source: draft-ietf-httpbis/latest-roy/p2-semantics.xml @ 348

Last change on this file since 348 was 348, checked in by fielding@…, 14 years ago

replace xref to general-syntax with xref to uri

  • Property svn:eol-style set to native
File size: 141.9 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>">
14  <!ENTITY ID-VERSION "latest">
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;"/>
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"/>
296  This specification uses the ABNF syntax defined in &notation-abnf; and
297  the core rules defined in &basic-rules;:
298  <cref anchor="abnf.dep">ABNF syntax and basic rules will be adopted from RFC 5234, see
299  <eref target=""/>.</cref>
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;
309<t anchor="abnf.dependencies">
310  <x:anchor-alias value="absoluteURI"/>
311  <x:anchor-alias value="Accept"/>
312  <x:anchor-alias value="Accept-Charset"/>
313  <x:anchor-alias value="Accept-Encoding"/>
314  <x:anchor-alias value="Accept-Language"/>
315  <x:anchor-alias value="Accept-Ranges"/>
316  <x:anchor-alias value="Age"/>
317  <x:anchor-alias value="Authorization"/>
318  <x:anchor-alias value="ETag"/>
319  <x:anchor-alias value="fragment"/>
320  <x:anchor-alias value="Host"/>
321  <x:anchor-alias value="HTTP-date"/>
322  <x:anchor-alias value="If-Match"/>
323  <x:anchor-alias value="If-Modified-Since"/>
324  <x:anchor-alias value="If-None-Match"/>
325  <x:anchor-alias value="If-Range"/>
326  <x:anchor-alias value="If-Unmodified-Since"/>
327  <x:anchor-alias value="product"/>
328  <x:anchor-alias value="Proxy-Authenticate"/>
329  <x:anchor-alias value="Proxy-Authorization"/>
330  <x:anchor-alias value="Range"/>
331  <x:anchor-alias value="relativeURI"/>
332  <x:anchor-alias value="TE"/>
333  <x:anchor-alias value="Vary"/>
334  <x:anchor-alias value="WWW-Authenticate"/>
335  The ABNF rules below are defined in other parts:
337<figure><!--Part1--><artwork type="abnf2616">
338  <x:ref>absoluteURI</x:ref>   = &lt;absoluteURI, defined in &uri;&gt;
339  <x:ref>fragment</x:ref>      = &lt;fragment, defined in &uri;&gt;
340  <x:ref>Host</x:ref>          = &lt;Host, defined in &header-host;&gt;
341  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
342  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
343  <x:ref>relativeURI</x:ref>   = &lt;relativeURI, defined in &uri;&gt;
344  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
346<figure><!--Part3--><artwork type="abnf2616">
347  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
348  <x:ref>Accept-Charset</x:ref> =
349             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
350  <x:ref>Accept-Encoding</x:ref> =
351             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
352  <x:ref>Accept-Language</x:ref> =
353             &lt;Accept-Language, defined in &header-accept-language;&gt;
355<figure><!--Part4--><artwork type="abnf2616">
356  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
357  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
358  <x:ref>If-Modified-Since</x:ref> =
359             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
360  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
361  <x:ref>If-Unmodified-Since</x:ref> =
362             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
364<figure><!--Part5--><artwork type="abnf2616">
365  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
366  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
367  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
369<figure><!--Part6--><artwork type="abnf2616">
370  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
371  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
373<figure><artwork type="abnf2616">
374  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
375  <x:ref>Proxy-Authenticate</x:ref> =
376             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
377  <x:ref>Proxy-Authorization</x:ref> =
378             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
379  <x:ref>WWW-Authenticate</x:ref> =
380             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
384<section title="Method" anchor="method">
385  <x:anchor-alias value="Method"/>
386  <x:anchor-alias value="extension-method"/>
388   The Method  token indicates the method to be performed on the
389   resource identified by the Request-URI. The method is case-sensitive.
391<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
392  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
393                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
394                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
395                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
396                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
397                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
398                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
399                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
400                 / <x:ref>extension-method</x:ref>
401  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
404   The list of methods allowed by a resource can be specified in an
405   Allow header field (<xref target="header.allow"/>). The return code of the response
406   always notifies the client whether a method is currently allowed on a
407   resource, since the set of allowed methods can change dynamically. An
408   origin server &SHOULD; return the status code 405 (Method Not Allowed)
409   if the method is known by the origin server but not allowed for the
410   requested resource, and 501 (Not Implemented) if the method is
411   unrecognized or not implemented by the origin server. The methods GET
412   and HEAD &MUST; be supported by all general-purpose servers. All other
413   methods are &OPTIONAL;; however, if the above methods are implemented,
414   they &MUST; be implemented with the same semantics as those specified
415   in <xref target="method.definitions"/>.
418<section title="Method Registry" anchor="method.registry">
420  The HTTP Method Registry defines the name space for the Method token in the
421  Request line of an HTTP request.
424  Registrations &MUST; include the following fields:
425  <list style="symbols">
426    <t>Method Name (see <xref target="method"/>)</t>
427    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
428    <t>Pointer to specification text</t>
429  </list>
432  Values to be added to this name space are subject to IETF review
433  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
434  new method names should be traceable through statuses of either 'Obsoletes'
435  or 'Updates' to this document.
438  The registry itself is maintained at <eref target=""/>.
443<section title="Request Header Fields" anchor="request.header.fields">
444  <x:anchor-alias value="extension-code"/>
445  <x:anchor-alias value="request-header"/>
447   The request-header fields allow the client to pass additional
448   information about the request, and about the client itself, to the
449   server. These fields act as request modifiers, with semantics
450   equivalent to the parameters on a programming language method
451   invocation.
453<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
454  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
455                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
456                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
457                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
458                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
459                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
460                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
461                 / <x:ref>Host</x:ref>                     ; &header-host;
462                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
463                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
464                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
465                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
466                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
467                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
468                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
469                 / <x:ref>Range</x:ref>                    ; &header-range;
470                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
471                 / <x:ref>TE</x:ref>                       ; &header-te;
472                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
475   Request-header field names can be extended reliably only in
476   combination with a change in the protocol version. However, new or
477   experimental header fields &MAY; be given the semantics of request-header
478   fields if all parties in the communication recognize them to
479   be request-header fields. Unrecognized header fields are treated as
480   entity-header fields.
484<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
485  <x:anchor-alias value="Reason-Phrase"/>
486  <x:anchor-alias value="Status-Code"/>
488   The Status-Code element is a 3-digit integer result code of the
489   attempt to understand and satisfy the request. The status codes listed
490   below are defined in <xref target=""/>.
491   The Reason-Phrase is intended to give a short
492   textual description of the Status-Code. The Status-Code is intended
493   for use by automata and the Reason-Phrase is intended for the human
494   user. The client is not required to examine or display the Reason-Phrase.
497   The individual values of the numeric status codes defined for
498   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
499   presented below. The reason phrases listed here are only
500   recommendations -- they &MAY; be replaced by local equivalents without
501   affecting the protocol.
503<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"/>
504  <x:ref>Status-Code</x:ref>    =
505         "100"  ; <xref target="status.100"/>: Continue
506       / "101"  ; <xref target="status.101"/>: Switching Protocols
507       / "200"  ; <xref target="status.200"/>: OK
508       / "201"  ; <xref target="status.201"/>: Created
509       / "202"  ; <xref target="status.202"/>: Accepted
510       / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
511       / "204"  ; <xref target="status.204"/>: No Content
512       / "205"  ; <xref target="status.205"/>: Reset Content
513       / "206"  ; <xref target="status.206"/>: Partial Content
514       / "300"  ; <xref target="status.300"/>: Multiple Choices
515       / "301"  ; <xref target="status.301"/>: Moved Permanently
516       / "302"  ; <xref target="status.302"/>: Found
517       / "303"  ; <xref target="status.303"/>: See Other
518       / "304"  ; <xref target="status.304"/>: Not Modified
519       / "305"  ; <xref target="status.305"/>: Use Proxy
520       / "307"  ; <xref target="status.307"/>: Temporary Redirect
521       / "400"  ; <xref target="status.400"/>: Bad Request
522       / "401"  ; <xref target="status.401"/>: Unauthorized
523       / "402"  ; <xref target="status.402"/>: Payment Required
524       / "403"  ; <xref target="status.403"/>: Forbidden
525       / "404"  ; <xref target="status.404"/>: Not Found
526       / "405"  ; <xref target="status.405"/>: Method Not Allowed
527       / "406"  ; <xref target="status.406"/>: Not Acceptable
528       / "407"  ; <xref target="status.407"/>: Proxy Authentication Required
529       / "408"  ; <xref target="status.408"/>: Request Time-out
530       / "409"  ; <xref target="status.409"/>: Conflict
531       / "410"  ; <xref target="status.410"/>: Gone
532       / "411"  ; <xref target="status.411"/>: Length Required
533       / "412"  ; <xref target="status.412"/>: Precondition Failed
534       / "413"  ; <xref target="status.413"/>: Request Entity Too Large
535       / "414"  ; <xref target="status.414"/>: Request-URI Too Large
536       / "415"  ; <xref target="status.415"/>: Unsupported Media Type
537       / "416"  ; <xref target="status.416"/>: Requested range not satisfiable
538       / "417"  ; <xref target="status.417"/>: Expectation Failed
539       / "500"  ; <xref target="status.500"/>: Internal Server Error
540       / "501"  ; <xref target="status.501"/>: Not Implemented
541       / "502"  ; <xref target="status.502"/>: Bad Gateway
542       / "503"  ; <xref target="status.503"/>: Service Unavailable
543       / "504"  ; <xref target="status.504"/>: Gateway Time-out
544       / "505"  ; <xref target="status.505"/>: HTTP Version not supported
545       / <x:ref>extension-code</x:ref>
547  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
548  <x:ref>Reason-Phrase</x:ref>  = *&lt;<x:ref>TEXT</x:ref>, excluding <x:ref>CR</x:ref>, <x:ref>LF</x:ref>&gt;
551   HTTP status codes are extensible. HTTP applications are not required
552   to understand the meaning of all registered status codes, though such
553   understanding is obviously desirable. However, applications &MUST;
554   understand the class of any status code, as indicated by the first
555   digit, and treat any unrecognized response as being equivalent to the
556   x00 status code of that class, with the exception that an
557   unrecognized response &MUST-NOT; be cached. For example, if an
558   unrecognized status code of 431 is received by the client, it can
559   safely assume that there was something wrong with its request and
560   treat the response as if it had received a 400 status code. In such
561   cases, user agents &SHOULD; present to the user the entity returned
562   with the response, since that entity is likely to include human-readable
563   information which will explain the unusual status.
566<section title="Status Code Registry" anchor="status.code.registry">
568  The HTTP Status Code Registry defines the name space for the Status-Code
569  token in the Status line of an HTTP response.
572  Values to be added to this name space are subject to IETF review
573  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
574  new status codes should be traceable through statuses of either 'Obsoletes'
575  or 'Updates' to this document.
578  The registry itself is maintained at <eref target=""/>.
584<section title="Response Header Fields" anchor="response.header.fields">
585  <x:anchor-alias value="response-header"/>
587   The response-header fields allow the server to pass additional
588   information about the response which cannot be placed in the Status-Line.
589   These header fields give information about the server and about
590   further access to the resource identified by the Request-URI.
592<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
593  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
594                  / <x:ref>Age</x:ref>                     ; &header-age;
595                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
596                  / <x:ref>ETag</x:ref>                    ; &header-etag;
597                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
598                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
599                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
600                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
601                  / <x:ref>Vary</x:ref>                    ; &header-vary;
602                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
605   Response-header field names can be extended reliably only in
606   combination with a change in the protocol version. However, new or
607   experimental header fields &MAY; be given the semantics of response-header
608   fields if all parties in the communication recognize them to
609   be response-header fields. Unrecognized header fields are treated as
610   entity-header fields.
614<section title="Entity" anchor="entity">
616   Request and Response messages &MAY; transfer an entity if not otherwise
617   restricted by the request method or response status code. An entity
618   consists of entity-header fields and an entity-body, although some
619   responses will only include the entity-headers. HTTP entity-body and
620   entity-header fields are defined in &payload;.
623   An entity-body is only present in a message when a message-body is
624   present, as described in &message-body;. The entity-body is obtained
625   from the message-body by decoding any Transfer-Encoding that might
626   have been applied to ensure safe and proper transfer of the message.
631<section title="Method Definitions" anchor="method.definitions">
633   The set of common methods for HTTP/1.1 is defined below. Although
634   this set can be expanded, additional methods cannot be assumed to
635   share the same semantics for separately extended clients and servers.
638<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
640<section title="Safe Methods" anchor="safe.methods">
641<iref item="Safe Methods" primary="true"/>
643   Implementors should be aware that the software represents the user in
644   their interactions over the Internet, and should be careful to allow
645   the user to be aware of any actions they might take which may have an
646   unexpected significance to themselves or others.
649   In particular, the convention has been established that the GET and
650   HEAD methods &SHOULD-NOT;  have the significance of taking an action
651   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
652   This allows user agents to represent other methods, such as POST, PUT
653   and DELETE, in a special way, so that the user is made aware of the
654   fact that a possibly unsafe action is being requested.
657   Naturally, it is not possible to ensure that the server does not
658   generate side-effects as a result of performing a GET request; in
659   fact, some dynamic resources consider that a feature. The important
660   distinction here is that the user did not request the side-effects,
661   so therefore cannot be held accountable for them.
665<section title="Idempotent Methods" anchor="idempotent.methods">
666<iref item="Idempotent Methods" primary="true"/>
668   Methods can also have the property of "idempotence" in that (aside
669   from error or expiration issues) the side-effects of N &gt; 0 identical
670   requests is the same as for a single request. The methods GET, HEAD,
671   PUT and DELETE share this property. Also, the methods OPTIONS and
672   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
675   However, it is possible that a sequence of several requests is non-idempotent,
676   even if all of the methods executed in that sequence are
677   idempotent. (A sequence is idempotent if a single execution of the
678   entire sequence always yields a result that is not changed by a
679   reexecution of all, or part, of that sequence.) For example, a
680   sequence is non-idempotent if its result depends on a value that is
681   later modified in the same sequence.
684   A sequence that never has side effects is idempotent, by definition
685   (provided that no concurrent operations are being executed on the
686   same set of resources).
691<section title="OPTIONS" anchor="OPTIONS">
692  <rdf:Description>
693    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
694  </rdf:Description>
695  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
696  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
698   The OPTIONS method represents a request for information about the
699   communication options available on the request/response chain
700   identified by the Request-URI. This method allows the client to
701   determine the options and/or requirements associated with a resource,
702   or the capabilities of a server, without implying a resource action
703   or initiating a resource retrieval.
706   Responses to this method are not cacheable.
709   If the OPTIONS request includes an entity-body (as indicated by the
710   presence of Content-Length or Transfer-Encoding), then the media type
711   &MUST; be indicated by a Content-Type field. Although this
712   specification does not define any use for such a body, future
713   extensions to HTTP might use the OPTIONS body to make more detailed
714   queries on the server.
717   If the Request-URI is an asterisk ("*"), the OPTIONS request is
718   intended to apply to the server in general rather than to a specific
719   resource. Since a server's communication options typically depend on
720   the resource, the "*" request is only useful as a "ping" or "no-op"
721   type of method; it does nothing beyond allowing the client to test
722   the capabilities of the server. For example, this can be used to test
723   a proxy for HTTP/1.1 compliance (or lack thereof).
726   If the Request-URI is not an asterisk, the OPTIONS request applies
727   only to the options that are available when communicating with that
728   resource.
731   A 200 response &SHOULD; include any header fields that indicate
732   optional features implemented by the server and applicable to that
733   resource (e.g., Allow), possibly including extensions not defined by
734   this specification. The response body, if any, &SHOULD; also include
735   information about the communication options. The format for such a
736   body is not defined by this specification, but might be defined by
737   future extensions to HTTP. Content negotiation &MAY; be used to select
738   the appropriate response format. If no response body is included, the
739   response &MUST; include a Content-Length field with a field-value of
740   "0".
743   The Max-Forwards request-header field &MAY; be used to target a
744   specific proxy in the request chain. When a proxy receives an OPTIONS
745   request on an absoluteURI for which request forwarding is permitted,
746   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
747   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
748   instead, the proxy &SHOULD; respond with its own communication options.
749   If the Max-Forwards field-value is an integer greater than zero, the
750   proxy &MUST; decrement the field-value when it forwards the request. If
751   no Max-Forwards field is present in the request, then the forwarded
752   request &MUST-NOT; include a Max-Forwards field.
756<section title="GET" anchor="GET">
757  <rdf:Description>
758    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
759  </rdf:Description>
760  <iref primary="true" item="GET method" x:for-anchor=""/>
761  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
763   The GET method means retrieve whatever information (in the form of an
764   entity) is identified by the Request-URI. If the Request-URI refers
765   to a data-producing process, it is the produced data which shall be
766   returned as the entity in the response and not the source text of the
767   process, unless that text happens to be the output of the process.
770   The semantics of the GET method change to a "conditional GET" if the
771   request message includes an If-Modified-Since, If-Unmodified-Since,
772   If-Match, If-None-Match, or If-Range header field. A conditional GET
773   method requests that the entity be transferred only under the
774   circumstances described by the conditional header field(s). The
775   conditional GET method is intended to reduce unnecessary network
776   usage by allowing cached entities to be refreshed without requiring
777   multiple requests or transferring data already held by the client.
780   The semantics of the GET method change to a "partial GET" if the
781   request message includes a Range header field. A partial GET requests
782   that only part of the entity be transferred, as described in &header-range;.
783   The partial GET method is intended to reduce unnecessary
784   network usage by allowing partially-retrieved entities to be
785   completed without transferring data already held by the client.
788   The response to a GET request is cacheable if and only if it meets
789   the requirements for HTTP caching described in &caching;.
792   See <xref target=""/> for security considerations when used for forms.
796<section title="HEAD" anchor="HEAD">
797  <rdf:Description>
798    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
799  </rdf:Description>
800  <iref primary="true" item="HEAD method" x:for-anchor=""/>
801  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
803   The HEAD method is identical to GET except that the server &MUST-NOT;
804   return a message-body in the response. The metainformation contained
805   in the HTTP headers in response to a HEAD request &SHOULD; be identical
806   to the information sent in response to a GET request. This method can
807   be used for obtaining metainformation about the entity implied by the
808   request without transferring the entity-body itself. This method is
809   often used for testing hypertext links for validity, accessibility,
810   and recent modification.
813   The response to a HEAD request &MAY; be cacheable in the sense that the
814   information contained in the response &MAY; be used to update a
815   previously cached entity from that resource. If the new field values
816   indicate that the cached entity differs from the current entity (as
817   would be indicated by a change in Content-Length, Content-MD5, ETag
818   or Last-Modified), then the cache &MUST; treat the cache entry as
819   stale.
823<section title="POST" anchor="POST">
824  <iref primary="true" item="POST method" x:for-anchor=""/>
825  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
827   The POST method is used to request that the origin server accept the
828   entity enclosed in the request as data to be processed by the resource
829   identified by the Request-URI in the Request-Line. POST is designed
830   to allow a uniform method to cover the following functions:
831  <list style="symbols">
832    <t>
833      Annotation of existing resources;
834    </t>
835    <t>
836        Posting a message to a bulletin board, newsgroup, mailing list,
837        or similar group of articles;
838    </t>
839    <t>
840        Providing a block of data, such as the result of submitting a
841        form, to a data-handling process;
842    </t>
843    <t>
844        Extending a database through an append operation.
845    </t>
846  </list>
849   The actual function performed by the POST method is determined by the
850   server and is usually dependent on the Request-URI.
853   The action performed by the POST method might not result in a
854   resource that can be identified by a URI. In this case, either 200
855   (OK) or 204 (No Content) is the appropriate response status,
856   depending on whether or not the response includes an entity that
857   describes the result.
860   If a resource has been created on the origin server, the response
861   &SHOULD; be 201 (Created) and contain an entity which describes the
862   status of the request and refers to the new resource, and a Location
863   header (see <xref target="header.location"/>).
866   Responses to this method are not cacheable, unless the response
867   includes appropriate Cache-Control or Expires header fields. However,
868   the 303 (See Other) response can be used to direct the user agent to
869   retrieve a cacheable resource.
873<section title="PUT" anchor="PUT">
874  <iref primary="true" item="PUT method" x:for-anchor=""/>
875  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
877   The PUT method requests that the enclosed entity be stored at the
878   supplied Request-URI. If the Request-URI refers to an already
879   existing resource, the enclosed entity &SHOULD; be considered as a
880   modified version of the one residing on the origin server. If the
881   Request-URI does not point to an existing resource, and that URI is
882   capable of being defined as a new resource by the requesting user
883   agent, the origin server can create the resource with that URI. If a
884   new resource is created at the Request-URI, the origin server &MUST;
885         inform the user agent
886   via the 201 (Created) response. If an existing resource is modified,
887   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
888   to indicate successful completion of the request. If the resource
889   could not be created or modified with the Request-URI, an appropriate
890   error response &SHOULD; be given that reflects the nature of the
891   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
892   headers (headers starting with the prefix 'Content-') that it does
893   not understand or implement
894   and &MUST; return a 501 (Not Implemented) response in such cases.
897   If the request passes through a cache and the Request-URI identifies
898   one or more currently cached entities, those entries &SHOULD; be
899   treated as stale. Responses to this method are not cacheable.
902   The fundamental difference between the POST and PUT requests is
903   reflected in the different meaning of the Request-URI. The URI in a
904   POST request identifies the resource that will handle the enclosed
905   entity. That resource might be a data-accepting process, a gateway to
906   some other protocol, or a separate entity that accepts annotations.
907   In contrast, the URI in a PUT request identifies the entity enclosed
908   with the request -- the user agent knows what URI is intended and the
909   server &MUST-NOT; attempt to apply the request to some other resource.
910   If the server desires that the request be applied to a different URI,
911   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
912   then make its own decision regarding whether or not to redirect the
913   request.
916   A single resource &MAY; be identified by many different URIs. For
917   example, an article might have a URI for identifying "the current
918   version" which is separate from the URI identifying each particular
919   version. In this case, a PUT request on a general URI might result in
920   several other URIs being defined by the origin server.
923   HTTP/1.1 does not define how a PUT method affects the state of an
924   origin server.
927   Unless otherwise specified for a particular entity-header, the
928   entity-headers in the PUT request &SHOULD; be applied to the resource
929   created or modified by the PUT.
933<section title="DELETE" anchor="DELETE">
934  <iref primary="true" item="DELETE method" x:for-anchor=""/>
935  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
937   The DELETE method requests that the origin server delete the resource
938   identified by the Request-URI. This method &MAY; be overridden by human
939   intervention (or other means) on the origin server. The client cannot
940   be guaranteed that the operation has been carried out, even if the
941   status code returned from the origin server indicates that the action
942   has been completed successfully. However, the server &SHOULD-NOT;
943   indicate success unless, at the time the response is given, it
944   intends to delete the resource or move it to an inaccessible
945   location.
948   A successful response &SHOULD; be 200 (OK) if the response includes an
949   entity describing the status, 202 (Accepted) if the action has not
950   yet been enacted, or 204 (No Content) if the action has been enacted
951   but the response does not include an entity.
954   If the request passes through a cache and the Request-URI identifies
955   one or more currently cached entities, those entries &SHOULD; be
956   treated as stale. Responses to this method are not cacheable.
960<section title="TRACE" anchor="TRACE">
961  <rdf:Description>
962    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
963  </rdf:Description>
964  <iref primary="true" item="TRACE method" x:for-anchor=""/>
965  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
967   The TRACE method is used to invoke a remote, application-layer loop-back
968   of the request message. The final recipient of the request
969   &SHOULD; reflect the message received back to the client as the
970   entity-body of a 200 (OK) response. The final recipient is either the
971   origin server or the first proxy or gateway to receive a Max-Forwards
972   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
973   &MUST-NOT; include an entity.
976   TRACE allows the client to see what is being received at the other
977   end of the request chain and use that data for testing or diagnostic
978   information. The value of the Via header field (&header-via;) is of
979   particular interest, since it acts as a trace of the request chain.
980   Use of the Max-Forwards header field allows the client to limit the
981   length of the request chain, which is useful for testing a chain of
982   proxies forwarding messages in an infinite loop.
985   If the request is valid, the response &SHOULD; contain the entire
986   request message in the entity-body, with a Content-Type of
987   "message/http" (see &media-type-message-http;). Responses to this method
988   &MUST-NOT; be cached.
992<section title="CONNECT" anchor="CONNECT">
993  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
994  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
996   This specification reserves the method name CONNECT for use with a
997   proxy that can dynamically switch to being a tunnel (e.g. SSL
998   tunneling <xref target="RFC2817"/>).
1004<section title="Status Code Definitions" anchor="">
1006   Each Status-Code is described below, including a description of which
1007   method(s) it can follow and any metainformation required in the
1008   response.
1011<section title="Informational 1xx" anchor="status.1xx">
1013   This class of status code indicates a provisional response,
1014   consisting only of the Status-Line and optional headers, and is
1015   terminated by an empty line. There are no required headers for this
1016   class of status code. Since HTTP/1.0 did not define any 1xx status
1017   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1018   except under experimental conditions.
1021   A client &MUST; be prepared to accept one or more 1xx status responses
1022   prior to a regular response, even if the client does not expect a 100
1023   (Continue) status message. Unexpected 1xx status responses &MAY; be
1024   ignored by a user agent.
1027   Proxies &MUST; forward 1xx responses, unless the connection between the
1028   proxy and its client has been closed, or unless the proxy itself
1029   requested the generation of the 1xx response. (For example, if a
1030   proxy adds a "Expect: 100-continue" field when it forwards a request,
1031   then it need not forward the corresponding 100 (Continue)
1032   response(s).)
1035<section title="100 Continue" anchor="status.100">
1036  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1037  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1039   The client &SHOULD; continue with its request. This interim response is
1040   used to inform the client that the initial part of the request has
1041   been received and has not yet been rejected by the server. The client
1042   &SHOULD; continue by sending the remainder of the request or, if the
1043   request has already been completed, ignore this response. The server
1044   &MUST; send a final response after the request has been completed. See
1045   &use100; for detailed discussion of the use and handling of this
1046   status code.
1050<section title="101 Switching Protocols" anchor="status.101">
1051  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1052  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1054   The server understands and is willing to comply with the client's
1055   request, via the Upgrade message header field (&header-upgrade;), for a
1056   change in the application protocol being used on this connection. The
1057   server will switch protocols to those defined by the response's
1058   Upgrade header field immediately after the empty line which
1059   terminates the 101 response.
1062   The protocol &SHOULD; be switched only when it is advantageous to do
1063   so. For example, switching to a newer version of HTTP is advantageous
1064   over older versions, and switching to a real-time, synchronous
1065   protocol might be advantageous when delivering resources that use
1066   such features.
1071<section title="Successful 2xx" anchor="status.2xx">
1073   This class of status code indicates that the client's request was
1074   successfully received, understood, and accepted.
1077<section title="200 OK" anchor="status.200">
1078  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1079  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1081   The request has succeeded. The information returned with the response
1082   is dependent on the method used in the request, for example:
1083  <list style="hanging">
1084    <t hangText="GET">
1085          an entity corresponding to the requested resource is sent in
1086          the response;
1087    </t>
1088    <t hangText="HEAD">
1089          the entity-header fields corresponding to the requested
1090          resource are sent in the response without any message-body;
1091    </t>
1092    <t hangText="POST">
1093      an entity describing or containing the result of the action;
1094    </t>
1095    <t hangText="TRACE">
1096      an entity containing the request message as received by the
1097      end server.
1098    </t>
1099  </list>
1103<section title="201 Created" anchor="status.201">
1104  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1105  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1107   The request has been fulfilled and resulted in a new resource being
1108   created. The newly created resource can be referenced by the URI(s)
1109   returned in the entity of the response, with the most specific URI
1110   for the resource given by a Location header field. The response
1111   &SHOULD; include an entity containing a list of resource
1112   characteristics and location(s) from which the user or user agent can
1113   choose the one most appropriate. The entity format is specified by
1114   the media type given in the Content-Type header field. The origin
1115   server &MUST; create the resource before returning the 201 status code.
1116   If the action cannot be carried out immediately, the server &SHOULD;
1117   respond with 202 (Accepted) response instead.
1120   A 201 response &MAY; contain an ETag response header field indicating
1121   the current value of the entity tag for the requested variant just
1122   created, see &header-etag;.
1126<section title="202 Accepted" anchor="status.202">
1127  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1128  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1130   The request has been accepted for processing, but the processing has
1131   not been completed.  The request might or might not eventually be
1132   acted upon, as it might be disallowed when processing actually takes
1133   place. There is no facility for re-sending a status code from an
1134   asynchronous operation such as this.
1137   The 202 response is intentionally non-committal. Its purpose is to
1138   allow a server to accept a request for some other process (perhaps a
1139   batch-oriented process that is only run once per day) without
1140   requiring that the user agent's connection to the server persist
1141   until the process is completed. The entity returned with this
1142   response &SHOULD; include an indication of the request's current status
1143   and either a pointer to a status monitor or some estimate of when the
1144   user can expect the request to be fulfilled.
1148<section title="203 Non-Authoritative Information" anchor="status.203">
1149  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1150  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1152   The returned metainformation in the entity-header is not the
1153   definitive set as available from the origin server, but is gathered
1154   from a local or a third-party copy. The set presented &MAY; be a subset
1155   or superset of the original version. For example, including local
1156   annotation information about the resource might result in a superset
1157   of the metainformation known by the origin server. Use of this
1158   response code is not required and is only appropriate when the
1159   response would otherwise be 200 (OK).
1163<section title="204 No Content" anchor="status.204">
1164  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1165  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1167   The server has fulfilled the request but does not need to return an
1168   entity-body, and might want to return updated metainformation. The
1169   response &MAY; include new or updated metainformation in the form of
1170   entity-headers, which if present &SHOULD; be associated with the
1171   requested variant.
1174   If the client is a user agent, it &SHOULD-NOT;  change its document view
1175   from that which caused the request to be sent. This response is
1176   primarily intended to allow input for actions to take place without
1177   causing a change to the user agent's active document view, although
1178   any new or updated metainformation &SHOULD; be applied to the document
1179   currently in the user agent's active view.
1182   The 204 response &MUST-NOT; include a message-body, and thus is always
1183   terminated by the first empty line after the header fields.
1187<section title="205 Reset Content" anchor="status.205">
1188  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1189  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1191   The server has fulfilled the request and the user agent &SHOULD; reset
1192   the document view which caused the request to be sent. This response
1193   is primarily intended to allow input for actions to take place via
1194   user input, followed by a clearing of the form in which the input is
1195   given so that the user can easily initiate another input action. The
1196   response &MUST-NOT; include an entity.
1200<section title="206 Partial Content" anchor="status.206">
1201  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1202  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1204   The server has fulfilled the partial GET request for the resource
1205   and the enclosed entity is a partial representation as defined in &range;.
1210<section title="Redirection 3xx" anchor="status.3xx">
1212   This class of status code indicates that further action needs to be
1213   taken by the user agent in order to fulfill the request.  The action
1214   required &MAY; be carried out by the user agent without interaction
1215   with the user if and only if the method used in the second request is
1216   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1217   such loops generate network traffic for each redirection.
1218  <list><t>
1219      <x:h>Note:</x:h> previous versions of this specification recommended a
1220      maximum of five redirections. Content developers should be aware
1221      that there might be clients that implement such a fixed
1222      limitation.
1223  </t></list>
1226<section title="300 Multiple Choices" anchor="status.300">
1227  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1228  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1230   The requested resource corresponds to any one of a set of
1231   representations, each with its own specific location, and agent-driven
1232   negotiation information (&content-negotiation;) is being provided so that
1233   the user (or user agent) can select a preferred representation and
1234   redirect its request to that location.
1237   Unless it was a HEAD request, the response &SHOULD; include an entity
1238   containing a list of resource characteristics and location(s) from
1239   which the user or user agent can choose the one most appropriate. The
1240   entity format is specified by the media type given in the Content-Type
1241   header field. Depending upon the format and the capabilities of
1242   the user agent, selection of the most appropriate choice &MAY; be
1243   performed automatically. However, this specification does not define
1244   any standard for such automatic selection.
1247   If the server has a preferred choice of representation, it &SHOULD;
1248   include the specific URI for that representation in the Location
1249   field; user agents &MAY; use the Location field value for automatic
1250   redirection. This response is cacheable unless indicated otherwise.
1254<section title="301 Moved Permanently" anchor="status.301">
1255  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1256  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1258   The requested resource has been assigned a new permanent URI and any
1259   future references to this resource &SHOULD; use one of the returned
1260   URIs.  Clients with link editing capabilities ought to automatically
1261   re-link references to the Request-URI to one or more of the new
1262   references returned by the server, where possible. This response is
1263   cacheable unless indicated otherwise.
1266   The new permanent URI &SHOULD; be given by the Location field in the
1267   response. Unless the request method was HEAD, the entity of the
1268   response &SHOULD; contain a short hypertext note with a hyperlink to
1269   the new URI(s).
1272   If the 301 status code is received in response to a request method
1273   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1274   then the request &MAY; be automatically redirected by the user agent without
1275   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1276   request unless it can be confirmed by the user, since this might
1277   change the conditions under which the request was issued.
1278  <list><t>
1279      <x:h>Note:</x:h> When automatically redirecting a POST request after
1280      receiving a 301 status code, some existing HTTP/1.0 user agents
1281      will erroneously change it into a GET request.
1282  </t></list>
1286<section title="302 Found" anchor="status.302">
1287  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1288  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1290   The requested resource resides temporarily under a different URI.
1291   Since the redirection might be altered on occasion, the client &SHOULD;
1292   continue to use the Request-URI for future requests.  This response
1293   is only cacheable if indicated by a Cache-Control or Expires header
1294   field.
1297   The temporary URI &SHOULD; be given by the Location field in the
1298   response. Unless the request method was HEAD, the entity of the
1299   response &SHOULD; contain a short hypertext note with a hyperlink to
1300   the new URI(s).
1303   If the 302 status code is received in response to a request method
1304   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1305   then the request &MAY; be automatically redirected by the user agent without
1306   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1307   request unless it can be confirmed by the user, since this might
1308   change the conditions under which the request was issued.
1309  <list><t>
1310      <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1311      to change the method on the redirected request.  However, most
1312      existing user agent implementations treat 302 as if it were a 303
1313      response, performing a GET on the Location field-value regardless
1314      of the original request method. The status codes 303 and 307 have
1315      been added for servers that wish to make unambiguously clear which
1316      kind of reaction is expected of the client.
1317  </t></list>
1321<section title="303 See Other" anchor="status.303">
1322  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1323  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1325   The server directs the user agent to a different resource, indicated
1326   by a URI in the Location header field, that provides an indirect
1327   response to the original request.  The user agent &MAY; perform a GET
1328   request on the URI in the Location field in order to obtain a
1329   representation corresponding to the response, be redirected again,
1330   or end with an error status.  The Location URI is not a substitute
1331   reference for the originally requested resource.
1334   The 303 status is generally applicable to any HTTP method.  It is
1335   primarily used to allow the output of a POST action to redirect
1336   the user agent to a selected resource, since doing so provides the
1337   information corresponding to the POST response in a form that
1338   can be separately identified, bookmarked, and cached independent
1339   of the original request.
1342   A 303 response to a GET request indicates that the requested
1343   resource does not have a representation of its own that can be
1344   transferred by the server over HTTP.  The Location URI indicates a
1345   resource that is descriptive of the requested resource such that
1346   the follow-on representation may be useful without implying that
1347   it adequately represents the previously requested resource.
1348   Note that answers to the questions of what can be represented, what
1349   representations are adequate, and what might be a useful description
1350   are outside the scope of HTTP and thus entirely determined by the
1351   resource owner(s).
1354   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1355   cacheable by Cache-Control or Expires header fields.  Except for
1356   responses to a HEAD request, the entity of a 303 response &SHOULD;
1357   contain a short hypertext note with a hyperlink to the Location URI.
1361<section title="304 Not Modified" anchor="status.304">
1362  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1363  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1365   The response to the request has not been modified since the conditions
1366   indicated by the client's conditional GET request, as defined in &conditional;.
1370<section title="305 Use Proxy" anchor="status.305">
1371  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1372  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1374   The 305 status was defined in a previous version of this specification
1375   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1379<section title="306 (Unused)" anchor="status.306">
1380  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1381  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1383   The 306 status code was used in a previous version of the
1384   specification, is no longer used, and the code is reserved.
1388<section title="307 Temporary Redirect" anchor="status.307">
1389  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1390  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1392   The requested resource resides temporarily under a different URI.
1393   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1394   continue to use the Request-URI for future requests.  This response
1395   is only cacheable if indicated by a Cache-Control or Expires header
1396   field.
1399   The temporary URI &SHOULD; be given by the Location field in the
1400   response. Unless the request method was HEAD, the entity of the
1401   response &SHOULD; contain a short hypertext note with a hyperlink to
1402   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1403   understand the 307 status. Therefore, the note &SHOULD; contain the
1404   information necessary for a user to repeat the original request on
1405   the new URI.
1408   If the 307 status code is received in response to a request method
1409   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1410   then the request &MAY; be automatically redirected by the user agent without
1411   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1412   request unless it can be confirmed by the user, since this might
1413   change the conditions under which the request was issued.
1418<section title="Client Error 4xx" anchor="status.4xx">
1420   The 4xx class of status code is intended for cases in which the
1421   client seems to have erred. Except when responding to a HEAD request,
1422   the server &SHOULD; include an entity containing an explanation of the
1423   error situation, and whether it is a temporary or permanent
1424   condition. These status codes are applicable to any request method.
1425   User agents &SHOULD; display any included entity to the user.
1428   If the client is sending data, a server implementation using TCP
1429   &SHOULD; be careful to ensure that the client acknowledges receipt of
1430   the packet(s) containing the response, before the server closes the
1431   input connection. If the client continues sending data to the server
1432   after the close, the server's TCP stack will send a reset packet to
1433   the client, which may erase the client's unacknowledged input buffers
1434   before they can be read and interpreted by the HTTP application.
1437<section title="400 Bad Request" anchor="status.400">
1438  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1439  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1441   The request could not be understood by the server due to malformed
1442   syntax. The client &SHOULD-NOT;  repeat the request without
1443   modifications.
1447<section title="401 Unauthorized" anchor="status.401">
1448  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1449  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1451   The request requires user authentication (see &auth;).
1455<section title="402 Payment Required" anchor="status.402">
1456  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1457  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1459   This code is reserved for future use.
1463<section title="403 Forbidden" anchor="status.403">
1464  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1465  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1467   The server understood the request, but is refusing to fulfill it.
1468   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1469   If the request method was not HEAD and the server wishes to make
1470   public why the request has not been fulfilled, it &SHOULD; describe the
1471   reason for the refusal in the entity.  If the server does not wish to
1472   make this information available to the client, the status code 404
1473   (Not Found) can be used instead.
1477<section title="404 Not Found" anchor="status.404">
1478  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1479  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1481   The server has not found anything matching the Request-URI. No
1482   indication is given of whether the condition is temporary or
1483   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1484   knows, through some internally configurable mechanism, that an old
1485   resource is permanently unavailable and has no forwarding address.
1486   This status code is commonly used when the server does not wish to
1487   reveal exactly why the request has been refused, or when no other
1488   response is applicable.
1492<section title="405 Method Not Allowed" anchor="status.405">
1493  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1494  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1496   The method specified in the Request-Line is not allowed for the
1497   resource identified by the Request-URI. The response &MUST; include an
1498   Allow header containing a list of valid methods for the requested
1499   resource.
1503<section title="406 Not Acceptable" anchor="status.406">
1504  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1505  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1507   The resource identified by the request is only capable of generating
1508   response entities which have content characteristics not acceptable
1509   according to the accept headers sent in the request.
1512   Unless it was a HEAD request, the response &SHOULD; include an entity
1513   containing a list of available entity characteristics and location(s)
1514   from which the user or user agent can choose the one most
1515   appropriate. The entity format is specified by the media type given
1516   in the Content-Type header field. Depending upon the format and the
1517   capabilities of the user agent, selection of the most appropriate
1518   choice &MAY; be performed automatically. However, this specification
1519   does not define any standard for such automatic selection.
1520  <list><t>
1521      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1522      not acceptable according to the accept headers sent in the
1523      request. In some cases, this may even be preferable to sending a
1524      406 response. User agents are encouraged to inspect the headers of
1525      an incoming response to determine if it is acceptable.
1526  </t></list>
1529   If the response could be unacceptable, a user agent &SHOULD;
1530   temporarily stop receipt of more data and query the user for a
1531   decision on further actions.
1535<section title="407 Proxy Authentication Required" anchor="status.407">
1536  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1537  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1539   This code is similar to 401 (Unauthorized), but indicates that the
1540   client must first authenticate itself with the proxy (see &auth;).
1544<section title="408 Request Timeout" anchor="status.408">
1545  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1546  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1548   The client did not produce a request within the time that the server
1549   was prepared to wait. The client &MAY; repeat the request without
1550   modifications at any later time.
1554<section title="409 Conflict" anchor="status.409">
1555  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1556  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1558   The request could not be completed due to a conflict with the current
1559   state of the resource. This code is only allowed in situations where
1560   it is expected that the user might be able to resolve the conflict
1561   and resubmit the request. The response body &SHOULD; include enough
1562   information for the user to recognize the source of the conflict.
1563   Ideally, the response entity would include enough information for the
1564   user or user agent to fix the problem; however, that might not be
1565   possible and is not required.
1568   Conflicts are most likely to occur in response to a PUT request. For
1569   example, if versioning were being used and the entity being PUT
1570   included changes to a resource which conflict with those made by an
1571   earlier (third-party) request, the server might use the 409 response
1572   to indicate that it can't complete the request. In this case, the
1573   response entity would likely contain a list of the differences
1574   between the two versions in a format defined by the response
1575   Content-Type.
1579<section title="410 Gone" anchor="status.410">
1580  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1581  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1583   The requested resource is no longer available at the server and no
1584   forwarding address is known. This condition is expected to be
1585   considered permanent. Clients with link editing capabilities &SHOULD;
1586   delete references to the Request-URI after user approval. If the
1587   server does not know, or has no facility to determine, whether or not
1588   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1589   used instead. This response is cacheable unless indicated otherwise.
1592   The 410 response is primarily intended to assist the task of web
1593   maintenance by notifying the recipient that the resource is
1594   intentionally unavailable and that the server owners desire that
1595   remote links to that resource be removed. Such an event is common for
1596   limited-time, promotional services and for resources belonging to
1597   individuals no longer working at the server's site. It is not
1598   necessary to mark all permanently unavailable resources as "gone" or
1599   to keep the mark for any length of time -- that is left to the
1600   discretion of the server owner.
1604<section title="411 Length Required" anchor="status.411">
1605  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1606  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1608   The server refuses to accept the request without a defined Content-Length.
1609   The client &MAY; repeat the request if it adds a valid
1610   Content-Length header field containing the length of the message-body
1611   in the request message.
1615<section title="412 Precondition Failed" anchor="status.412">
1616  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1617  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1619   The precondition given in one or more of the request-header fields
1620   evaluated to false when it was tested on the server, as defined in
1621   &conditional;.
1625<section title="413 Request Entity Too Large" anchor="status.413">
1626  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1627  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1629   The server is refusing to process a request because the request
1630   entity is larger than the server is willing or able to process. The
1631   server &MAY; close the connection to prevent the client from continuing
1632   the request.
1635   If the condition is temporary, the server &SHOULD; include a Retry-After
1636   header field to indicate that it is temporary and after what
1637   time the client &MAY; try again.
1641<section title="414 Request-URI Too Long" anchor="status.414">
1642  <iref primary="true" item="414 Request-URI Too Long (status code)" x:for-anchor=""/>
1643  <iref primary="true" item="Status Codes" subitem="414 Request-URI Too Long" x:for-anchor=""/>
1645   The server is refusing to service the request because the Request-URI
1646   is longer than the server is willing to interpret. This rare
1647   condition is only likely to occur when a client has improperly
1648   converted a POST request to a GET request with long query
1649   information, when the client has descended into a URI "black hole" of
1650   redirection (e.g., a redirected URI prefix that points to a suffix of
1651   itself), or when the server is under attack by a client attempting to
1652   exploit security holes present in some servers using fixed-length
1653   buffers for reading or manipulating the Request-URI.
1657<section title="415 Unsupported Media Type" anchor="status.415">
1658  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1659  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1661   The server is refusing to service the request because the entity of
1662   the request is in a format not supported by the requested resource
1663   for the requested method.
1667<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1668  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1669  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1671   The request included a Range request-header field (&header-range;) and none of
1672   the range-specifier values in this field overlap the current extent
1673   of the selected resource.
1677<section title="417 Expectation Failed" anchor="status.417">
1678  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1679  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1681   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1682   could not be met by this server, or, if the server is a proxy,
1683   the server has unambiguous evidence that the request could not be met
1684   by the next-hop server.
1689<section title="Server Error 5xx" anchor="status.5xx">
1691   Response status codes beginning with the digit "5" indicate cases in
1692   which the server is aware that it has erred or is incapable of
1693   performing the request. Except when responding to a HEAD request, the
1694   server &SHOULD; include an entity containing an explanation of the
1695   error situation, and whether it is a temporary or permanent
1696   condition. User agents &SHOULD; display any included entity to the
1697   user. These response codes are applicable to any request method.
1700<section title="500 Internal Server Error" anchor="status.500">
1701  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1702  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1704   The server encountered an unexpected condition which prevented it
1705   from fulfilling the request.
1709<section title="501 Not Implemented" anchor="status.501">
1710  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1711  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1713   The server does not support the functionality required to fulfill the
1714   request. This is the appropriate response when the server does not
1715   recognize the request method and is not capable of supporting it for
1716   any resource.
1720<section title="502 Bad Gateway" anchor="status.502">
1721  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1722  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1724   The server, while acting as a gateway or proxy, received an invalid
1725   response from the upstream server it accessed in attempting to
1726   fulfill the request.
1730<section title="503 Service Unavailable" anchor="status.503">
1731  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1732  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1734   The server is currently unable to handle the request due to a
1735   temporary overloading or maintenance of the server. The implication
1736   is that this is a temporary condition which will be alleviated after
1737   some delay. If known, the length of the delay &MAY; be indicated in a
1738   Retry-After header. If no Retry-After is given, the client &SHOULD;
1739   handle the response as it would for a 500 response.
1740  <list><t>
1741      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1742      server must use it when becoming overloaded. Some servers may wish
1743      to simply refuse the connection.
1744  </t></list>
1748<section title="504 Gateway Timeout" anchor="status.504">
1749  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1750  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1752   The server, while acting as a gateway or proxy, did not receive a
1753   timely response from the upstream server specified by the URI (e.g.
1754   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1755   to access in attempting to complete the request.
1756  <list><t>
1757      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1758      return 400 or 500 when DNS lookups time out.
1759  </t></list>
1763<section title="505 HTTP Version Not Supported" anchor="status.505">
1764  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1765  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1767   The server does not support, or refuses to support, the protocol
1768   version that was used in the request message. The server is
1769   indicating that it is unable or unwilling to complete the request
1770   using the same major version as the client, as described in &http-version;,
1771   other than with this error message. The response &SHOULD; contain
1772   an entity describing why that version is not supported and what other
1773   protocols are supported by that server.
1781<section title="Header Field Definitions" anchor="header.fields">
1783   This section defines the syntax and semantics of HTTP/1.1 header fields
1784   related to request and response semantics.
1787   For entity-header fields, both sender and recipient refer to either the
1788   client or the server, depending on who sends and who receives the entity.
1791<section title="Allow" anchor="header.allow">
1792  <iref primary="true" item="Allow header" x:for-anchor=""/>
1793  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1794  <x:anchor-alias value="Allow"/>
1796      The Allow response-header field lists the set of methods advertised as
1797      supported by the resource identified by the Request-URI. The purpose of
1798      this field is strictly to inform the recipient of valid methods
1799      associated with the resource. An Allow header field &MUST; be
1800      present in a 405 (Method Not Allowed) response.
1802<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/>
1803  <x:ref>Allow</x:ref>   = "Allow" ":" #<x:ref>Method</x:ref>
1806      Example of use:
1808<figure><artwork type="example">
1809       Allow: GET, HEAD, PUT
1812      The actual set of allowed methods is defined
1813      by the origin server at the time of each request.
1816      A proxy &MUST-NOT; modify the Allow header field even if it does not
1817      understand all the methods specified, since the user agent might
1818      have other means of communicating with the origin server.
1822<section title="Expect" anchor="header.expect">
1823  <iref primary="true" item="Expect header" x:for-anchor=""/>
1824  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1825  <x:anchor-alias value="Expect"/>
1826  <x:anchor-alias value="expectation"/>
1827  <x:anchor-alias value="expectation-extension"/>
1828  <x:anchor-alias value="expect-params"/>
1830   The Expect request-header field is used to indicate that particular
1831   server behaviors are required by the client.
1833<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
1834  <x:ref>Expect</x:ref>       =  "Expect" ":" 1#<x:ref>expectation</x:ref>
1836  <x:ref>expectation</x:ref>  =  "100-continue" / <x:ref>expectation-extension</x:ref>
1837  <x:ref>expectation-extension</x:ref> =  <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1838                           *<x:ref>expect-params</x:ref> ]
1839  <x:ref>expect-params</x:ref> =  ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1842   A server that does not understand or is unable to comply with any of
1843   the expectation values in the Expect field of a request &MUST; respond
1844   with appropriate error status. The server &MUST; respond with a 417
1845   (Expectation Failed) status if any of the expectations cannot be met
1846   or, if there are other problems with the request, some other 4xx
1847   status.
1850   This header field is defined with extensible syntax to allow for
1851   future extensions. If a server receives a request containing an
1852   Expect field that includes an expectation-extension that it does not
1853   support, it &MUST; respond with a 417 (Expectation Failed) status.
1856   Comparison of expectation values is case-insensitive for unquoted
1857   tokens (including the 100-continue token), and is case-sensitive for
1858   quoted-string expectation-extensions.
1861   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1862   return a 417 (Expectation Failed) status if it receives a request
1863   with an expectation that it cannot meet. However, the Expect
1864   request-header itself is end-to-end; it &MUST; be forwarded if the
1865   request is forwarded.
1868   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1869   Expect header.
1872   See &use100; for the use of the 100 (Continue) status.
1876<section title="From" anchor="header.from">
1877  <iref primary="true" item="From header" x:for-anchor=""/>
1878  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1879  <x:anchor-alias value="From"/>
1880  <x:anchor-alias value="mailbox"/>
1882   The From request-header field, if given, &SHOULD; contain an Internet
1883   e-mail address for the human user who controls the requesting user
1884   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1885   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
1887<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/>
1888  <x:ref>From</x:ref>    = "From" ":" <x:ref>mailbox</x:ref>
1890  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
1893   An example is:
1895<figure><artwork type="example">
1896    From:
1899   This header field &MAY; be used for logging purposes and as a means for
1900   identifying the source of invalid or unwanted requests. It &SHOULD-NOT;
1901   be used as an insecure form of access protection. The interpretation
1902   of this field is that the request is being performed on behalf of the
1903   person given, who accepts responsibility for the method performed. In
1904   particular, robot agents &SHOULD; include this header so that the
1905   person responsible for running the robot can be contacted if problems
1906   occur on the receiving end.
1909   The Internet e-mail address in this field &MAY; be separate from the
1910   Internet host which issued the request. For example, when a request
1911   is passed through a proxy the original issuer's address &SHOULD; be
1912   used.
1915   The client &SHOULD-NOT;  send the From header field without the user's
1916   approval, as it might conflict with the user's privacy interests or
1917   their site's security policy. It is strongly recommended that the
1918   user be able to disable, enable, and modify the value of this field
1919   at any time prior to a request.
1923<section title="Location" anchor="header.location">
1924  <iref primary="true" item="Location header" x:for-anchor=""/>
1925  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1926  <x:anchor-alias value="Location"/>
1928   The Location response-header field is used for the identification of a
1929   new resource or to redirect the recipient to a location other than the
1930   Request-URI for completion of the request.  For 201 (Created)
1931   responses, the Location is that of the new resource which was created
1932   by the request. For 3xx responses, the location &SHOULD; indicate the
1933   server's preferred URI for automatic redirection to the resource. The
1934   field value consists of a single absolute URI.
1936<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/>
1937  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>absoluteURI</x:ref> [ "#" <x:ref>fragment</x:ref> ]
1940   An example is:
1942<figure><artwork type="example">
1943    Location:
1946  <list><t>
1947      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1948      from Location in that the Content-Location identifies the original
1949      location of the entity enclosed in the response. It is therefore
1950      possible for a response to contain header fields for both Location
1951      and Content-Location.
1952  </t></list>
1955   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1956   <list style="symbols">
1957      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1958      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1959      <t>With 305 Use Proxy.</t>
1960   </list>
1964<section title="Max-Forwards" anchor="header.max-forwards">
1965  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1966  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1967  <x:anchor-alias value="Max-Forwards"/>
1969   The Max-Forwards request-header field provides a mechanism with the
1970   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
1971   number of proxies or gateways that can forward the request to the
1972   next inbound server. This can be useful when the client is attempting
1973   to trace a request chain which appears to be failing or looping in
1974   mid-chain.
1976<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/>
1977  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" 1*<x:ref>DIGIT</x:ref>
1980   The Max-Forwards value is a decimal integer indicating the remaining
1981   number of times this request message may be forwarded.
1984   Each proxy or gateway recipient of a TRACE or OPTIONS request
1985   containing a Max-Forwards header field &MUST; check and update its
1986   value prior to forwarding the request. If the received value is zero
1987   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
1988   respond as the final recipient. If the received Max-Forwards value is
1989   greater than zero, then the forwarded message &MUST; contain an updated
1990   Max-Forwards field with a value decremented by one (1).
1993   The Max-Forwards header field &MAY; be ignored for all other methods
1994   defined by this specification and for any extension methods for which
1995   it is not explicitly referred to as part of that method definition.
1999<section title="Referer" anchor="header.referer">
2000  <iref primary="true" item="Referer header" x:for-anchor=""/>
2001  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2002  <x:anchor-alias value="Referer"/>
2004   The Referer[sic] request-header field allows the client to specify,
2005   for the server's benefit, the address (URI) of the resource from
2006   which the Request-URI was obtained (the "referrer", although the
2007   header field is misspelled.) The Referer request-header allows a
2008   server to generate lists of back-links to resources for interest,
2009   logging, optimized caching, etc. It also allows obsolete or mistyped
2010   links to be traced for maintenance. The Referer field &MUST-NOT; be
2011   sent if the Request-URI was obtained from a source that does not have
2012   its own URI, such as input from the user keyboard.
2014<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/>
2015  <x:ref>Referer</x:ref>        = "Referer" ":" ( <x:ref>absoluteURI</x:ref> / <x:ref>relativeURI</x:ref> )
2018   Example:
2020<figure><artwork type="example">
2021    Referer:
2024   If the field value is a relative URI, it &SHOULD; be interpreted
2025   relative to the Request-URI. The URI &MUST-NOT; include a fragment. See
2026   <xref target=""/> for security considerations.
2030<section title="Retry-After" anchor="header.retry-after">
2031  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2032  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2033  <x:anchor-alias value="Retry-After"/>
2035   The Retry-After response-header field can be used with a 503 (Service
2036   Unavailable) response to indicate how long the service is expected to
2037   be unavailable to the requesting client. This field &MAY; also be used
2038   with any 3xx (Redirection) response to indicate the minimum time the
2039   user-agent is asked wait before issuing the redirected request. The
2040   value of this field can be either an HTTP-date or an integer number
2041   of seconds (in decimal) after the time of the response.
2043<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/>
2044  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" ( <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref> )
2046<t anchor="">
2047  <x:anchor-alias value="delta-seconds"/>
2048   Time spans are non-negative decimal integers, representing time in
2049   seconds.
2051<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2052  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2055   Two examples of its use are
2057<figure><artwork type="example">
2058    Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2059    Retry-After: 120
2062   In the latter example, the delay is 2 minutes.
2066<section title="Server" anchor="header.server">
2067  <iref primary="true" item="Server header" x:for-anchor=""/>
2068  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2069  <x:anchor-alias value="Server"/>
2071   The Server response-header field contains information about the
2072   software used by the origin server to handle the request. The field
2073   can contain multiple product tokens (&product-tokens;) and comments
2074   identifying the server and any significant subproducts. The product
2075   tokens are listed in order of their significance for identifying the
2076   application.
2078<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/>
2079  <x:ref>Server</x:ref>         = "Server" ":" 1*( <x:ref>product</x:ref> / <x:ref>comment</x:ref> )
2082   Example:
2084<figure><artwork type="example">
2085    Server: CERN/3.0 libwww/2.17
2088   If the response is being forwarded through a proxy, the proxy
2089   application &MUST-NOT; modify the Server response-header. Instead, it
2090   &MUST; include a Via field (as described in &header-via;).
2091  <list><t>
2092      <x:h>Note:</x:h> Revealing the specific software version of the server might
2093      allow the server machine to become more vulnerable to attacks
2094      against software that is known to contain security holes. Server
2095      implementors are encouraged to make this field a configurable
2096      option.
2097  </t></list>
2101<section title="User-Agent" anchor="header.user-agent">
2102  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2103  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2104  <x:anchor-alias value="User-Agent"/>
2106   The User-Agent request-header field contains information about the
2107   user agent originating the request. This is for statistical purposes,
2108   the tracing of protocol violations, and automated recognition of user
2109   agents for the sake of tailoring responses to avoid particular user
2110   agent limitations. User agents &SHOULD; include this field with
2111   requests. The field can contain multiple product tokens (&product-tokens;)
2112   and comments identifying the agent and any subproducts which form a
2113   significant part of the user agent. By convention, the product tokens
2114   are listed in order of their significance for identifying the
2115   application.
2117<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/>
2118  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" 1*( <x:ref>product</x:ref> / <x:ref>comment</x:ref> )
2121   Example:
2123<figure><artwork type="example">
2124    User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2130<section title="IANA Considerations" anchor="IANA.considerations">
2132<section title="Method Registry" anchor="method.registration">
2134  The registration procedure for HTTP Methods is defined by
2135  <xref target="method.registry"/> of this document.
2138   The HTTP Method Registry located at <eref target=""/>
2139   should be populated with the registrations below:
2141<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2142<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2143   <ttcol>Method</ttcol>
2144   <ttcol>Safe</ttcol>
2145   <ttcol>Reference</ttcol>
2146   <c>CONNECT</c>
2147   <c>no</c>
2148   <c>
2149      <xref target="CONNECT"/>
2150   </c>
2151   <c>DELETE</c>
2152   <c>no</c>
2153   <c>
2154      <xref target="DELETE"/>
2155   </c>
2156   <c>GET</c>
2157   <c>yes</c>
2158   <c>
2159      <xref target="GET"/>
2160   </c>
2161   <c>HEAD</c>
2162   <c>yes</c>
2163   <c>
2164      <xref target="HEAD"/>
2165   </c>
2166   <c>OPTIONS</c>
2167   <c>yes</c>
2168   <c>
2169      <xref target="OPTIONS"/>
2170   </c>
2171   <c>POST</c>
2172   <c>no</c>
2173   <c>
2174      <xref target="POST"/>
2175   </c>
2176   <c>PUT</c>
2177   <c>no</c>
2178   <c>
2179      <xref target="PUT"/>
2180   </c>
2181   <c>TRACE</c>
2182   <c>yes</c>
2183   <c>
2184      <xref target="TRACE"/>
2185   </c>
2190<section title="Status Code Registry" anchor="status.code.registration">
2192   The registration procedure for HTTP Status Codes -- previously defined
2193   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2194   by <xref target="status.code.registry"/> of this document.
2197   The HTTP Status Code Registry located at <eref target=""/>
2198   should be updated with the registrations below:
2200<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2201<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2202   <ttcol>Value</ttcol>
2203   <ttcol>Description</ttcol>
2204   <ttcol>Reference</ttcol>
2205   <c>100</c>
2206   <c>Continue</c>
2207   <c>
2208      <xref target="status.100"/>
2209   </c>
2210   <c>101</c>
2211   <c>Switching Protocols</c>
2212   <c>
2213      <xref target="status.101"/>
2214   </c>
2215   <c>200</c>
2216   <c>OK</c>
2217   <c>
2218      <xref target="status.200"/>
2219   </c>
2220   <c>201</c>
2221   <c>Created</c>
2222   <c>
2223      <xref target="status.201"/>
2224   </c>
2225   <c>202</c>
2226   <c>Accepted</c>
2227   <c>
2228      <xref target="status.202"/>
2229   </c>
2230   <c>203</c>
2231   <c>Non-Authoritative Information</c>
2232   <c>
2233      <xref target="status.203"/>
2234   </c>
2235   <c>204</c>
2236   <c>No Content</c>
2237   <c>
2238      <xref target="status.204"/>
2239   </c>
2240   <c>205</c>
2241   <c>Reset Content</c>
2242   <c>
2243      <xref target="status.205"/>
2244   </c>
2245   <c>206</c>
2246   <c>Partial Content</c>
2247   <c>
2248      <xref target="status.206"/>
2249   </c>
2250   <c>300</c>
2251   <c>Multiple Choices</c>
2252   <c>
2253      <xref target="status.300"/>
2254   </c>
2255   <c>301</c>
2256   <c>Moved Permanently</c>
2257   <c>
2258      <xref target="status.301"/>
2259   </c>
2260   <c>302</c>
2261   <c>Found</c>
2262   <c>
2263      <xref target="status.302"/>
2264   </c>
2265   <c>303</c>
2266   <c>See Other</c>
2267   <c>
2268      <xref target="status.303"/>
2269   </c>
2270   <c>304</c>
2271   <c>Not Modified</c>
2272   <c>
2273      <xref target="status.304"/>
2274   </c>
2275   <c>305</c>
2276   <c>Use Proxy</c>
2277   <c>
2278      <xref target="status.305"/>
2279   </c>
2280   <c>306</c>
2281   <c>(Unused)</c>
2282   <c>
2283      <xref target="status.306"/>
2284   </c>
2285   <c>307</c>
2286   <c>Temporary Redirect</c>
2287   <c>
2288      <xref target="status.307"/>
2289   </c>
2290   <c>400</c>
2291   <c>Bad Request</c>
2292   <c>
2293      <xref target="status.400"/>
2294   </c>
2295   <c>401</c>
2296   <c>Unauthorized</c>
2297   <c>
2298      <xref target="status.401"/>
2299   </c>
2300   <c>402</c>
2301   <c>Payment Required</c>
2302   <c>
2303      <xref target="status.402"/>
2304   </c>
2305   <c>403</c>
2306   <c>Forbidden</c>
2307   <c>
2308      <xref target="status.403"/>
2309   </c>
2310   <c>404</c>
2311   <c>Not Found</c>
2312   <c>
2313      <xref target="status.404"/>
2314   </c>
2315   <c>405</c>
2316   <c>Method Not Allowed</c>
2317   <c>
2318      <xref target="status.405"/>
2319   </c>
2320   <c>406</c>
2321   <c>Not Acceptable</c>
2322   <c>
2323      <xref target="status.406"/>
2324   </c>
2325   <c>407</c>
2326   <c>Proxy Authentication Required</c>
2327   <c>
2328      <xref target="status.407"/>
2329   </c>
2330   <c>408</c>
2331   <c>Request Timeout</c>
2332   <c>
2333      <xref target="status.408"/>
2334   </c>
2335   <c>409</c>
2336   <c>Conflict</c>
2337   <c>
2338      <xref target="status.409"/>
2339   </c>
2340   <c>410</c>
2341   <c>Gone</c>
2342   <c>
2343      <xref target="status.410"/>
2344   </c>
2345   <c>411</c>
2346   <c>Length Required</c>
2347   <c>
2348      <xref target="status.411"/>
2349   </c>
2350   <c>412</c>
2351   <c>Precondition Failed</c>
2352   <c>
2353      <xref target="status.412"/>
2354   </c>
2355   <c>413</c>
2356   <c>Request Entity Too Large</c>
2357   <c>
2358      <xref target="status.413"/>
2359   </c>
2360   <c>414</c>
2361   <c>Request-URI Too Long</c>
2362   <c>
2363      <xref target="status.414"/>
2364   </c>
2365   <c>415</c>
2366   <c>Unsupported Media Type</c>
2367   <c>
2368      <xref target="status.415"/>
2369   </c>
2370   <c>416</c>
2371   <c>Requested Range Not Satisfiable</c>
2372   <c>
2373      <xref target="status.416"/>
2374   </c>
2375   <c>417</c>
2376   <c>Expectation Failed</c>
2377   <c>
2378      <xref target="status.417"/>
2379   </c>
2380   <c>500</c>
2381   <c>Internal Server Error</c>
2382   <c>
2383      <xref target="status.500"/>
2384   </c>
2385   <c>501</c>
2386   <c>Not Implemented</c>
2387   <c>
2388      <xref target="status.501"/>
2389   </c>
2390   <c>502</c>
2391   <c>Bad Gateway</c>
2392   <c>
2393      <xref target="status.502"/>
2394   </c>
2395   <c>503</c>
2396   <c>Service Unavailable</c>
2397   <c>
2398      <xref target="status.503"/>
2399   </c>
2400   <c>504</c>
2401   <c>Gateway Timeout</c>
2402   <c>
2403      <xref target="status.504"/>
2404   </c>
2405   <c>505</c>
2406   <c>HTTP Version Not Supported</c>
2407   <c>
2408      <xref target="status.505"/>
2409   </c>
2413<section title="Message Header Registration" anchor="message.header.registration">
2415   The Message Header Registry located at <eref target=""/> should be updated
2416   with the permanent registrations below (see <xref target="RFC3864"/>):
2418<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2419<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2420   <ttcol>Header Field Name</ttcol>
2421   <ttcol>Protocol</ttcol>
2422   <ttcol>Status</ttcol>
2423   <ttcol>Reference</ttcol>
2424   <c>Allow</c>
2425   <c>http</c>
2426   <c>standard</c>
2427   <c>
2428      <xref target="header.allow"/>
2429   </c>
2430   <c>Expect</c>
2431   <c>http</c>
2432   <c>standard</c>
2433   <c>
2434      <xref target="header.expect"/>
2435   </c>
2436   <c>From</c>
2437   <c>http</c>
2438   <c>standard</c>
2439   <c>
2440      <xref target="header.from"/>
2441   </c>
2442   <c>Location</c>
2443   <c>http</c>
2444   <c>standard</c>
2445   <c>
2446      <xref target="header.location"/>
2447   </c>
2448   <c>Max-Forwards</c>
2449   <c>http</c>
2450   <c>standard</c>
2451   <c>
2452      <xref target="header.max-forwards"/>
2453   </c>
2454   <c>Referer</c>
2455   <c>http</c>
2456   <c>standard</c>
2457   <c>
2458      <xref target="header.referer"/>
2459   </c>
2460   <c>Retry-After</c>
2461   <c>http</c>
2462   <c>standard</c>
2463   <c>
2464      <xref target="header.retry-after"/>
2465   </c>
2466   <c>Server</c>
2467   <c>http</c>
2468   <c>standard</c>
2469   <c>
2470      <xref target="header.server"/>
2471   </c>
2472   <c>User-Agent</c>
2473   <c>http</c>
2474   <c>standard</c>
2475   <c>
2476      <xref target="header.user-agent"/>
2477   </c>
2481   The change controller is: "IETF ( - Internet Engineering Task Force".
2486<section title="Security Considerations" anchor="security.considerations">
2488   This section is meant to inform application developers, information
2489   providers, and users of the security limitations in HTTP/1.1 as
2490   described by this document. The discussion does not include
2491   definitive solutions to the problems revealed, though it does make
2492   some suggestions for reducing security risks.
2495<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2497   Like any generic data transfer protocol, HTTP cannot regulate the
2498   content of the data that is transferred, nor is there any a priori
2499   method of determining the sensitivity of any particular piece of
2500   information within the context of any given request. Therefore,
2501   applications &SHOULD; supply as much control over this information as
2502   possible to the provider of that information. Four header fields are
2503   worth special mention in this context: Server, Via, Referer and From.
2506   Revealing the specific software version of the server might allow the
2507   server machine to become more vulnerable to attacks against software
2508   that is known to contain security holes. Implementors &SHOULD; make the
2509   Server header field a configurable option.
2512   Proxies which serve as a portal through a network firewall &SHOULD;
2513   take special precautions regarding the transfer of header information
2514   that identifies the hosts behind the firewall. In particular, they
2515   &SHOULD; remove, or replace with sanitized versions, any Via fields
2516   generated behind the firewall.
2519   The Referer header allows reading patterns to be studied and reverse
2520   links drawn. Although it can be very useful, its power can be abused
2521   if user details are not separated from the information contained in
2522   the Referer. Even when the personal information has been removed, the
2523   Referer header might indicate a private document's URI whose
2524   publication would be inappropriate.
2527   The information sent in the From field might conflict with the user's
2528   privacy interests or their site's security policy, and hence it
2529   &SHOULD-NOT;  be transmitted without the user being able to disable,
2530   enable, and modify the contents of the field. The user &MUST; be able
2531   to set the contents of this field within a user preference or
2532   application defaults configuration.
2535   We suggest, though do not require, that a convenient toggle interface
2536   be provided for the user to enable or disable the sending of From and
2537   Referer information.
2540   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2541   fields can sometimes be used to determine that a specific client or
2542   server have a particular security hole which might be exploited.
2543   Unfortunately, this same information is often used for other valuable
2544   purposes for which HTTP currently has no better mechanism.
2548<section title="Encoding Sensitive Information in URIs" anchor="">
2550   Because the source of a link might be private information or might
2551   reveal an otherwise private information source, it is strongly
2552   recommended that the user be able to select whether or not the
2553   Referer field is sent. For example, a browser client could have a
2554   toggle switch for browsing openly/anonymously, which would
2555   respectively enable/disable the sending of Referer and From
2556   information.
2559   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2560   HTTP request if the referring page was transferred with a secure
2561   protocol.
2564   Authors of services should not use
2565   GET-based forms for the submission of sensitive data because that
2566   data will be encoded in the Request-URI. Many existing
2567   servers, proxies, and user agents log or display the Request-URI in
2568   places where it might be visible to third parties. Such services can
2569   use POST-based form submission instead.
2573<section title="Location Headers and Spoofing" anchor="location.spoofing">
2575   If a single server supports multiple organizations that do not trust
2576   one another, then it &MUST; check the values of Location and Content-Location
2577   headers in responses that are generated under control of
2578   said organizations to make sure that they do not attempt to
2579   invalidate resources over which they have no authority.
2585<section title="Acknowledgments" anchor="ack">
2590<references title="Normative References">
2592<reference anchor="Part1">
2593  <front>
2594    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2595    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2596      <organization abbrev="Day Software">Day Software</organization>
2597      <address><email></email></address>
2598    </author>
2599    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2600      <organization>One Laptop per Child</organization>
2601      <address><email></email></address>
2602    </author>
2603    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2604      <organization abbrev="HP">Hewlett-Packard Company</organization>
2605      <address><email></email></address>
2606    </author>
2607    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2608      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2609      <address><email></email></address>
2610    </author>
2611    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2612      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2613      <address><email></email></address>
2614    </author>
2615    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2616      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2617      <address><email></email></address>
2618    </author>
2619    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2620      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2621      <address><email></email></address>
2622    </author>
2623    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2624      <organization abbrev="W3C">World Wide Web Consortium</organization>
2625      <address><email></email></address>
2626    </author>
2627    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2628      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2629      <address><email></email></address>
2630    </author>
2631    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2632  </front>
2633  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2634  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2637<reference anchor="Part3">
2638  <front>
2639    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2640    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2641      <organization abbrev="Day Software">Day Software</organization>
2642      <address><email></email></address>
2643    </author>
2644    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2645      <organization>One Laptop per Child</organization>
2646      <address><email></email></address>
2647    </author>
2648    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2649      <organization abbrev="HP">Hewlett-Packard Company</organization>
2650      <address><email></email></address>
2651    </author>
2652    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2653      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2654      <address><email></email></address>
2655    </author>
2656    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2657      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2658      <address><email></email></address>
2659    </author>
2660    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2661      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2662      <address><email></email></address>
2663    </author>
2664    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2665      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2666      <address><email></email></address>
2667    </author>
2668    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2669      <organization abbrev="W3C">World Wide Web Consortium</organization>
2670      <address><email></email></address>
2671    </author>
2672    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2673      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2674      <address><email></email></address>
2675    </author>
2676    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2677  </front>
2678  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2679  <x:source href="p3-payload.xml" basename="p3-payload"/>
2682<reference anchor="Part4">
2683  <front>
2684    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2685    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2686      <organization abbrev="Day Software">Day Software</organization>
2687      <address><email></email></address>
2688    </author>
2689    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2690      <organization>One Laptop per Child</organization>
2691      <address><email></email></address>
2692    </author>
2693    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2694      <organization abbrev="HP">Hewlett-Packard Company</organization>
2695      <address><email></email></address>
2696    </author>
2697    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2698      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2699      <address><email></email></address>
2700    </author>
2701    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2702      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2703      <address><email></email></address>
2704    </author>
2705    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2706      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2707      <address><email></email></address>
2708    </author>
2709    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2710      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2711      <address><email></email></address>
2712    </author>
2713    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2714      <organization abbrev="W3C">World Wide Web Consortium</organization>
2715      <address><email></email></address>
2716    </author>
2717    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2718      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2719      <address><email></email></address>
2720    </author>
2721    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2722  </front>
2723  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2724  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2727<reference anchor="Part5">
2728  <front>
2729    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2730    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2731      <organization abbrev="Day Software">Day Software</organization>
2732      <address><email></email></address>
2733    </author>
2734    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2735      <organization>One Laptop per Child</organization>
2736      <address><email></email></address>
2737    </author>
2738    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2739      <organization abbrev="HP">Hewlett-Packard Company</organization>
2740      <address><email></email></address>
2741    </author>
2742    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2743      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2744      <address><email></email></address>
2745    </author>
2746    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2747      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2748      <address><email></email></address>
2749    </author>
2750    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2751      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2752      <address><email></email></address>
2753    </author>
2754    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2755      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2756      <address><email></email></address>
2757    </author>
2758    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2759      <organization abbrev="W3C">World Wide Web Consortium</organization>
2760      <address><email></email></address>
2761    </author>
2762    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2763      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2764      <address><email></email></address>
2765    </author>
2766    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2767  </front>
2768  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2769  <x:source href="p5-range.xml" basename="p5-range"/>
2772<reference anchor="Part6">
2773  <front>
2774    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2775    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2776      <organization abbrev="Day Software">Day Software</organization>
2777      <address><email></email></address>
2778    </author>
2779    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2780      <organization>One Laptop per Child</organization>
2781      <address><email></email></address>
2782    </author>
2783    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2784      <organization abbrev="HP">Hewlett-Packard Company</organization>
2785      <address><email></email></address>
2786    </author>
2787    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2788      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2789      <address><email></email></address>
2790    </author>
2791    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2792      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2793      <address><email></email></address>
2794    </author>
2795    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2796      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2797      <address><email></email></address>
2798    </author>
2799    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2800      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2801      <address><email></email></address>
2802    </author>
2803    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2804      <organization abbrev="W3C">World Wide Web Consortium</organization>
2805      <address><email></email></address>
2806    </author>
2807    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2808      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2809      <address><email></email></address>
2810    </author>
2811    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2812  </front>
2813  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2814  <x:source href="p6-cache.xml" basename="p6-cache"/>
2817<reference anchor="Part7">
2818  <front>
2819    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2820    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2821      <organization abbrev="Day Software">Day Software</organization>
2822      <address><email></email></address>
2823    </author>
2824    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2825      <organization>One Laptop per Child</organization>
2826      <address><email></email></address>
2827    </author>
2828    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2829      <organization abbrev="HP">Hewlett-Packard Company</organization>
2830      <address><email></email></address>
2831    </author>
2832    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2833      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2834      <address><email></email></address>
2835    </author>
2836    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2837      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2838      <address><email></email></address>
2839    </author>
2840    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2841      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2842      <address><email></email></address>
2843    </author>
2844    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2845      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2846      <address><email></email></address>
2847    </author>
2848    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2849      <organization abbrev="W3C">World Wide Web Consortium</organization>
2850      <address><email></email></address>
2851    </author>
2852    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2853      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2854      <address><email></email></address>
2855    </author>
2856    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2857  </front>
2858  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2859  <x:source href="p7-auth.xml" basename="p7-auth"/>
2862<reference anchor="RFC2119">
2863  <front>
2864    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2865    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2866      <organization>Harvard University</organization>
2867      <address><email></email></address>
2868    </author>
2869    <date month="March" year="1997"/>
2870  </front>
2871  <seriesInfo name="BCP" value="14"/>
2872  <seriesInfo name="RFC" value="2119"/>
2877<references title="Informative References">
2879<reference anchor="RFC1945">
2880  <front>
2881    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2882    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2883      <organization>MIT, Laboratory for Computer Science</organization>
2884      <address><email></email></address>
2885    </author>
2886    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2887      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2888      <address><email></email></address>
2889    </author>
2890    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2891      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2892      <address><email></email></address>
2893    </author>
2894    <date month="May" year="1996"/>
2895  </front>
2896  <seriesInfo name="RFC" value="1945"/>
2899<reference anchor="RFC2068">
2900  <front>
2901    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2902    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2903      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2904      <address><email></email></address>
2905    </author>
2906    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2907      <organization>MIT Laboratory for Computer Science</organization>
2908      <address><email></email></address>
2909    </author>
2910    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2911      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2912      <address><email></email></address>
2913    </author>
2914    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2915      <organization>MIT Laboratory for Computer Science</organization>
2916      <address><email></email></address>
2917    </author>
2918    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2919      <organization>MIT Laboratory for Computer Science</organization>
2920      <address><email></email></address>
2921    </author>
2922    <date month="January" year="1997"/>
2923  </front>
2924  <seriesInfo name="RFC" value="2068"/>
2927<reference anchor="RFC2616">
2928  <front>
2929    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2930    <author initials="R." surname="Fielding" fullname="R. Fielding">
2931      <organization>University of California, Irvine</organization>
2932      <address><email></email></address>
2933    </author>
2934    <author initials="J." surname="Gettys" fullname="J. Gettys">
2935      <organization>W3C</organization>
2936      <address><email></email></address>
2937    </author>
2938    <author initials="J." surname="Mogul" fullname="J. Mogul">
2939      <organization>Compaq Computer Corporation</organization>
2940      <address><email></email></address>
2941    </author>
2942    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2943      <organization>MIT Laboratory for Computer Science</organization>
2944      <address><email></email></address>
2945    </author>
2946    <author initials="L." surname="Masinter" fullname="L. Masinter">
2947      <organization>Xerox Corporation</organization>
2948      <address><email></email></address>
2949    </author>
2950    <author initials="P." surname="Leach" fullname="P. Leach">
2951      <organization>Microsoft Corporation</organization>
2952      <address><email></email></address>
2953    </author>
2954    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2955      <organization>W3C</organization>
2956      <address><email></email></address>
2957    </author>
2958    <date month="June" year="1999"/>
2959  </front>
2960  <seriesInfo name="RFC" value="2616"/>
2963<reference anchor='RFC2817'>
2964  <front>
2965    <title>Upgrading to TLS Within HTTP/1.1</title>
2966    <author initials='R.' surname='Khare' fullname='R. Khare'>
2967      <organization>4K Associates / UC Irvine</organization>
2968      <address><email></email></address>
2969    </author>
2970    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
2971      <organization>Agranat Systems, Inc.</organization>
2972      <address><email></email></address>
2973    </author>
2974    <date year='2000' month='May' />
2975  </front>
2976  <seriesInfo name='RFC' value='2817' />
2979<reference anchor='RFC3864'>
2980  <front>
2981    <title>Registration Procedures for Message Header Fields</title>
2982    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
2983      <organization>Nine by Nine</organization>
2984      <address><email></email></address>
2985    </author>
2986    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
2987      <organization>BEA Systems</organization>
2988      <address><email></email></address>
2989    </author>
2990    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
2991      <organization>HP Labs</organization>
2992      <address><email></email></address>
2993    </author>
2994    <date year='2004' month='September' />
2995  </front>
2996  <seriesInfo name='BCP' value='90' />
2997  <seriesInfo name='RFC' value='3864' />
3000<reference anchor='RFC5226'>
3001  <front>
3002    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3003    <author initials='T.' surname='Narten' fullname='T. Narten'>
3004      <organization>IBM</organization>
3005      <address><email></email></address>
3006    </author>
3007    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3008      <organization>Google</organization>
3009      <address><email></email></address>
3010    </author>
3011    <date year='2008' month='May' />
3012  </front>
3013  <seriesInfo name='BCP' value='26' />
3014  <seriesInfo name='RFC' value='5226' />
3017<reference anchor="RFC5322">
3018  <front>
3019    <title>Internet Message Format</title>
3020    <author initials="P." surname="Resnick" fullname="P. Resnick">
3021      <organization>Qualcomm Incorporated</organization>
3022    </author>
3023    <date year="2008" month="October"/>
3024  </front>
3025  <seriesInfo name="RFC" value="5322"/>
3030<section title="Compatibility with Previous Versions" anchor="compatibility">
3031<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3033   Clarified which error code should be used for inbound server failures
3034   (e.g. DNS failures). (<xref target="status.504"/>).
3037   201 (Created) had a race that required an Etag be sent when a resource is
3038   first created. (<xref target="status.201"/>).
3041   Rewrite of message transmission requirements to make it much harder
3042   for implementors to get it wrong, as the consequences of errors here
3043   can have significant impact on the Internet, and to deal with the
3044   following problems:
3045  <list style="numbers">
3046      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3047         this was incorrectly placing a requirement on the behavior of
3048         an implementation of a future version of HTTP/1.x</t>
3050      <t>Made it clear that user-agents should retry requests, not
3051         "clients" in general.</t>
3053      <t>Converted requirements for clients to ignore unexpected 100
3054         (Continue) responses, and for proxies to forward 100 responses,
3055         into a general requirement for 1xx responses.</t>
3057      <t>Modified some TCP-specific language, to make it clearer that
3058         non-TCP transports are possible for HTTP.</t>
3060      <t>Require that the origin server &MUST-NOT; wait for the request
3061         body before it sends a required 100 (Continue) response.</t>
3063      <t>Allow, rather than require, a server to omit 100 (Continue) if
3064         it has already seen some of the request body.</t>
3066      <t>Allow servers to defend against denial-of-service attacks and
3067         broken clients.</t>
3068  </list>
3071   This change adds the Expect header and 417 status code.
3074   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3075   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3078   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
3079   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3083<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3085  This document takes over the Status Code Registry, previously defined
3086  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3087  (<xref target="status.code.registry"/>)
3090  Clarify definition of POST.
3091  (<xref target="POST"/>)
3094  Failed to consider that there are
3095  many other request methods that are safe to automatically redirect,
3096  and further that the user agent is able to make that determination
3097  based on the request method semantics.
3098  (Sections <xref format="counter" target="status.301"/>,
3099  <xref format="counter" target="status.302"/> and
3100  <xref format="counter" target="status.307"/>)
3103  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3104  It used to indicate that the requested resource must be accessed through the
3105  proxy given by the Location field. The Location field gave the URI of the
3106  proxy. The recipient was expected to repeat this single request via the proxy.
3107  (<xref target="status.305"/>)
3110  Reclassify Allow header as response header, removing the option to
3111  specify it in a PUT request.
3112  Relax the server requirement on the contents of the Allow header and
3113  remove requirement on clients to always trust the header value.
3114  (<xref target="header.allow"/>)
3117  Correct syntax of Location header to allow fragment,
3118  as referred symbol wasn't what was expected, and add some
3119  clarifications as to when it would not be appropriate.
3120  (<xref target="header.location"/>)
3123  In the description of the Server header, the Via field
3124  was described as a SHOULD. The requirement was and is stated
3125  correctly in the description of the Via header in &header-via;.
3126  (<xref target="header.server"/>)
3132<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3134<section title="Since RFC2616">
3136  Extracted relevant partitions from <xref target="RFC2616"/>.
3140<section title="Since draft-ietf-httpbis-p2-semantics-00">
3142  Closed issues:
3143  <list style="symbols">
3144    <t>
3145      <eref target=""/>:
3146      "Via is a MUST"
3147      (<eref target=""/>)
3148    </t>
3149    <t>
3150      <eref target=""/>:
3151      "Fragments allowed in Location"
3152      (<eref target=""/>)
3153    </t>
3154    <t>
3155      <eref target=""/>:
3156      "Safe Methods vs Redirection"
3157      (<eref target=""/>)
3158    </t>
3159    <t>
3160      <eref target=""/>:
3161      "Revise description of the POST method"
3162      (<eref target=""/>)
3163    </t>
3164    <t>
3165      <eref target=""/>:
3166      "Normative and Informative references"
3167    </t>
3168    <t>
3169      <eref target=""/>:
3170      "RFC2606 Compliance"
3171    </t>
3172    <t>
3173      <eref target=""/>:
3174      "Informative references"
3175    </t>
3176    <t>
3177      <eref target=""/>:
3178      "Redundant cross-references"
3179    </t>
3180  </list>
3183  Other changes:
3184  <list style="symbols">
3185    <t>
3186      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3187    </t>
3188  </list>
3192<section title="Since draft-ietf-httpbis-p2-semantics-01">
3194  Closed issues:
3195  <list style="symbols">
3196    <t>
3197      <eref target=""/>:
3198      "PUT side effects"
3199    </t>
3200    <t>
3201      <eref target=""/>:
3202      "Duplicate Host header requirements"
3203    </t>
3204  </list>
3207  Ongoing work on ABNF conversion (<eref target=""/>):
3208  <list style="symbols">
3209    <t>
3210      Move "Product Tokens" section (back) into Part 1, as "token" is used
3211      in the definition of the Upgrade header.
3212    </t>
3213    <t>
3214      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3215    </t>
3216    <t>
3217      Copy definition of delta-seconds from Part6 instead of referencing it.
3218    </t>
3219  </list>
3223<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3225  Closed issues:
3226  <list style="symbols">
3227    <t>
3228      <eref target=""/>:
3229      "Requiring Allow in 405 responses"
3230    </t>
3231    <t>
3232      <eref target=""/>:
3233      "Status Code Registry"
3234    </t>
3235    <t>
3236      <eref target=""/>:
3237      "Redirection vs. Location"
3238    </t>
3239    <t>
3240      <eref target=""/>:
3241      "Cacheability of 303 response"
3242    </t>
3243    <t>
3244      <eref target=""/>:
3245      "305 Use Proxy"
3246    </t>
3247    <t>
3248      <eref target=""/>:
3249      "Classification for Allow header"
3250    </t>
3251    <t>
3252      <eref target=""/>:
3253      "PUT - 'store under' vs 'store at'"
3254    </t>
3255  </list>
3258  Ongoing work on IANA Message Header Registration (<eref target=""/>):
3259  <list style="symbols">
3260    <t>
3261      Reference RFC 3984, and update header registrations for headers defined
3262      in this document.
3263    </t>
3264  </list>
3267  Ongoing work on ABNF conversion (<eref target=""/>):
3268  <list style="symbols">
3269    <t>
3270      Replace string literals when the string really is case-sensitive (method).
3271    </t>
3272  </list>
3276<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3278  Closed issues:
3279  <list style="symbols">
3280    <t>
3281      <eref target=""/>:
3282      "OPTIONS request bodies"
3283    </t>
3284    <t>
3285      <eref target=""/>:
3286      "Description of CONNECT should refer to RFC2817"
3287    </t>
3288    <t>
3289      <eref target=""/>:
3290      "Location Content-Location reference request/response mixup"
3291    </t>
3292  </list>
3295  Ongoing work on Method Registry (<eref target=""/>):
3296  <list style="symbols">
3297    <t>
3298      Added initial proposal for registration process, plus initial
3299      content (non-HTTP/1.1 methods to be added by a separate specification).
3300    </t>
3301  </list>
3305<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3307  Closed issues:
3308  <list style="symbols">
3309    <t>
3310      <eref target=""/>:
3311      "Content-*"
3312    </t>
3313    <t>
3314      <eref target=""/>:
3315      "RFC 2822 is updated by RFC 5322"
3316    </t>
3317  </list>
3320  Ongoing work on ABNF conversion (<eref target=""/>):
3321  <list style="symbols">
3322    <t>
3323      Use "/" instead of "|" for alternatives.
3324    </t>
3325  </list>
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