203  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1204  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1206   The server has fulfilled the partial GET request for the resource
1207   and the enclosed entity is a partial representation as defined in &range;.
1212<section title="Redirection 3xx" anchor="status.3xx">
1214   This class of status code indicates that further action needs to be
1215   taken by the user agent in order to fulfill the request.  The action
1216   required &MAY; be carried out by the user agent without interaction
1217   with the user if and only if the method used in the second request is
1218   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1219   such loops generate network traffic for each redirection.
1220  <list><t>
1221      <x:h>Note:</x:h> previous versions of this specification recommended a
1222      maximum of five redirections. Content developers should be aware
1223      that there might be clients that implement such a fixed
1224      limitation.
1225  </t></list>
1228<section title="300 Multiple Choices" anchor="status.300">
1229  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1230  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1232   The requested resource corresponds to any one of a set of
1233   representations, each with its own specific location, and agent-driven
1234   negotiation information (&content-negotiation;) is being provided so that
1235   the user (or user agent) can select a preferred representation and
1236   redirect its request to that location.
1239   Unless it was a HEAD request, the response &SHOULD; include an entity
1240   containing a list of resource characteristics and location(s) from
1241   which the user or user agent can choose the one most appropriate. The
1242   entity format is specified by the media type given in the Content-Type
1243   header field. Depending upon the format and the capabilities of
1244   the user agent, selection of the most appropriate choice &MAY; be
1245   performed automatically. However, this specification does not define
1246   any standard for such automatic selection.
1249   If the server has a preferred choice of representation, it &SHOULD;
1250   include the specific URI for that representation in the Location
1251   field; user agents &MAY; use the Location field value for automatic
1252   redirection. This response is cacheable unless indicated otherwise.
1256<section title="301 Moved Permanently" anchor="status.301">
1257  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1258  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1260   The requested resource has been assigned a new permanent URI and any
1261   future references to this resource &SHOULD; use one of the returned
1262   URIs.  Clients with link editing capabilities ought to automatically
1263   re-link references to the Request-URI to one or more of the new
1264   references returned by the server, where possible. This response is
1265   cacheable unless indicated otherwise.
1268   The new permanent URI &SHOULD; be given by the Location field in the
1269   response. Unless the request method was HEAD, the entity of the
1270   response &SHOULD; contain a short hypertext note with a hyperlink to
1271   the new URI(s).
1274   If the 301 status code is received in response to a request method
1275   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1276   then the request &MAY; be automatically redirected by the user agent without
1277   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1278   request unless it can be confirmed by the user, since this might
1279   change the conditions under which the request was issued.
1280  <list><t>
1281      <x:h>Note:</x:h> When automatically redirecting a POST request after
1282      receiving a 301 status code, some existing HTTP/1.0 user agents
1283      will erroneously change it into a GET request.
1284  </t></list>
1288<section title="302 Found" anchor="status.302">
1289  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1290  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1292   The requested resource resides temporarily under a different URI.
1293   Since the redirection might be altered on occasion, the client &SHOULD;
1294   continue to use the Request-URI for future requests.  This response
1295   is only cacheable if indicated by a Cache-Control or Expires header
1296   field.
1299   The temporary URI &SHOULD; be given by the Location field in the
1300   response. Unless the request method was HEAD, the entity of the
1301   response &SHOULD; contain a short hypertext note with a hyperlink to
1302   the new URI(s).
1305   If the 302 status code is received in response to a request method
1306   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1307   then the request &MAY; be automatically redirected by the user agent without
1308   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1309   request unless it can be confirmed by the user, since this might
1310   change the conditions under which the request was issued.
1311  <list><t>
1312      <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1313      to change the method on the redirected request.  However, most
1314      existing user agent implementations treat 302 as if it were a 303
1315      response, performing a GET on the Location field-value regardless
1316      of the original request method. The status codes 303 and 307 have
1317      been added for servers that wish to make unambiguously clear which
1318      kind of reaction is expected of the client.
1319  </t></list>
1323<section title="303 See Other" anchor="status.303">
1324  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1325  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1327   The server directs the user agent to a different resource, indicated
1328   by a URI in the Location header field, that provides an indirect
1329   response to the original request.  The user agent &MAY; perform a GET
1330   request on the URI in the Location field in order to obtain a
1331   representation corresponding to the response, be redirected again,
1332   or end with an error status.  The Location URI is not a substitute
1333   reference for the originally requested resource.
1336   The 303 status is generally applicable to any HTTP method.  It is
1337   primarily used to allow the output of a POST action to redirect
1338   the user agent to a selected resource, since doing so provides the
1339   information corresponding to the POST response in a form that
1340   can be separately identified, bookmarked, and cached independent
1341   of the original request.
1344   A 303 response to a GET request indicates that the requested
1345   resource does not have a representation of its own that can be
1346   transferred by the server over HTTP.  The Location URI indicates a
1347   resource that is descriptive of the requested resource such that
1348   the follow-on representation may be useful without implying that
1349   it adequately represents the previously requested resource.
1350   Note that answers to the questions of what can be represented, what
1351   representations are adequate, and what might be a useful description
1352   are outside the scope of HTTP and thus entirely determined by the
1353   resource owner(s).
1356   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1357   cacheable by Cache-Control or Expires header fields.  Except for
1358   responses to a HEAD request, the entity of a 303 response &SHOULD;
1359   contain a short hypertext note with a hyperlink to the Location URI.
1363<section title="304 Not Modified" anchor="status.304">
1364  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1365  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1367   The response to the request has not been modified since the conditions
1368   indicated by the client's conditional GET request, as defined in &conditional;.
1372<section title="305 Use Proxy" anchor="status.305">
1373  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1374  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1376   The 305 status was defined in a previous version of this specification
1377   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1381<section title="306 (Unused)" anchor="status.306">
1382  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1383  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1385   The 306 status code was used in a previous version of the
1386   specification, is no longer used, and the code is reserved.
1390<section title="307 Temporary Redirect" anchor="status.307">
1391  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1392  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1394   The requested resource resides temporarily under a different URI.
1395   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1396   continue to use the Request-URI for future requests.  This response
1397   is only cacheable if indicated by a Cache-Control or Expires header
1398   field.
1401   The temporary URI &SHOULD; be given by the Location field in the
1402   response. Unless the request method was HEAD, the entity of the
1403   response &SHOULD; contain a short hypertext note with a hyperlink to
1404   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1405   understand the 307 status. Therefore, the note &SHOULD; contain the
1406   information necessary for a user to repeat the original request on
1407   the new URI.
1410   If the 307 status code is received in response to a request method
1411   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1412   then the request &MAY; be automatically redirected by the user agent without
1413   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1414   request unless it can be confirmed by the user, since this might
1415   change the conditions under which the request was issued.
1420<section title="Client Error 4xx" anchor="status.4xx">
1422   The 4xx class of status code is intended for cases in which the
1423   client seems to have erred. Except when responding to a HEAD request,
1424   the server &SHOULD; include an entity containing an explanation of the
1425   error situation, and whether it is a temporary or permanent
1426   condition. These status codes are applicable to any request method.
1427   User agents &SHOULD; display any included entity to the user.
1430   If the client is sending data, a server implementation using TCP
1431   &SHOULD; be careful to ensure that the client acknowledges receipt of
1432   the packet(s) containing the response, before the server closes the
1433   input connection. If the client continues sending data to the server
1434   after the close, the server's TCP stack will send a reset packet to
1435   the client, which may erase the client's unacknowledged input buffers
1436   before they can be read and interpreted by the HTTP application.
1439<section title="400 Bad Request" anchor="status.400">
1440  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1441  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1443   The request could not be understood by the server due to malformed
1444   syntax. The client &SHOULD-NOT;  repeat the request without
1445   modifications.
1449<section title="401 Unauthorized" anchor="status.401">
1450  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1451  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1453   The request requires user authentication (see &auth;).
1457<section title="402 Payment Required" anchor="status.402">
1458  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1459  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1461   This code is reserved for future use.
1465<section title="403 Forbidden" anchor="status.403">
1466  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1467  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1469   The server understood the request, but is refusing to fulfill it.
1470   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1471   If the request method was not HEAD and the server wishes to make
1472   public why the request has not been fulfilled, it &SHOULD; describe the
1473   reason for the refusal in the entity.  If the server does not wish to
1474   make this information available to the client, the status code 404
1475   (Not Found) can be used instead.
1479<section title="404 Not Found" anchor="status.404">
1480  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1481  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1483   The server has not found anything matching the Request-URI. No
1484   indication is given of whether the condition is temporary or
1485   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1486   knows, through some internally configurable mechanism, that an old
1487   resource is permanently unavailable and has no forwarding address.
1488   This status code is commonly used when the server does not wish to
1489   reveal exactly why the request has been refused, or when no other
1490   response is applicable.
1494<section title="405 Method Not Allowed" anchor="status.405">
1495  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1496  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1498   The method specified in the Request-Line is not allowed for the
1499   resource identified by the Request-URI. The response &MUST; include an
1500   Allow header containing a list of valid methods for the requested
1501   resource.
1505<section title="406 Not Acceptable" anchor="status.406">
1506  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1507  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1509   The resource identified by the request is only capable of generating
1510   response entities which have content characteristics not acceptable
1511   according to the accept headers sent in the request.
1514   Unless it was a HEAD request, the response &SHOULD; include an entity
1515   containing a list of available entity characteristics and location(s)
1516   from which the user or user agent can choose the one most
1517   appropriate. The entity format is specified by the media type given
1518   in the Content-Type header field. Depending upon the format and the
1519   capabilities of the user agent, selection of the most appropriate
1520   choice &MAY; be performed automatically. However, this specification
1521   does not define any standard for such automatic selection.
1522  <list><t>
1523      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1524      not acceptable according to the accept headers sent in the
1525      request. In some cases, this may even be preferable to sending a
1526      406 response. User agents are encouraged to inspect the headers of
1527      an incoming response to determine if it is acceptable.
1528  </t></list>
1531   If the response could be unacceptable, a user agent &SHOULD;
1532   temporarily stop receipt of more data and query the user for a
1533   decision on further actions.
1537<section title="407 Proxy Authentication Required" anchor="status.407">
1538  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1539  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1541   This code is similar to 401 (Unauthorized), but indicates that the
1542   client must first authenticate itself with the proxy (see &auth;).
1546<section title="408 Request Timeout" anchor="status.408">
1547  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1548  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1550   The client did not produce a request within the time that the server
1551   was prepared to wait. The client &MAY; repeat the request without
1552   modifications at any later time.
1556<section title="409 Conflict" anchor="status.409">
1557  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1558  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1560   The request could not be completed due to a conflict with the current
1561   state of the resource. This code is only allowed in situations where
1562   it is expected that the user might be able to resolve the conflict
1563   and resubmit the request. The response body &SHOULD; include enough
1564   information for the user to recognize the source of the conflict.
1565   Ideally, the response entity would include enough information for the
1566   user or user agent to fix the problem; however, that might not be
1567   possible and is not required.
1570   Conflicts are most likely to occur in response to a PUT request. For
1571   example, if versioning were being used and the entity being PUT
1572   included changes to a resource which conflict with those made by an
1573   earlier (third-party) request, the server might use the 409 response
1574   to indicate that it can't complete the request. In this case, the
1575   response entity would likely contain a list of the differences
1576   between the two versions in a format defined by the response
1577   Content-Type.
1581<section title="410 Gone" anchor="status.410">
1582  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1583  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1585   The requested resource is no longer available at the server and no
1586   forwarding address is known. This condition is expected to be
1587   considered permanent. Clients with link editing capabilities &SHOULD;
1588   delete references to the Request-URI after user approval. If the
1589   server does not know, or has no facility to determine, whether or not
1590   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1591   used instead. This response is cacheable unless indicated otherwise.
1594   The 410 response is primarily intended to assist the task of web
1595   maintenance by notifying the recipient that the resource is
1596   intentionally unavailable and that the server owners desire that
1597   remote links to that resource be removed. Such an event is common for
1598   limited-time, promotional services and for resources belonging to
1599   individuals no longer working at the server's site. It is not
1600   necessary to mark all permanently unavailable resources as "gone" or
1601   to keep the mark for any length of time -- that is left to the
1602   discretion of the server owner.
1606<section title="411 Length Required" anchor="status.411">
1607  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1608  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1610   The server refuses to accept the request without a defined Content-Length.
1611   The client &MAY; repeat the request if it adds a valid
1612   Content-Length header field containing the length of the message-body
1613   in the request message.
1617<section title="412 Precondition Failed" anchor="status.412">
1618  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1619  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1621   The precondition given in one or more of the request-header fields
1622   evaluated to false when it was tested on the server, as defined in
1623   &conditional;.
1627<section title="413 Request Entity Too Large" anchor="status.413">
1628  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1629  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1631   The server is refusing to process a request because the request
1632   entity is larger than the server is willing or able to process. The
1633   server &MAY; close the connection to prevent the client from continuing
1634   the request.
1637   If the condition is temporary, the server &SHOULD; include a Retry-After
1638   header field to indicate that it is temporary and after what
1639   time the client &MAY; try again.
1643<section title="414 Request-URI Too Long" anchor="status.414">
1644  <iref primary="true" item="414 Request-URI Too Long (status code)" x:for-anchor=""/>
1645  <iref primary="true" item="Status Codes" subitem="414 Request-URI Too Long" x:for-anchor=""/>
1647   The server is refusing to service the request because the Request-URI
1648   is longer than the server is willing to interpret. This rare
1649   condition is only likely to occur when a client has improperly
1650   converted a POST request to a GET request with long query
1651   information, when the client has descended into a URI "black hole" of
1652   redirection (e.g., a redirected URI prefix that points to a suffix of
1653   itself), or when the server is under attack by a client attempting to
1654   exploit security holes present in some servers using fixed-length
1655   buffers for reading or manipulating the Request-URI.
1659<section title="415 Unsupported Media Type" anchor="status.415">
1660  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1661  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1663   The server is refusing to service the request because the entity of
1664   the request is in a format not supported by the requested resource
1665   for the requested method.
1669<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1670  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1671  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1673   The request included a Range request-header field (&header-range;) and none of
1674   the range-specifier values in this field overlap the current extent
1675   of the selected resource.
1679<section title="417 Expectation Failed" anchor="status.417">
1680  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1681  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1683   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1684   could not be met by this server, or, if the server is a proxy,
1685   the server has unambiguous evidence that the request could not be met
1686   by the next-hop server.
1691<section title="Server Error 5xx" anchor="status.5xx">
1693   Response status codes beginning with the digit "5" indicate cases in
1694   which the server is aware that it has erred or is incapable of
1695   performing the request. Except when responding to a HEAD request, the
1696   server &SHOULD; include an entity containing an explanation of the
1697   error situation, and whether it is a temporary or permanent
1698   condition. User agents &SHOULD; display any included entity to the
1699   user. These response codes are applicable to any request method.
1702<section title="500 Internal Server Error" anchor="status.500">
1703  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1704  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1706   The server encountered an unexpected condition which prevented it
1707   from fulfilling the request.
1711<section title="501 Not Implemented" anchor="status.501">
1712  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1713  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1715   The server does not support the functionality required to fulfill the
1716   request. This is the appropriate response when the server does not
1717   recognize the request method and is not capable of supporting it for
1718   any resource.
1722<section title="502 Bad Gateway" anchor="status.502">
1723  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1724  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1726   The server, while acting as a gateway or proxy, received an invalid
1727   response from the upstream server it accessed in attempting to
1728   fulfill the request.
1732<section title="503 Service Unavailable" anchor="status.503">
1733  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1734  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1736   The server is currently unable to handle the request due to a
1737   temporary overloading or maintenance of the server. The implication
1738   is that this is a temporary condition which will be alleviated after
1739   some delay. If known, the length of the delay &MAY; be indicated in a
1740   Retry-After header. If no Retry-After is given, the client &SHOULD;
1741   handle the response as it would for a 500 response.
1742  <list><t>
1743      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1744      server must use it when becoming overloaded. Some servers may wish
1745      to simply refuse the connection.
1746  </t></list>
1750<section title="504 Gateway Timeout" anchor="status.504">
1751  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1752  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1754   The server, while acting as a gateway or proxy, did not receive a
1755   timely response from the upstream server specified by the URI (e.g.
1756   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1757   to access in attempting to complete the request.
1758  <list><t>
1759      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1760      return 400 or 500 when DNS lookups time out.
1761  </t></list>
1765<section title="505 HTTP Version Not Supported" anchor="status.505">
1766  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1767  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1769   The server does not support, or refuses to support, the protocol
1770   version that was used in the request message. The server is
1771   indicating that it is unable or unwilling to complete the request
1772   using the same major version as the client, as described in &http-version;,
1773   other than with this error message. The response &SHOULD; contain
1774   an entity describing why that version is not supported and what other
1775   protocols are supported by that server.
1783<section title="Header Field Definitions" anchor="header.fields">
1785   This section defines the syntax and semantics of HTTP/1.1 header fields
1786   related to request and response semantics.
1789   For entity-header fields, both sender and recipient refer to either the
1790   client or the server, depending on who sends and who receives the entity.
1793<section title="Allow" anchor="header.allow">
1794  <iref primary="true" item="Allow header" x:for-anchor=""/>
1795  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1796  <x:anchor-alias value="Allow"/>
1797  <x:anchor-alias value="Allow-v"/>
1799      The response-header field "Allow" lists the set of methods advertised as
1800      supported by the resource identified by the Request-URI. The purpose of
1801      this field is strictly to inform the recipient of valid methods
1802      associated with the resource. An Allow header field &MUST; be
1803      present in a 405 (Method Not Allowed) response.
1805<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1806  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1807  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1810      Example of use:
1812<figure><artwork type="example">
1813  Allow: GET, HEAD, PUT
1816      The actual set of allowed methods is defined
1817      by the origin server at the time of each request.
1820      A proxy &MUST-NOT; modify the Allow header field even if it does not
1821      understand all the methods specified, since the user agent might
1822      have other means of communicating with the origin server.
1826<section title="Expect" anchor="header.expect">
1827  <iref primary="true" item="Expect header" x:for-anchor=""/>
1828  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1829  <x:anchor-alias value="Expect"/>
1830  <x:anchor-alias value="Expect-v"/>
1831  <x:anchor-alias value="expectation"/>
1832  <x:anchor-alias value="expectation-extension"/>
1833  <x:anchor-alias value="expect-params"/>
1835   The request-header field "Expect" is used to indicate that particular
1836   server behaviors are required by the client.
1838<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="Expect-v"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
1839  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1840  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1842  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1843  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1844                           *<x:ref>expect-params</x:ref> ]
1845  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1848   A server that does not understand or is unable to comply with any of
1849   the expectation values in the Expect field of a request &MUST; respond
1850   with appropriate error status. The server &MUST; respond with a 417
1851   (Expectation Failed) status if any of the expectations cannot be met
1852   or, if there are other problems with the request, some other 4xx
1853   status.
1856   This header field is defined with extensible syntax to allow for
1857   future extensions. If a server receives a request containing an
1858   Expect field that includes an expectation-extension that it does not
1859   support, it &MUST; respond with a 417 (Expectation Failed) status.
1862   Comparison of expectation values is case-insensitive for unquoted
1863   tokens (including the 100-continue token), and is case-sensitive for
1864   quoted-string expectation-extensions.
1867   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1868   return a 417 (Expectation Failed) status if it receives a request
1869   with an expectation that it cannot meet. However, the Expect
1870   request-header itself is end-to-end; it &MUST; be forwarded if the
1871   request is forwarded.
1874   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1875   Expect header.
1878   See &use100; for the use of the 100 (Continue) status.
1882<section title="From" anchor="header.from">
1883  <iref primary="true" item="From header" x:for-anchor=""/>
1884  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1885  <x:anchor-alias value="From"/>
1886  <x:anchor-alias value="From-v"/>
1887  <x:anchor-alias value="mailbox"/>
1889   The request-header field "From", if given, &SHOULD; contain an Internet
1890   e-mail address for the human user who controls the requesting user
1891   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1892   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
1894<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
1895  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
1896  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
1898  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
1901   An example is:
1903<figure><artwork type="example">
1904  From:
1907   This header field &MAY; be used for logging purposes and as a means for
1908   identifying the source of invalid or unwanted requests. It &SHOULD-NOT;
1909   be used as an insecure form of access protection. The interpretation
1910   of this field is that the request is being performed on behalf of the
1911   person given, who accepts responsibility for the method performed. In
1912   particular, robot agents &SHOULD; include this header so that the
1913   person responsible for running the robot can be contacted if problems
1914   occur on the receiving end.
1917   The Internet e-mail address in this field &MAY; be separate from the
1918   Internet host which issued the request. For example, when a request
1919   is passed through a proxy the original issuer's address &SHOULD; be
1920   used.
1923   The client &SHOULD-NOT;  send the From header field without the user's
1924   approval, as it might conflict with the user's privacy interests or
1925   their site's security policy. It is strongly recommended that the
1926   user be able to disable, enable, and modify the value of this field
1927   at any time prior to a request.
1931<section title="Location" anchor="header.location">
1932  <iref primary="true" item="Location header" x:for-anchor=""/>
1933  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1934  <x:anchor-alias value="Location"/>
1935  <x:anchor-alias value="Location-v"/>
1937   The response-header field "Location" is used for the identification of a
1938   new resource or to redirect the recipient to a location other than the
1939   Request-URI for completion of the request.  For 201 (Created)
1940   responses, the Location is that of the new resource which was created
1941   by the request. For 3xx responses, the location &SHOULD; indicate the
1942   server's preferred URI for automatic redirection to the resource. The
1943   field value consists of a single absolute URI.
1945<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
1946  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
1947  <x:ref>Location-v</x:ref>     = <x:ref>absolute-URI</x:ref> [ "#" <x:ref>fragment</x:ref> ]
1950   An example is:
1952<figure><artwork type="example">
1953  Location:
1956  <list><t>
1957      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1958      from Location in that the Content-Location identifies the original
1959      location of the entity enclosed in the response. It is therefore
1960      possible for a response to contain header fields for both Location
1961      and Content-Location.
1962  </t></list>
1965   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1966   <list style="symbols">
1967      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1968      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1969      <t>With 305 Use Proxy.</t>
1970   </list>
1974<section title="Max-Forwards" anchor="header.max-forwards">
1975  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1976  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1977  <x:anchor-alias value="Max-Forwards"/>
1978  <x:anchor-alias value="Max-Forwards-v"/>
1980   The request-header "Max-Forwards" field provides a mechanism with the
1981   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
1982   number of proxies or gateways that can forward the request to the
1983   next inbound server. This can be useful when the client is attempting
1984   to trace a request chain which appears to be failing or looping in
1985   mid-chain.
1987<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
1988  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
1989  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
1992   The Max-Forwards value is a decimal integer indicating the remaining
1993   number of times this request message may be forwarded.
1996   Each proxy or gateway recipient of a TRACE or OPTIONS request
1997   containing a Max-Forwards header field &MUST; check and update its
1998   value prior to forwarding the request. If the received value is zero
1999   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2000   respond as the final recipient. If the received Max-Forwards value is
2001   greater than zero, then the forwarded message &MUST; contain an updated
2002   Max-Forwards field with a value decremented by one (1).
2005   The Max-Forwards header field &MAY; be ignored for all other methods
2006   defined by this specification and for any extension methods for which
2007   it is not explicitly referred to as part of that method definition.
2011<section title="Referer" anchor="header.referer">
2012  <iref primary="true" item="Referer header" x:for-anchor=""/>
2013  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2014  <x:anchor-alias value="Referer"/>
2015  <x:anchor-alias value="Referer-v"/>
2017   The request-header field "Referer" [sic] allows the client to specify,
2018   for the server's benefit, the address (URI) of the resource from
2019   which the Request-URI was obtained (the "referrer", although the
2020   header field is misspelled.) The Referer request-header allows a
2021   server to generate lists of back-links to resources for interest,
2022   logging, optimized caching, etc. It also allows obsolete or mistyped
2023   links to be traced for maintenance. The Referer field &MUST-NOT; be
2024   sent if the Request-URI was obtained from a source that does not have
2025   its own URI, such as input from the user keyboard.
2027<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2028  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2029  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>relativeURI</x:ref>
2032   Example:
2034<figure><artwork type="example">
2035  Referer:
2038   If the field value is a relative URI, it &SHOULD; be interpreted
2039   relative to the Request-URI. The URI &MUST-NOT; include a fragment. See
2040   <xref target=""/> for security considerations.
2044<section title="Retry-After" anchor="header.retry-after">
2045  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2046  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2047  <x:anchor-alias value="Retry-After"/>
2048  <x:anchor-alias value="Retry-After-v"/>
2050   The response-header "Retry-After" field can be used with a 503 (Service
2051   Unavailable) response to indicate how long the service is expected to
2052   be unavailable to the requesting client. This field &MAY; also be used
2053   with any 3xx (Redirection) response to indicate the minimum time the
2054   user-agent is asked wait before issuing the redirected request. The
2055   value of this field can be either an HTTP-date or an integer number
2056   of seconds (in decimal) after the time of the response.
2058<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2059  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2060  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2062<t anchor="">
2063  <x:anchor-alias value="delta-seconds"/>
2064   Time spans are non-negative decimal integers, representing time in
2065   seconds.
2067<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2068  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2071   Two examples of its use are
2073<figure><artwork type="example">
2074  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2075  Retry-After: 120
2078   In the latter example, the delay is 2 minutes.
2082<section title="Server" anchor="header.server">
2083  <iref primary="true" item="Server header" x:for-anchor=""/>
2084  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2085  <x:anchor-alias value="Server"/>
2086  <x:anchor-alias value="Server-v"/>
2088   The response-header field "Server" contains information about the
2089   software used by the origin server to handle the request. The field
2090   can contain multiple product tokens (&product-tokens;) and comments
2091   identifying the server and any significant subproducts. The product
2092   tokens are listed in order of their significance for identifying the
2093   application.
2095<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2096  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2097  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2098                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2101   Example:
2103<figure><artwork type="example">
2104  Server: CERN/3.0 libwww/2.17
2107   If the response is being forwarded through a proxy, the proxy
2108   application &MUST-NOT; modify the Server response-header. Instead, it
2109   &MUST; include a Via field (as described in &header-via;).
2110  <list><t>
2111      <x:h>Note:</x:h> Revealing the specific software version of the server might
2112      allow the server machine to become more vulnerable to attacks
2113      against software that is known to contain security holes. Server
2114      implementors are encouraged to make this field a configurable
2115      option.
2116  </t></list>
2120<section title="User-Agent" anchor="header.user-agent">
2121  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2122  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2123  <x:anchor-alias value="User-Agent"/>
2124  <x:anchor-alias value="User-Agent-v"/>
2126   The request-header field "User-Agent" contains information about the
2127   user agent originating the request. This is for statistical purposes,
2128   the tracing of protocol violations, and automated recognition of user
2129   agents for the sake of tailoring responses to avoid particular user
2130   agent limitations. User agents &SHOULD; include this field with
2131   requests. The field can contain multiple product tokens (&product-tokens;)
2132   and comments identifying the agent and any subproducts which form a
2133   significant part of the user agent. By convention, the product tokens
2134   are listed in order of their significance for identifying the
2135   application.
2137<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2138  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2139  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2140                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2143   Example:
2145<figure><artwork type="example">
2146  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2152<section title="IANA Considerations" anchor="IANA.considerations">
2154<section title="Method Registry" anchor="method.registration">
2156  The registration procedure for HTTP Methods is defined by
2157  <xref target="method.registry"/> of this document.
2160   The HTTP Method Registry located at <eref target=""/>
2161   should be populated with the registrations below:
2163<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2164<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2165   <ttcol>Method</ttcol>
2166   <ttcol>Safe</ttcol>
2167   <ttcol>Reference</ttcol>
2168   <c>CONNECT</c>
2169   <c>no</c>
2170   <c>
2171      <xref target="CONNECT"/>
2172   </c>
2173   <c>DELETE</c>
2174   <c>no</c>
2175   <c>
2176      <xref target="DELETE"/>
2177   </c>
2178   <c>GET</c>
2179   <c>yes</c>
2180   <c>
2181      <xref target="GET"/>
2182   </c>
2183   <c>HEAD</c>
2184   <c>yes</c>
2185   <c>
2186      <xref target="HEAD"/>
2187   </c>
2188   <c>OPTIONS</c>
2189   <c>yes</c>
2190   <c>
2191      <xref target="OPTIONS"/>
2192   </c>
2193   <c>POST</c>
2194   <c>no</c>
2195   <c>
2196      <xref target="POST"/>
2197   </c>
2198   <c>PUT</c>
2199   <c>no</c>
2200   <c>
2201      <xref target="PUT"/>
2202   </c>
2203   <c>TRACE</c>
2204   <c>yes</c>
2205   <c>
2206      <xref target="TRACE"/>
2207   </c>
2212<section title="Status Code Registry" anchor="status.code.registration">
2214   The registration procedure for HTTP Status Codes -- previously defined
2215   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2216   by <xref target="status.code.registry"/> of this document.
2219   The HTTP Status Code Registry located at <eref target=""/>
2220   should be updated with the registrations below:
2222<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2223<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2224   <ttcol>Value</ttcol>
2225   <ttcol>Description</ttcol>
2226   <ttcol>Reference</ttcol>
2227   <c>100</c>
2228   <c>Continue</c>
2229   <c>
2230      <xref target="status.100"/>
2231   </c>
2232   <c>101</c>
2233   <c>Switching Protocols</c>
2234   <c>
2235      <xref target="status.101"/>
2236   </c>
2237   <c>200</c>
2238   <c>OK</c>
2239   <c>
2240      <xref target="status.200"/>
2241   </c>
2242   <c>201</c>
2243   <c>Created</c>
2244   <c>
2245      <xref target="status.201"/>
2246   </c>
2247   <c>202</c>
2248   <c>Accepted</c>
2249   <c>
2250      <xref target="status.202"/>
2251   </c>
2252   <c>203</c>
2253   <c>Non-Authoritative Information</c>
2254   <c>
2255      <xref target="status.203"/>
2256   </c>
2257   <c>204</c>
2258   <c>No Content</c>
2259   <c>
2260      <xref target="status.204"/>
2261   </c>
2262   <c>205</c>
2263   <c>Reset Content</c>
2264   <c>
2265      <xref target="status.205"/>
2266   </c>
2267   <c>206</c>
2268   <c>Partial Content</c>
2269   <c>
2270      <xref target="status.206"/>
2271   </c>
2272   <c>300</c>
2273   <c>Multiple Choices</c>
2274   <c>
2275      <xref target="status.300"/>
2276   </c>
2277   <c>301</c>
2278   <c>Moved Permanently</c>
2279   <c>
2280      <xref target="status.301"/>
2281   </c>
2282   <c>302</c>
2283   <c>Found</c>
2284   <c>
2285      <xref target="status.302"/>
2286   </c>
2287   <c>303</c>
2288   <c>See Other</c>
2289   <c>
2290      <xref target="status.303"/>
2291   </c>
2292   <c>304</c>
2293   <c>Not Modified</c>
2294   <c>
2295      <xref target="status.304"/>
2296   </c>
2297   <c>305</c>
2298   <c>Use Proxy</c>
2299   <c>
2300      <xref target="status.305"/>
2301   </c>
2302   <c>306</c>
2303   <c>(Unused)</c>
2304   <c>
2305      <xref target="status.306"/>
2306   </c>
2307   <c>307</c>
2308   <c>Temporary Redirect</c>
2309   <c>
2310      <xref target="status.307"/>
2311   </c>
2312   <c>400</c>
2313   <c>Bad Request</c>
2314   <c>
2315      <xref target="status.400"/>
2316   </c>
2317   <c>401</c>
2318   <c>Unauthorized</c>
2319   <c>
2320      <xref target="status.401"/>
2321   </c>
2322   <c>402</c>
2323   <c>Payment Required</c>
2324   <c>
2325      <xref target="status.402"/>
2326   </c>
2327   <c>403</c>
2328   <c>Forbidden</c>
2329   <c>
2330      <xref target="status.403"/>
2331   </c>
2332   <c>404</c>
2333   <c>Not Found</c>
2334   <c>
2335      <xref target="status.404"/>
2336   </c>
2337   <c>405</c>
2338   <c>Method Not Allowed</c>
2339   <c>
2340      <xref target="status.405"/>
2341   </c>
2342   <c>406</c>
2343   <c>Not Acceptable</c>
2344   <c>
2345      <xref target="status.406"/>
2346   </c>
2347   <c>407</c>
2348   <c>Proxy Authentication Required</c>
2349   <c>
2350      <xref target="status.407"/>
2351   </c>
2352   <c>408</c>
2353   <c>Request Timeout</c>
2354   <c>
2355      <xref target="status.408"/>
2356   </c>
2357   <c>409</c>
2358   <c>Conflict</c>
2359   <c>
2360      <xref target="status.409"/>
2361   </c>
2362   <c>410</c>
2363   <c>Gone</c>
2364   <c>
2365      <xref target="status.410"/>
2366   </c>
2367   <c>411</c>
2368   <c>Length Required</c>
2369   <c>
2370      <xref target="status.411"/>
2371   </c>
2372   <c>412</c>
2373   <c>Precondition Failed</c>
2374   <c>
2375      <xref target="status.412"/>
2376   </c>
2377   <c>413</c>
2378   <c>Request Entity Too Large</c>
2379   <c>
2380      <xref target="status.413"/>
2381   </c>
2382   <c>414</c>
2383   <c>Request-URI Too Long</c>
2384   <c>
2385      <xref target="status.414"/>
2386   </c>
2387   <c>415</c>
2388   <c>Unsupported Media Type</c>
2389   <c>
2390      <xref target="status.415"/>
2391   </c>
2392   <c>416</c>
2393   <c>Requested Range Not Satisfiable</c>
2394   <c>
2395      <xref target="status.416"/>
2396   </c>
2397   <c>417</c>
2398   <c>Expectation Failed</c>
2399   <c>
2400      <xref target="status.417"/>
2401   </c>
2402   <c>500</c>
2403   <c>Internal Server Error</c>
2404   <c>
2405      <xref target="status.500"/>
2406   </c>
2407   <c>501</c>
2408   <c>Not Implemented</c>
2409   <c>
2410      <xref target="status.501"/>
2411   </c>
2412   <c>502</c>
2413   <c>Bad Gateway</c>
2414   <c>
2415      <xref target="status.502"/>
2416   </c>
2417   <c>503</c>
2418   <c>Service Unavailable</c>
2419   <c>
2420      <xref target="status.503"/>
2421   </c>
2422   <c>504</c>
2423   <c>Gateway Timeout</c>
2424   <c>
2425      <xref target="status.504"/>
2426   </c>
2427   <c>505</c>
2428   <c>HTTP Version Not Supported</c>
2429   <c>
2430      <xref target="status.505"/>
2431   </c>
2435<section title="Message Header Registration" anchor="message.header.registration">
2437   The Message Header Registry located at <eref target=""/> should be updated
2438   with the permanent registrations below (see <xref target="RFC3864"/>):
2440<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2441<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2442   <ttcol>Header Field Name</ttcol>
2443   <ttcol>Protocol</ttcol>
2444   <ttcol>Status</ttcol>
2445   <ttcol>Reference</ttcol>
2446   <c>Allow</c>
2447   <c>http</c>
2448   <c>standard</c>
2449   <c>
2450      <xref target="header.allow"/>
2451   </c>
2452   <c>Expect</c>
2453   <c>http</c>
2454   <c>standard</c>
2455   <c>
2456      <xref target="header.expect"/>
2457   </c>
2458   <c>From</c>
2459   <c>http</c>
2460   <c>standard</c>
2461   <c>
2462      <xref target="header.from"/>
2463   </c>
2464   <c>Location</c>
2465   <c>http</c>
2466   <c>standard</c>
2467   <c>
2468      <xref target="header.location"/>
2469   </c>
2470   <c>Max-Forwards</c>
2471   <c>http</c>
2472   <c>standard</c>
2473   <c>
2474      <xref target="header.max-forwards"/>
2475   </c>
2476   <c>Referer</c>
2477   <c>http</c>
2478   <c>standard</c>
2479   <c>
2480      <xref target="header.referer"/>
2481   </c>
2482   <c>Retry-After</c>
2483   <c>http</c>
2484   <c>standard</c>
2485   <c>
2486      <xref target="header.retry-after"/>
2487   </c>
2488   <c>Server</c>
2489   <c>http</c>
2490   <c>standard</c>
2491   <c>
2492      <xref target="header.server"/>
2493   </c>
2494   <c>User-Agent</c>
2495   <c>http</c>
2496   <c>standard</c>
2497   <c>
2498      <xref target="header.user-agent"/>
2499   </c>
2503   The change controller is: "IETF ( - Internet Engineering Task Force".
2508<section title="Security Considerations" anchor="security.considerations">
2510   This section is meant to inform application developers, information
2511   providers, and users of the security limitations in HTTP/1.1 as
2512   described by this document. The discussion does not include
2513   definitive solutions to the problems revealed, though it does make
2514   some suggestions for reducing security risks.
2517<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2519   Like any generic data transfer protocol, HTTP cannot regulate the
2520   content of the data that is transferred, nor is there any a priori
2521   method of determining the sensitivity of any particular piece of
2522   information within the context of any given request. Therefore,
2523   applications &SHOULD; supply as much control over this information as
2524   possible to the provider of that information. Four header fields are
2525   worth special mention in this context: Server, Via, Referer and From.
2528   Revealing the specific software version of the server might allow the
2529   server machine to become more vulnerable to attacks against software
2530   that is known to contain security holes. Implementors &SHOULD; make the
2531   Server header field a configurable option.
2534   Proxies which serve as a portal through a network firewall &SHOULD;
2535   take special precautions regarding the transfer of header information
2536   that identifies the hosts behind the firewall. In particular, they
2537   &SHOULD; remove, or replace with sanitized versions, any Via fields
2538   generated behind the firewall.
2541   The Referer header allows reading patterns to be studied and reverse
2542   links drawn. Although it can be very useful, its power can be abused
2543   if user details are not separated from the information contained in
2544   the Referer. Even when the personal information has been removed, the
2545   Referer header might indicate a private document's URI whose
2546   publication would be inappropriate.
2549   The information sent in the From field might conflict with the user's
2550   privacy interests or their site's security policy, and hence it
2551   &SHOULD-NOT;  be transmitted without the user being able to disable,
2552   enable, and modify the contents of the field. The user &MUST; be able
2553   to set the contents of this field within a user preference or
2554   application defaults configuration.
2557   We suggest, though do not require, that a convenient toggle interface
2558   be provided for the user to enable or disable the sending of From and
2559   Referer information.
2562   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2563   fields can sometimes be used to determine that a specific client or
2564   server have a particular security hole which might be exploited.
2565   Unfortunately, this same information is often used for other valuable
2566   purposes for which HTTP currently has no better mechanism.
2570<section title="Encoding Sensitive Information in URIs" anchor="">
2572   Because the source of a link might be private information or might
2573   reveal an otherwise private information source, it is strongly
2574   recommended that the user be able to select whether or not the
2575   Referer field is sent. For example, a browser client could have a
2576   toggle switch for browsing openly/anonymously, which would
2577   respectively enable/disable the sending of Referer and From
2578   information.
2581   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2582   HTTP request if the referring page was transferred with a secure
2583   protocol.
2586   Authors of services should not use
2587   GET-based forms for the submission of sensitive data because that
2588   data will be encoded in the Request-URI. Many existing
2589   servers, proxies, and user agents log or display the Request-URI in
2590   places where it might be visible to third parties. Such services can
2591   use POST-based form submission instead.
2595<section title="Location Headers and Spoofing" anchor="location.spoofing">
2597   If a single server supports multiple organizations that do not trust
2598   one another, then it &MUST; check the values of Location and Content-Location
2599   headers in responses that are generated under control of
2600   said organizations to make sure that they do not attempt to
2601   invalidate resources over which they have no authority.
2607<section title="Acknowledgments" anchor="ack">
2612<references title="Normative References">
2614<reference anchor="Part1">
2615  <front>
2616    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2617    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2618      <organization abbrev="Day Software">Day Software</organization>
2619      <address><email></email></address>
2620    </author>
2621    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2622      <organization>One Laptop per Child</organization>
2623      <address><email></email></address>
2624    </author>
2625    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2626      <organization abbrev="HP">Hewlett-Packard Company</organization>
2627      <address><email></email></address>
2628    </author>
2629    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2630      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2631      <address><email></email></address>
2632    </author>
2633    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2634      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2635      <address><email></email></address>
2636    </author>
2637    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2638      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2639      <address><email></email></address>
2640    </author>
2641    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2642      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2643      <address><email></email></address>
2644    </author>
2645    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2646      <organization abbrev="W3C">World Wide Web Consortium</organization>
2647      <address><email></email></address>
2648    </author>
2649    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2650      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2651      <address><email></email></address>
2652    </author>
2653    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2654  </front>
2655  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2656  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2659<reference anchor="Part3">
2660  <front>
2661    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2662    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2663      <organization abbrev="Day Software">Day Software</organization>
2664      <address><email></email></address>
2665    </author>
2666    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2667      <organization>One Laptop per Child</organization>
2668      <address><email></email></address>
2669    </author>
2670    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2671      <organization abbrev="HP">Hewlett-Packard Company</organization>
2672      <address><email></email></address>
2673    </author>
2674    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2675      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2676      <address><email></email></address>
2677    </author>
2678    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2679      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2680      <address><email></email></address>
2681    </author>
2682    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2683      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2684      <address><email></email></address>
2685    </author>
2686    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2687      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2688      <address><email></email></address>
2689    </author>
2690    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2691      <organization abbrev="W3C">World Wide Web Consortium</organization>
2692      <address><email></email></address>
2693    </author>
2694    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2695      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2696      <address><email></email></address>
2697    </author>
2698    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2699  </front>
2700  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2701  <x:source href="p3-payload.xml" basename="p3-payload"/>
2704<reference anchor="Part4">
2705  <front>
2706    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2707    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2708      <organization abbrev="Day Software">Day Software</organization>
2709      <address><email></email></address>
2710    </author>
2711    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2712      <organization>One Laptop per Child</organization>
2713      <address><email></email></address>
2714    </author>
2715    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2716      <organization abbrev="HP">Hewlett-Packard Company</organization>
2717      <address><email></email></address>
2718    </author>
2719    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2720      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2721      <address><email></email></address>
2722    </author>
2723    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2724      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2725      <address><email></email></address>
2726    </author>
2727    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2728      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2729      <address><email></email></address>
2730    </author>
2731    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2732      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2733      <address><email></email></address>
2734    </author>
2735    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2736      <organization abbrev="W3C">World Wide Web Consortium</organization>
2737      <address><email></email></address>
2738    </author>
2739    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2740      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2741      <address><email></email></address>
2742    </author>
2743    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2744  </front>
2745  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2746  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2749<reference anchor="Part5">
2750  <front>
2751    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2752    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2753      <organization abbrev="Day Software">Day Software</organization>
2754      <address><email></email></address>
2755    </author>
2756    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2757      <organization>One Laptop per Child</organization>
2758      <address><email></email></address>
2759    </author>
2760    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2761      <organization abbrev="HP">Hewlett-Packard Company</organization>
2762      <address><email></email></address>
2763    </author>
2764    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2765      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2766      <address><email></email></address>
2767    </author>
2768    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2769      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2770      <address><email></email></address>
2771    </author>
2772    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2773      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2774      <address><email></email></address>
2775    </author>
2776    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2777      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2778      <address><email></email></address>
2779    </author>
2780    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2781      <organization abbrev="W3C">World Wide Web Consortium</organization>
2782      <address><email></email></address>
2783    </author>
2784    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2785      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2786      <address><email></email></address>
2787    </author>
2788    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2789  </front>
2790  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2791  <x:source href="p5-range.xml" basename="p5-range"/>
2794<reference anchor="Part6">
2795  <front>
2796    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2797    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2798      <organization abbrev="Day Software">Day Software</organization>
2799      <address><email></email></address>
2800    </author>
2801    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2802      <organization>One Laptop per Child</organization>
2803      <address><email></email></address>
2804    </author>
2805    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2806      <organization abbrev="HP">Hewlett-Packard Company</organization>
2807      <address><email></email></address>
2808    </author>
2809    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2810      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2811      <address><email></email></address>
2812    </author>
2813    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2814      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2815      <address><email></email></address>
2816    </author>
2817    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2818      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2819      <address><email></email></address>
2820    </author>
2821    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2822      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2823      <address><email></email></address>
2824    </author>
2825    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2826      <organization abbrev="W3C">World Wide Web Consortium</organization>
2827      <address><email></email></address>
2828    </author>
2829    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2830      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2831      <address><email></email></address>
2832    </author>
2833    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2834  </front>
2835  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2836  <x:source href="p6-cache.xml" basename="p6-cache"/>
2839<reference anchor="Part7">
2840  <front>
2841    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2842    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2843      <organization abbrev="Day Software">Day Software</organization>
2844      <address><email></email></address>
2845    </author>
2846    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2847      <organization>One Laptop per Child</organization>
2848      <address><email></email></address>
2849    </author>
2850    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2851      <organization abbrev="HP">Hewlett-Packard Company</organization>
2852      <address><email></email></address>
2853    </author>
2854    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2855      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2856      <address><email></email></address>
2857    </author>
2858    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2859      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2860      <address><email></email></address>
2861    </author>
2862    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2863      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2864      <address><email></email></address>
2865    </author>
2866    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2867      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2868      <address><email></email></address>
2869    </author>
2870    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2871      <organization abbrev="W3C">World Wide Web Consortium</organization>
2872      <address><email></email></address>
2873    </author>
2874    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2875      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2876      <address><email></email></address>
2877    </author>
2878    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2879  </front>
2880  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2881  <x:source href="p7-auth.xml" basename="p7-auth"/>
2884<reference anchor="RFC2119">
2885  <front>
2886    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2887    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2888      <organization>Harvard University</organization>
2889      <address><email></email></address>
2890    </author>
2891    <date month="March" year="1997"/>
2892  </front>
2893  <seriesInfo name="BCP" value="14"/>
2894  <seriesInfo name="RFC" value="2119"/>
2899<references title="Informative References">
2901<reference anchor="RFC1945">
2902  <front>
2903    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2904    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2905      <organization>MIT, Laboratory for Computer Science</organization>
2906      <address><email></email></address>
2907    </author>
2908    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2909      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2910      <address><email></email></address>
2911    </author>
2912    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2913      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2914      <address><email></email></address>
2915    </author>
2916    <date month="May" year="1996"/>
2917  </front>
2918  <seriesInfo name="RFC" value="1945"/>
2921<reference anchor="RFC2068">
2922  <front>
2923    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2924    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2925      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2926      <address><email></email></address>
2927    </author>
2928    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2929      <organization>MIT Laboratory for Computer Science</organization>
2930      <address><email></email></address>
2931    </author>
2932    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2933      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2934      <address><email></email></address>
2935    </author>
2936    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2937      <organization>MIT Laboratory for Computer Science</organization>
2938      <address><email></email></address>
2939    </author>
2940    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2941      <organization>MIT Laboratory for Computer Science</organization>
2942      <address><email></email></address>
2943    </author>
2944    <date month="January" year="1997"/>
2945  </front>
2946  <seriesInfo name="RFC" value="2068"/>
2949<reference anchor="RFC2616">
2950  <front>
2951    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2952    <author initials="R." surname="Fielding" fullname="R. Fielding">
2953      <organization>University of California, Irvine</organization>
2954      <address><email></email></address>
2955    </author>
2956    <author initials="J." surname="Gettys" fullname="J. Gettys">
2957      <organization>W3C</organization>
2958      <address><email></email></address>
2959    </author>
2960    <author initials="J." surname="Mogul" fullname="J. Mogul">
2961      <organization>Compaq Computer Corporation</organization>
2962      <address><email></email></address>
2963    </author>
2964    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2965      <organization>MIT Laboratory for Computer Science</organization>
2966      <address><email></email></address>
2967    </author>
2968    <author initials="L." surname="Masinter" fullname="L. Masinter">
2969      <organization>Xerox Corporation</organization>
2970      <address><email></email></address>
2971    </author>
2972    <author initials="P." surname="Leach" fullname="P. Leach">
2973      <organization>Microsoft Corporation</organization>
2974      <address><email></email></address>
2975    </author>
2976    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2977      <organization>W3C</organization>
2978      <address><email></email></address>
2979    </author>
2980    <date month="June" year="1999"/>
2981  </front>
2982  <seriesInfo name="RFC" value="2616"/>
2985<reference anchor='RFC2817'>
2986  <front>
2987    <title>Upgrading to TLS Within HTTP/1.1</title>
2988    <author initials='R.' surname='Khare' fullname='R. Khare'>
2989      <organization>4K Associates / UC Irvine</organization>
2990      <address><email></email></address>
2991    </author>
2992    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
2993      <organization>Agranat Systems, Inc.</organization>
2994      <address><email></email></address>
2995    </author>
2996    <date year='2000' month='May' />
2997  </front>
2998  <seriesInfo name='RFC' value='2817' />
3001<reference anchor='RFC3864'>
3002  <front>
3003    <title>Registration Procedures for Message Header Fields</title>
3004    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3005      <organization>Nine by Nine</organization>
3006      <address><email></email></address>
3007    </author>
3008    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3009      <organization>BEA Systems</organization>
3010      <address><email></email></address>
3011    </author>
3012    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3013      <organization>HP Labs</organization>
3014      <address><email></email></address>
3015    </author>
3016    <date year='2004' month='September' />
3017  </front>
3018  <seriesInfo name='BCP' value='90' />
3019  <seriesInfo name='RFC' value='3864' />
3022<reference anchor='RFC5226'>
3023  <front>
3024    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3025    <author initials='T.' surname='Narten' fullname='T. Narten'>
3026      <organization>IBM</organization>
3027      <address><email></email></address>
3028    </author>
3029    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3030      <organization>Google</organization>
3031      <address><email></email></address>
3032    </author>
3033    <date year='2008' month='May' />
3034  </front>
3035  <seriesInfo name='BCP' value='26' />
3036  <seriesInfo name='RFC' value='5226' />
3039<reference anchor="RFC5322">
3040  <front>
3041    <title>Internet Message Format</title>
3042    <author initials="P." surname="Resnick" fullname="P. Resnick">
3043      <organization>Qualcomm Incorporated</organization>
3044    </author>
3045    <date year="2008" month="October"/>
3046  </front>
3047  <seriesInfo name="RFC" value="5322"/>
3052<section title="Compatibility with Previous Versions" anchor="compatibility">
3053<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3055   Clarified which error code should be used for inbound server failures
3056   (e.g. DNS failures). (<xref target="status.504"/>).
3059   201 (Created) had a race that required an Etag be sent when a resource is
3060   first created. (<xref target="status.201"/>).
3063   Rewrite of message transmission requirements to make it much harder
3064   for implementors to get it wrong, as the consequences of errors here
3065   can have significant impact on the Internet, and to deal with the
3066   following problems:
3067  <list style="numbers">
3068      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3069         this was incorrectly placing a requirement on the behavior of
3070         an implementation of a future version of HTTP/1.x</t>
3072      <t>Made it clear that user-agents should retry requests, not
3073         "clients" in general.</t>
3075      <t>Converted requirements for clients to ignore unexpected 100
3076         (Continue) responses, and for proxies to forward 100 responses,
3077         into a general requirement for 1xx responses.</t>
3079      <t>Modified some TCP-specific language, to make it clearer that
3080         non-TCP transports are possible for HTTP.</t>
3082      <t>Require that the origin server &MUST-NOT; wait for the request
3083         body before it sends a required 100 (Continue) response.</t>
3085      <t>Allow, rather than require, a server to omit 100 (Continue) if
3086         it has already seen some of the request body.</t>
3088      <t>Allow servers to defend against denial-of-service attacks and
3089         broken clients.</t>
3090  </list>
3093   This change adds the Expect header and 417 status code.
3096   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3097   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3100   The PATCH<iref item="PATCH method" primary="true"/><iref item="Methods" subitem="PATCH" primary="true"/>, LINK<iref item="LINK method" primary="true"/><iref item="Methods" subitem="LINK" primary="true"/>, UNLINK<iref item="UNLINK method" primary="true"/><iref item="Methods" subitem="UNLINK" primary="true"/> methods were defined but not commonly
3101   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3105<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3107  This document takes over the Status Code Registry, previously defined
3108  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3109  (<xref target="status.code.registry"/>)
3112  Clarify definition of POST.
3113  (<xref target="POST"/>)
3116  Failed to consider that there are
3117  many other request methods that are safe to automatically redirect,
3118  and further that the user agent is able to make that determination
3119  based on the request method semantics.
3120  (Sections <xref format="counter" target="status.301"/>,
3121  <xref format="counter" target="status.302"/> and
3122  <xref format="counter" target="status.307"/>)
3125  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3126  It used to indicate that the requested resource must be accessed through the
3127  proxy given by the Location field. The Location field gave the URI of the
3128  proxy. The recipient was expected to repeat this single request via the proxy.
3129  (<xref target="status.305"/>)
3132  Reclassify Allow header as response header, removing the option to
3133  specify it in a PUT request.
3134  Relax the server requirement on the contents of the Allow header and
3135  remove requirement on clients to always trust the header value.
3136  (<xref target="header.allow"/>)
3139  Correct syntax of Location header to allow fragment,
3140  as referred symbol wasn't what was expected, and add some
3141  clarifications as to when it would not be appropriate.
3142  (<xref target="header.location"/>)
3145  In the description of the Server header, the Via field
3146  was described as a SHOULD. The requirement was and is stated
3147  correctly in the description of the Via header in &header-via;.
3148  (<xref target="header.server"/>)
3154<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3156<section title="Since RFC2616">
3158  Extracted relevant partitions from <xref target="RFC2616"/>.
3162<section title="Since draft-ietf-httpbis-p2-semantics-00">
3164  Closed issues:
3165  <list style="symbols">
3166    <t>
3167      <eref target=""/>:
3168      "Via is a MUST"
3169      (<eref target=""/>)
3170    </t>
3171    <t>
3172      <eref target=""/>:
3173      "Fragments allowed in Location"
3174      (<eref target=""/>)
3175    </t>
3176    <t>
3177      <eref target=""/>:
3178      "Safe Methods vs Redirection"
3179      (<eref target=""/>)
3180    </t>
3181    <t>
3182      <eref target=""/>:
3183      "Revise description of the POST method"
3184      (<eref target=""/>)
3185    </t>
3186    <t>
3187      <eref target=""/>:
3188      "Normative and Informative references"
3189    </t>
3190    <t>
3191      <eref target=""/>:
3192      "RFC2606 Compliance"
3193    </t>
3194    <t>
3195      <eref target=""/>:
3196      "Informative references"
3197    </t>
3198    <t>
3199      <eref target=""/>:
3200      "Redundant cross-references"
3201    </t>
3202  </list>
3205  Other changes:
3206  <list style="symbols">
3207    <t>
3208      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3209    </t>
3210  </list>
3214<section title="Since draft-ietf-httpbis-p2-semantics-01">
3216  Closed issues:
3217  <list style="symbols">
3218    <t>
3219      <eref target=""/>:
3220      "PUT side effects"
3221    </t>
3222    <t>
3223      <eref target=""/>:
3224      "Duplicate Host header requirements"
3225    </t>
3226  </list>
3229  Ongoing work on ABNF conversion (<eref target=""/>):
3230  <list style="symbols">
3231    <t>
3232      Move "Product Tokens" section (back) into Part 1, as "token" is used
3233      in the definition of the Upgrade header.
3234    </t>
3235    <t>
3236      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3237    </t>
3238    <t>
3239      Copy definition of delta-seconds from Part6 instead of referencing it.
3240    </t>
3241  </list>
3245<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3247  Closed issues:
3248  <list style="symbols">
3249    <t>
3250      <eref target=""/>:
3251      "Requiring Allow in 405 responses"
3252    </t>
3253    <t>
3254      <eref target=""/>:
3255      "Status Code Registry"
3256    </t>
3257    <t>
3258      <eref target=""/>:
3259      "Redirection vs. Location"
3260    </t>
3261    <t>
3262      <eref target=""/>:
3263      "Cacheability of 303 response"
3264    </t>
3265    <t>
3266      <eref target=""/>:
3267      "305 Use Proxy"
3268    </t>
3269    <t>
3270      <eref target=""/>:
3271      "Classification for Allow header"
3272    </t>
3273    <t>
3274      <eref target=""/>:
3275      "PUT - 'store under' vs 'store at'"
3276    </t>
3277  </list>
3280  Ongoing work on IANA Message Header Registration (<eref target=""/>):
3281  <list style="symbols">
3282    <t>
3283      Reference RFC 3984, and update header registrations for headers defined
3284      in this document.
3285    </t>
3286  </list>
3289  Ongoing work on ABNF conversion (<eref target=""/>):
3290  <list style="symbols">
3291    <t>
3292      Replace string literals when the string really is case-sensitive (method).
3293    </t>
3294  </list>
3298<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3300  Closed issues:
3301  <list style="symbols">
3302    <t>
3303      <eref target=""/>:
3304      "OPTIONS request bodies"
3305    </t>
3306    <t>
3307      <eref target=""/>:
3308      "Description of CONNECT should refer to RFC2817"
3309    </t>
3310    <t>
3311      <eref target=""/>:
3312      "Location Content-Location reference request/response mixup"
3313    </t>
3314  </list>
3317  Ongoing work on Method Registry (<eref target=""/>):
3318  <list style="symbols">
3319    <t>
3320      Added initial proposal for registration process, plus initial
3321      content (non-HTTP/1.1 methods to be added by a separate specification).
3322    </t>
3323  </list>
3327<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3329  Closed issues:
3330  <list style="symbols">
3331    <t>
3332      <eref target=""/>:
3333      "Content-*"
3334    </t>
3335    <t>
3336      <eref target=""/>:
3337      "RFC 2822 is updated by RFC 5322"
3338    </t>
3339  </list>
3342  Ongoing work on ABNF conversion (<eref target=""/>):
3343  <list style="symbols">
3344    <t>
3345      Use "/" instead of "|" for alternatives.
3346    </t>
3347    <t>
3348      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3349      whitespace ("OWS") and required whitespace ("RWS").
3350    </t>
3351    <t>
3352      Rewrite ABNFs to spell out whitespace rules, factor out
3353      header value format definitions.
3354    </t>
3355  </list>
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