source: draft-ietf-httpbis/latest/p2-semantics.xml @ 421

Last change on this file since 421 was 421, checked in by julian.reschke@…, 14 years ago

add collected abnf appendices (related to #36)

  • Property svn:eol-style set to native
File size: 150.0 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.05"/>.
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="CR"/>
293  <x:anchor-alias value="DIGIT"/>
294  <x:anchor-alias value="LF"/>
295  <x:anchor-alias value="obs-text"/>
296  <x:anchor-alias value="quoted-string"/>
297  <x:anchor-alias value="token"/>
298  <x:anchor-alias value="OWS"/>
299  <x:anchor-alias value="RWS"/>
300  <x:anchor-alias value="VCHAR"/>
301  <x:anchor-alias value="WSP"/>
303  This specification uses the ABNF syntax defined in &notation-abnf; and
304  the core rules defined in &basic-rules;:
306<figure><artwork type="abnf2616">
307  <x:ref>CR</x:ref>            = &lt;CR, defined in &basic-rules;&gt;
308  <x:ref>DIGIT</x:ref>         = &lt;DIGIT, defined in &basic-rules;&gt;
309  <x:ref>LF</x:ref>            = &lt;LF, defined in &basic-rules;&gt;
310  <x:ref>VCHAR</x:ref>         = &lt;VCHAR, defined in &basic-rules;&gt;
311  <x:ref>WSP</x:ref>           = &lt;WSP, defined in &basic-rules;&gt;
313<figure><artwork type="abnf2616">
314  <x:ref>comment</x:ref>       = &lt;comment, defined in &basic-rules;&gt;
315  <x:ref>quoted-string</x:ref> = &lt;quoted-string, defined in &basic-rules;&gt;
316  <x:ref>token</x:ref>         = &lt;token, defined in &basic-rules;&gt;
317  <x:ref>OWS</x:ref>           = &lt;OWS, defined in &basic-rules;&gt;
318  <x:ref>RWS</x:ref>           = &lt;RWS, defined in &basic-rules;&gt;
319  <x:ref>obs-text</x:ref>      = &lt;obs-text, defined in &basic-rules;&gt;
321<t anchor="abnf.dependencies">
322  <x:anchor-alias value="absolute-URI"/>
323  <x:anchor-alias value="Accept"/>
324  <x:anchor-alias value="Accept-Charset"/>
325  <x:anchor-alias value="Accept-Encoding"/>
326  <x:anchor-alias value="Accept-Language"/>
327  <x:anchor-alias value="Accept-Ranges"/>
328  <x:anchor-alias value="Age"/>
329  <x:anchor-alias value="Authorization"/>
330  <x:anchor-alias value="ETag"/>
331  <x:anchor-alias value="fragment"/>
332  <x:anchor-alias value="Host"/>
333  <x:anchor-alias value="HTTP-date"/>
334  <x:anchor-alias value="If-Match"/>
335  <x:anchor-alias value="If-Modified-Since"/>
336  <x:anchor-alias value="If-None-Match"/>
337  <x:anchor-alias value="If-Range"/>
338  <x:anchor-alias value="If-Unmodified-Since"/>
339  <x:anchor-alias value="partial-URI"/>
340  <x:anchor-alias value="product"/>
341  <x:anchor-alias value="Proxy-Authenticate"/>
342  <x:anchor-alias value="Proxy-Authorization"/>
343  <x:anchor-alias value="Range"/>
344  <x:anchor-alias value="TE"/>
345  <x:anchor-alias value="Vary"/>
346  <x:anchor-alias value="WWW-Authenticate"/>
347  The ABNF rules below are defined in other parts:
349<figure><!--Part1--><artwork type="abnf2616">
350  <x:ref>absolute-URI</x:ref>  = &lt;absolute-URI, defined in &uri;&gt;
351  <x:ref>fragment</x:ref>      = &lt;fragment, defined in &uri;&gt;
352  <x:ref>Host</x:ref>          = &lt;Host, defined in &uri;&gt;
353  <x:ref>HTTP-date</x:ref>     = &lt;HTTP-date, defined in &full-date;&gt;
354  <x:ref>partial-URI</x:ref>   = &lt;partial-URI, defined in &uri;&gt;
355  <x:ref>product</x:ref>       = &lt;product, defined in &product-tokens;&gt;
356  <x:ref>TE</x:ref>            = &lt;TE, defined in &header-te;&gt;
358<figure><!--Part3--><artwork type="abnf2616">
359  <x:ref>Accept</x:ref>        = &lt;Accept, defined in &header-accept;&gt;
360  <x:ref>Accept-Charset</x:ref> =
361             &lt;Accept-Charset, defined in &header-accept-charset;&gt;
362  <x:ref>Accept-Encoding</x:ref> =
363             &lt;Accept-Encoding, defined in &header-accept-encoding;&gt;
364  <x:ref>Accept-Language</x:ref> =
365             &lt;Accept-Language, defined in &header-accept-language;&gt;
367<figure><!--Part4--><artwork type="abnf2616">
368  <x:ref>ETag</x:ref>          = &lt;ETag, defined in &header-etag;&gt;
369  <x:ref>If-Match</x:ref>      = &lt;If-Match, defined in &header-if-match;&gt;
370  <x:ref>If-Modified-Since</x:ref> =
371             &lt;If-Modified-Since, defined in &header-if-modified-since;&gt;
372  <x:ref>If-None-Match</x:ref> = &lt;If-None-Match, defined in &header-if-none-match;&gt;
373  <x:ref>If-Unmodified-Since</x:ref> =
374             &lt;If-Unmodified-Since, defined in &header-if-unmodified-since;&gt;
376<figure><!--Part5--><artwork type="abnf2616">
377  <x:ref>Accept-Ranges</x:ref> = &lt;Accept-Ranges, defined in &header-accept-ranges;&gt;
378  <x:ref>If-Range</x:ref>      = &lt;If-Range, defined in &header-if-range;&gt;
379  <x:ref>Range</x:ref>         = &lt;Range, defined in &header-range;&gt;
381<figure><!--Part6--><artwork type="abnf2616">
382  <x:ref>Age</x:ref>           = &lt;Age, defined in &header-age;&gt;
383  <x:ref>Vary</x:ref>          = &lt;Vary, defined in &header-vary;&gt;
385<figure><artwork type="abnf2616">
386  <x:ref>Authorization</x:ref> = &lt;Authorization, defined in &header-authorization;&gt;
387  <x:ref>Proxy-Authenticate</x:ref> =
388             &lt;Proxy-Authenticate, defined in &header-proxy-authenticate;&gt;
389  <x:ref>Proxy-Authorization</x:ref> =
390             &lt;Proxy-Authorization, defined in &header-proxy-authorization;&gt;
391  <x:ref>WWW-Authenticate</x:ref> =
392             &lt;WWW-Authenticate, defined in &header-www-authenticate;&gt;
396<section title="Method" anchor="method">
397  <x:anchor-alias value="Method"/>
398  <x:anchor-alias value="extension-method"/>
400   The Method  token indicates the method to be performed on the
401   resource identified by the request-target. The method is case-sensitive.
403<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Method"/><iref primary="true" item="Grammar" subitem="extension-method"/>
404  <x:ref>Method</x:ref>         = <x:abnf-char-sequence>"OPTIONS"</x:abnf-char-sequence>   ; "OPTIONS", <xref target="OPTIONS"/>
405                 / <x:abnf-char-sequence>"GET"</x:abnf-char-sequence>               ; "GET", <xref target="GET"/>
406                 / <x:abnf-char-sequence>"HEAD"</x:abnf-char-sequence>            ; "HEAD", <xref target="HEAD"/>
407                 / <x:abnf-char-sequence>"POST"</x:abnf-char-sequence>            ; "POST", <xref target="POST"/>
408                 / <x:abnf-char-sequence>"PUT"</x:abnf-char-sequence>               ; "PUT", <xref target="PUT"/>
409                 / <x:abnf-char-sequence>"DELETE"</x:abnf-char-sequence>      ; "DELETE", <xref target="DELETE"/>
410                 / <x:abnf-char-sequence>"TRACE"</x:abnf-char-sequence>         ; "TRACE", <xref target="TRACE"/>
411                 / <x:abnf-char-sequence>"CONNECT"</x:abnf-char-sequence>   ; "CONNECT", <xref target="CONNECT"/>
412                 / <x:ref>extension-method</x:ref>
413  <x:ref>extension-method</x:ref> = <x:ref>token</x:ref>
416   The list of methods allowed by a resource can be specified in an
417   Allow header field (<xref target="header.allow"/>). The return code of the response
418   always notifies the client whether a method is currently allowed on a
419   resource, since the set of allowed methods can change dynamically. An
420   origin server &SHOULD; return the status code 405 (Method Not Allowed)
421   if the method is known by the origin server but not allowed for the
422   requested resource, and 501 (Not Implemented) if the method is
423   unrecognized or not implemented by the origin server. The methods GET
424   and HEAD &MUST; be supported by all general-purpose servers. All other
425   methods are &OPTIONAL;; however, if the above methods are implemented,
426   they &MUST; be implemented with the same semantics as those specified
427   in <xref target="method.definitions"/>.
430<section title="Method Registry" anchor="method.registry">
432  The HTTP Method Registry defines the name space for the Method token in the
433  Request line of an HTTP request.
436  Registrations &MUST; include the following fields:
437  <list style="symbols">
438    <t>Method Name (see <xref target="method"/>)</t>
439    <t>Safe ("yes" or "no", see <xref target="safe.methods"/>)</t>
440    <t>Pointer to specification text</t>
441  </list>
444  Values to be added to this name space are subject to IETF review
445  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
446  new method names should be traceable through statuses of either 'Obsoletes'
447  or 'Updates' to this document.
450  The registry itself is maintained at <eref target=""/>.
455<section title="Request Header Fields" anchor="request.header.fields">
456  <x:anchor-alias value="extension-code"/>
457  <x:anchor-alias value="request-header"/>
459   The request-header fields allow the client to pass additional
460   information about the request, and about the client itself, to the
461   server. These fields act as request modifiers, with semantics
462   equivalent to the parameters on a programming language method
463   invocation.
465<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="request-header"/>
466  <x:ref>request-header</x:ref> = <x:ref>Accept</x:ref>                   ; &header-accept;
467                 / <x:ref>Accept-Charset</x:ref>           ; &header-accept-charset;
468                 / <x:ref>Accept-Encoding</x:ref>          ; &header-accept-encoding;
469                 / <x:ref>Accept-Language</x:ref>          ; &header-accept-language;
470                 / <x:ref>Authorization</x:ref>            ; &header-authorization;
471                 / <x:ref>Expect</x:ref>                   ; <xref target="header.expect"/>
472                 / <x:ref>From</x:ref>                     ; <xref target="header.from"/>
473                 / <x:ref>Host</x:ref>                     ; &header-host;
474                 / <x:ref>If-Match</x:ref>                 ; &header-if-match;
475                 / <x:ref>If-Modified-Since</x:ref>        ; &header-if-modified-since;
476                 / <x:ref>If-None-Match</x:ref>            ; &header-if-none-match;
477                 / <x:ref>If-Range</x:ref>                 ; &header-if-range;
478                 / <x:ref>If-Unmodified-Since</x:ref>      ; &header-if-unmodified-since;
479                 / <x:ref>Max-Forwards</x:ref>             ; <xref target="header.max-forwards"/>
480                 / <x:ref>Proxy-Authorization</x:ref>      ; &header-proxy-authorization;
481                 / <x:ref>Range</x:ref>                    ; &header-range;
482                 / <x:ref>Referer</x:ref>                  ; <xref target="header.referer"/>
483                 / <x:ref>TE</x:ref>                       ; &header-te;
484                 / <x:ref>User-Agent</x:ref>               ; <xref target="header.user-agent"/>
487   Request-header field names can be extended reliably only in
488   combination with a change in the protocol version. However, new or
489   experimental header fields &MAY; be given the semantics of request-header
490   fields if all parties in the communication recognize them to
491   be request-header fields. Unrecognized header fields are treated as
492   entity-header fields.
496<section title="Status Code and Reason Phrase" anchor="status.code.and.reason.phrase">
497  <x:anchor-alias value="Reason-Phrase"/>
498  <x:anchor-alias value="Status-Code"/>
500   The Status-Code element is a 3-digit integer result code of the
501   attempt to understand and satisfy the request. The status codes listed
502   below are defined in <xref target=""/>.
503   The Reason-Phrase is intended to give a short
504   textual description of the Status-Code. The Status-Code is intended
505   for use by automata and the Reason-Phrase is intended for the human
506   user. The client is not required to examine or display the Reason-Phrase.
509   The individual values of the numeric status codes defined for
510   HTTP/1.1, and an example set of corresponding Reason-Phrase's, are
511   presented below. The reason phrases listed here are only
512   recommendations -- they &MAY; be replaced by local equivalents without
513   affecting the protocol.
515<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"/>
516  <x:ref>Status-Code</x:ref>    =
517         "100"  ; <xref target="status.100"/>: Continue
518       / "101"  ; <xref target="status.101"/>: Switching Protocols
519       / "200"  ; <xref target="status.200"/>: OK
520       / "201"  ; <xref target="status.201"/>: Created
521       / "202"  ; <xref target="status.202"/>: Accepted
522       / "203"  ; <xref target="status.203"/>: Non-Authoritative Information
523       / "204"  ; <xref target="status.204"/>: No Content
524       / "205"  ; <xref target="status.205"/>: Reset Content
525       / "206"  ; <xref target="status.206"/>: Partial Content
526       / "300"  ; <xref target="status.300"/>: Multiple Choices
527       / "301"  ; <xref target="status.301"/>: Moved Permanently
528       / "302"  ; <xref target="status.302"/>: Found
529       / "303"  ; <xref target="status.303"/>: See Other
530       / "304"  ; <xref target="status.304"/>: Not Modified
531       / "305"  ; <xref target="status.305"/>: Use Proxy
532       / "307"  ; <xref target="status.307"/>: Temporary Redirect
533       / "400"  ; <xref target="status.400"/>: Bad Request
534       / "401"  ; <xref target="status.401"/>: Unauthorized
535       / "402"  ; <xref target="status.402"/>: Payment Required
536       / "403"  ; <xref target="status.403"/>: Forbidden
537       / "404"  ; <xref target="status.404"/>: Not Found
538       / "405"  ; <xref target="status.405"/>: Method Not Allowed
539       / "406"  ; <xref target="status.406"/>: Not Acceptable
540       / "407"  ; <xref target="status.407"/>: Proxy Authentication Required
541       / "408"  ; <xref target="status.408"/>: Request Time-out
542       / "409"  ; <xref target="status.409"/>: Conflict
543       / "410"  ; <xref target="status.410"/>: Gone
544       / "411"  ; <xref target="status.411"/>: Length Required
545       / "412"  ; <xref target="status.412"/>: Precondition Failed
546       / "413"  ; <xref target="status.413"/>: Request Entity Too Large
547       / "414"  ; <xref target="status.414"/>: Request-target Too Large
548       / "415"  ; <xref target="status.415"/>: Unsupported Media Type
549       / "416"  ; <xref target="status.416"/>: Requested range not satisfiable
550       / "417"  ; <xref target="status.417"/>: Expectation Failed
551       / "500"  ; <xref target="status.500"/>: Internal Server Error
552       / "501"  ; <xref target="status.501"/>: Not Implemented
553       / "502"  ; <xref target="status.502"/>: Bad Gateway
554       / "503"  ; <xref target="status.503"/>: Service Unavailable
555       / "504"  ; <xref target="status.504"/>: Gateway Time-out
556       / "505"  ; <xref target="status.505"/>: HTTP Version not supported
557       / <x:ref>extension-code</x:ref>
559  <x:ref>extension-code</x:ref> = 3<x:ref>DIGIT</x:ref>
560  <x:ref>Reason-Phrase</x:ref>  = *( <x:ref>WSP</x:ref> / <x:ref>VCHAR</x:ref> / <x:ref>obs-text</x:ref> )
563   HTTP status codes are extensible. HTTP applications are not required
564   to understand the meaning of all registered status codes, though such
565   understanding is obviously desirable. However, applications &MUST;
566   understand the class of any status code, as indicated by the first
567   digit, and treat any unrecognized response as being equivalent to the
568   x00 status code of that class, with the exception that an
569   unrecognized response &MUST-NOT; be cached. For example, if an
570   unrecognized status code of 431 is received by the client, it can
571   safely assume that there was something wrong with its request and
572   treat the response as if it had received a 400 status code. In such
573   cases, user agents &SHOULD; present to the user the entity returned
574   with the response, since that entity is likely to include human-readable
575   information which will explain the unusual status.
578<section title="Status Code Registry" anchor="status.code.registry">
580  The HTTP Status Code Registry defines the name space for the Status-Code
581  token in the Status line of an HTTP response.
584  Values to be added to this name space are subject to IETF review
585  (<xref target="RFC5226" x:fmt="," x:sec="4.1"/>).  Any document registering
586  new status codes should be traceable through statuses of either 'Obsoletes'
587  or 'Updates' to this document.
590  The registry itself is maintained at <eref target=""/>.
596<section title="Response Header Fields" anchor="response.header.fields">
597  <x:anchor-alias value="response-header"/>
599   The response-header fields allow the server to pass additional
600   information about the response which cannot be placed in the Status-Line.
601   These header fields give information about the server and about
602   further access to the resource identified by the request-target.
604<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="response-header"/>
605  <x:ref>response-header</x:ref> = <x:ref>Accept-Ranges</x:ref>           ; &header-accept-ranges;
606                  / <x:ref>Age</x:ref>                     ; &header-age;
607                  / <x:ref>Allow</x:ref>                   ; <xref target="header.allow"/>
608                  / <x:ref>ETag</x:ref>                    ; &header-etag;
609                  / <x:ref>Location</x:ref>                ; <xref target="header.location"/>
610                  / <x:ref>Proxy-Authenticate</x:ref>      ; &header-proxy-authenticate;
611                  / <x:ref>Retry-After</x:ref>             ; <xref target="header.retry-after"/>
612                  / <x:ref>Server</x:ref>                  ; <xref target="header.server"/>
613                  / <x:ref>Vary</x:ref>                    ; &header-vary;
614                  / <x:ref>WWW-Authenticate</x:ref>        ; &header-www-authenticate;
617   Response-header field names can be extended reliably only in
618   combination with a change in the protocol version. However, new or
619   experimental header fields &MAY; be given the semantics of response-header
620   fields if all parties in the communication recognize them to
621   be response-header fields. Unrecognized header fields are treated as
622   entity-header fields.
626<section title="Entity" anchor="entity">
628   Request and Response messages &MAY; transfer an entity if not otherwise
629   restricted by the request method or response status code. An entity
630   consists of entity-header fields and an entity-body, although some
631   responses will only include the entity-headers. HTTP entity-body and
632   entity-header fields are defined in &payload;.
635   An entity-body is only present in a message when a message-body is
636   present, as described in &message-body;. The entity-body is obtained
637   from the message-body by decoding any Transfer-Encoding that might
638   have been applied to ensure safe and proper transfer of the message.
643<section title="Method Definitions" anchor="method.definitions">
645   The set of common methods for HTTP/1.1 is defined below. Although
646   this set can be expanded, additional methods cannot be assumed to
647   share the same semantics for separately extended clients and servers.
650<section title="Safe and Idempotent Methods" anchor="safe.and.idempotent">
652<section title="Safe Methods" anchor="safe.methods">
653<iref item="Safe Methods" primary="true"/>
655   Implementors should be aware that the software represents the user in
656   their interactions over the Internet, and should be careful to allow
657   the user to be aware of any actions they might take which may have an
658   unexpected significance to themselves or others.
661   In particular, the convention has been established that the GET and
662   HEAD methods &SHOULD-NOT;  have the significance of taking an action
663   other than retrieval. These methods ought to be considered "<x:dfn anchor="safe">safe</x:dfn>".
664   This allows user agents to represent other methods, such as POST, PUT
665   and DELETE, in a special way, so that the user is made aware of the
666   fact that a possibly unsafe action is being requested.
669   Naturally, it is not possible to ensure that the server does not
670   generate side-effects as a result of performing a GET request; in
671   fact, some dynamic resources consider that a feature. The important
672   distinction here is that the user did not request the side-effects,
673   so therefore cannot be held accountable for them.
677<section title="Idempotent Methods" anchor="idempotent.methods">
678<iref item="Idempotent Methods" primary="true"/>
680   Methods can also have the property of "idempotence" in that (aside
681   from error or expiration issues) the side-effects of N &gt; 0 identical
682   requests is the same as for a single request. The methods GET, HEAD,
683   PUT and DELETE share this property. Also, the methods OPTIONS and
684   TRACE &SHOULD-NOT;  have side effects, and so are inherently idempotent.
687   However, it is possible that a sequence of several requests is non-idempotent,
688   even if all of the methods executed in that sequence are
689   idempotent. (A sequence is idempotent if a single execution of the
690   entire sequence always yields a result that is not changed by a
691   reexecution of all, or part, of that sequence.) For example, a
692   sequence is non-idempotent if its result depends on a value that is
693   later modified in the same sequence.
696   A sequence that never has side effects is idempotent, by definition
697   (provided that no concurrent operations are being executed on the
698   same set of resources).
703<section title="OPTIONS" anchor="OPTIONS">
704  <rdf:Description>
705    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
706  </rdf:Description>
707  <iref primary="true" item="OPTIONS method" x:for-anchor=""/>
708  <iref primary="true" item="Methods" subitem="OPTIONS" x:for-anchor=""/>
710   The OPTIONS method represents a request for information about the
711   communication options available on the request/response chain
712   identified by the request-target. This method allows the client to
713   determine the options and/or requirements associated with a resource,
714   or the capabilities of a server, without implying a resource action
715   or initiating a resource retrieval.
718   Responses to this method are not cacheable.
721   If the OPTIONS request includes an entity-body (as indicated by the
722   presence of Content-Length or Transfer-Encoding), then the media type
723   &MUST; be indicated by a Content-Type field. Although this
724   specification does not define any use for such a body, future
725   extensions to HTTP might use the OPTIONS body to make more detailed
726   queries on the server.
729   If the request-target is an asterisk ("*"), the OPTIONS request is
730   intended to apply to the server in general rather than to a specific
731   resource. Since a server's communication options typically depend on
732   the resource, the "*" request is only useful as a "ping" or "no-op"
733   type of method; it does nothing beyond allowing the client to test
734   the capabilities of the server. For example, this can be used to test
735   a proxy for HTTP/1.1 compliance (or lack thereof).
738   If the request-target is not an asterisk, the OPTIONS request applies
739   only to the options that are available when communicating with that
740   resource.
743   A 200 response &SHOULD; include any header fields that indicate
744   optional features implemented by the server and applicable to that
745   resource (e.g., Allow), possibly including extensions not defined by
746   this specification. The response body, if any, &SHOULD; also include
747   information about the communication options. The format for such a
748   body is not defined by this specification, but might be defined by
749   future extensions to HTTP. Content negotiation &MAY; be used to select
750   the appropriate response format. If no response body is included, the
751   response &MUST; include a Content-Length field with a field-value of
752   "0".
755   The Max-Forwards request-header field &MAY; be used to target a
756   specific proxy in the request chain. When a proxy receives an OPTIONS
757   request on an absolute-URI for which request forwarding is permitted,
758   the proxy &MUST; check for a Max-Forwards field. If the Max-Forwards
759   field-value is zero ("0"), the proxy &MUST-NOT; forward the message;
760   instead, the proxy &SHOULD; respond with its own communication options.
761   If the Max-Forwards field-value is an integer greater than zero, the
762   proxy &MUST; decrement the field-value when it forwards the request. If
763   no Max-Forwards field is present in the request, then the forwarded
764   request &MUST-NOT; include a Max-Forwards field.
768<section title="GET" anchor="GET">
769  <rdf:Description>
770    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
771  </rdf:Description>
772  <iref primary="true" item="GET method" x:for-anchor=""/>
773  <iref primary="true" item="Methods" subitem="GET" x:for-anchor=""/>
775   The GET method means retrieve whatever information (in the form of an
776   entity) is identified by the request-target. If the request-target refers
777   to a data-producing process, it is the produced data which shall be
778   returned as the entity in the response and not the source text of the
779   process, unless that text happens to be the output of the process.
782   The semantics of the GET method change to a "conditional GET" if the
783   request message includes an If-Modified-Since, If-Unmodified-Since,
784   If-Match, If-None-Match, or If-Range header field. A conditional GET
785   method requests that the entity be transferred only under the
786   circumstances described by the conditional header field(s). The
787   conditional GET method is intended to reduce unnecessary network
788   usage by allowing cached entities to be refreshed without requiring
789   multiple requests or transferring data already held by the client.
792   The semantics of the GET method change to a "partial GET" if the
793   request message includes a Range header field. A partial GET requests
794   that only part of the entity be transferred, as described in &header-range;.
795   The partial GET method is intended to reduce unnecessary
796   network usage by allowing partially-retrieved entities to be
797   completed without transferring data already held by the client.
800   The response to a GET request is cacheable if and only if it meets
801   the requirements for HTTP caching described in &caching;.
804   See <xref target=""/> for security considerations when used for forms.
808<section title="HEAD" anchor="HEAD">
809  <rdf:Description>
810    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
811  </rdf:Description>
812  <iref primary="true" item="HEAD method" x:for-anchor=""/>
813  <iref primary="true" item="Methods" subitem="HEAD" x:for-anchor=""/>
815   The HEAD method is identical to GET except that the server &MUST-NOT;
816   return a message-body in the response. The metainformation contained
817   in the HTTP headers in response to a HEAD request &SHOULD; be identical
818   to the information sent in response to a GET request. This method can
819   be used for obtaining metainformation about the entity implied by the
820   request without transferring the entity-body itself. This method is
821   often used for testing hypertext links for validity, accessibility,
822   and recent modification.
825   The response to a HEAD request &MAY; be cacheable in the sense that the
826   information contained in the response &MAY; be used to update a
827   previously cached entity from that resource. If the new field values
828   indicate that the cached entity differs from the current entity (as
829   would be indicated by a change in Content-Length, Content-MD5, ETag
830   or Last-Modified), then the cache &MUST; treat the cache entry as
831   stale.
835<section title="POST" anchor="POST">
836  <iref primary="true" item="POST method" x:for-anchor=""/>
837  <iref primary="true" item="Methods" subitem="POST" x:for-anchor=""/>
839   The POST method is used to request that the origin server accept the
840   entity enclosed in the request as data to be processed by the resource
841   identified by the request-target in the Request-Line. POST is designed
842   to allow a uniform method to cover the following functions:
843  <list style="symbols">
844    <t>
845      Annotation of existing resources;
846    </t>
847    <t>
848        Posting a message to a bulletin board, newsgroup, mailing list,
849        or similar group of articles;
850    </t>
851    <t>
852        Providing a block of data, such as the result of submitting a
853        form, to a data-handling process;
854    </t>
855    <t>
856        Extending a database through an append operation.
857    </t>
858  </list>
861   The actual function performed by the POST method is determined by the
862   server and is usually dependent on the request-target.
865   The action performed by the POST method might not result in a
866   resource that can be identified by a URI. In this case, either 200
867   (OK) or 204 (No Content) is the appropriate response status,
868   depending on whether or not the response includes an entity that
869   describes the result.
872   If a resource has been created on the origin server, the response
873   &SHOULD; be 201 (Created) and contain an entity which describes the
874   status of the request and refers to the new resource, and a Location
875   header (see <xref target="header.location"/>).
878   Responses to this method are not cacheable, unless the response
879   includes appropriate Cache-Control or Expires header fields. However,
880   the 303 (See Other) response can be used to direct the user agent to
881   retrieve a cacheable resource.
885<section title="PUT" anchor="PUT">
886  <iref primary="true" item="PUT method" x:for-anchor=""/>
887  <iref primary="true" item="Methods" subitem="PUT" x:for-anchor=""/>
889   The PUT method requests that the enclosed entity be stored at the
890   supplied request-target. If the request-target refers to an already
891   existing resource, the enclosed entity &SHOULD; be considered as a
892   modified version of the one residing on the origin server. If the
893   request-target does not point to an existing resource, and that URI is
894   capable of being defined as a new resource by the requesting user
895   agent, the origin server can create the resource with that URI. If a
896   new resource is created at the request-target, the origin server &MUST;
897         inform the user agent
898   via the 201 (Created) response. If an existing resource is modified,
899   either the 200 (OK) or 204 (No Content) response codes &SHOULD; be sent
900   to indicate successful completion of the request. If the resource
901   could not be created or modified with the request-target, an appropriate
902   error response &SHOULD; be given that reflects the nature of the
903   problem. The recipient of the entity &MUST-NOT; ignore any Content-*
904   headers (headers starting with the prefix 'Content-') that it does
905   not understand or implement
906   and &MUST; return a 501 (Not Implemented) response in such cases.
909   If the request passes through a cache and the request-target identifies
910   one or more currently cached entities, those entries &SHOULD; be
911   treated as stale. Responses to this method are not cacheable.
914   The fundamental difference between the POST and PUT requests is
915   reflected in the different meaning of the request-target. The URI in a
916   POST request identifies the resource that will handle the enclosed
917   entity. That resource might be a data-accepting process, a gateway to
918   some other protocol, or a separate entity that accepts annotations.
919   In contrast, the URI in a PUT request identifies the entity enclosed
920   with the request -- the user agent knows what URI is intended and the
921   server &MUST-NOT; attempt to apply the request to some other resource.
922   If the server desires that the request be applied to a different URI,
923   it &MUST; send a 301 (Moved Permanently) response; the user agent &MAY;
924   then make its own decision regarding whether or not to redirect the
925   request.
928   A single resource &MAY; be identified by many different URIs. For
929   example, an article might have a URI for identifying "the current
930   version" which is separate from the URI identifying each particular
931   version. In this case, a PUT request on a general URI might result in
932   several other URIs being defined by the origin server.
935   HTTP/1.1 does not define how a PUT method affects the state of an
936   origin server.
939   Unless otherwise specified for a particular entity-header, the
940   entity-headers in the PUT request &SHOULD; be applied to the resource
941   created or modified by the PUT.
945<section title="DELETE" anchor="DELETE">
946  <iref primary="true" item="DELETE method" x:for-anchor=""/>
947  <iref primary="true" item="Methods" subitem="DELETE" x:for-anchor=""/>
949   The DELETE method requests that the origin server delete the resource
950   identified by the request-target. This method &MAY; be overridden by human
951   intervention (or other means) on the origin server. The client cannot
952   be guaranteed that the operation has been carried out, even if the
953   status code returned from the origin server indicates that the action
954   has been completed successfully. However, the server &SHOULD-NOT;
955   indicate success unless, at the time the response is given, it
956   intends to delete the resource or move it to an inaccessible
957   location.
960   A successful response &SHOULD; be 200 (OK) if the response includes an
961   entity describing the status, 202 (Accepted) if the action has not
962   yet been enacted, or 204 (No Content) if the action has been enacted
963   but the response does not include an entity.
966   If the request passes through a cache and the request-target identifies
967   one or more currently cached entities, those entries &SHOULD; be
968   treated as stale. Responses to this method are not cacheable.
972<section title="TRACE" anchor="TRACE">
973  <rdf:Description>
974    <safe xmlns="urn:ietf:id:draft-ietf-httpbis-p2-semantics#">yes</safe>
975  </rdf:Description>
976  <iref primary="true" item="TRACE method" x:for-anchor=""/>
977  <iref primary="true" item="Methods" subitem="TRACE" x:for-anchor=""/>
979   The TRACE method is used to invoke a remote, application-layer loop-back
980   of the request message. The final recipient of the request
981   &SHOULD; reflect the message received back to the client as the
982   entity-body of a 200 (OK) response. The final recipient is either the
983   origin server or the first proxy or gateway to receive a Max-Forwards
984   value of zero (0) in the request (see <xref target="header.max-forwards"/>). A TRACE request
985   &MUST-NOT; include an entity.
988   TRACE allows the client to see what is being received at the other
989   end of the request chain and use that data for testing or diagnostic
990   information. The value of the Via header field (&header-via;) is of
991   particular interest, since it acts as a trace of the request chain.
992   Use of the Max-Forwards header field allows the client to limit the
993   length of the request chain, which is useful for testing a chain of
994   proxies forwarding messages in an infinite loop.
997   If the request is valid, the response &SHOULD; contain the entire
998   request message in the entity-body, with a Content-Type of
999   "message/http" (see &media-type-message-http;). Responses to this method
1000   &MUST-NOT; be cached.
1004<section title="CONNECT" anchor="CONNECT">
1005  <iref primary="true" item="CONNECT method" x:for-anchor=""/>
1006  <iref primary="true" item="Methods" subitem="CONNECT" x:for-anchor=""/>
1008   This specification reserves the method name CONNECT for use with a
1009   proxy that can dynamically switch to being a tunnel (e.g. SSL
1010   tunneling <xref target="RFC2817"/>).
1016<section title="Status Code Definitions" anchor="">
1018   Each Status-Code is described below, including a description of which
1019   method(s) it can follow and any metainformation required in the
1020   response.
1023<section title="Informational 1xx" anchor="status.1xx">
1025   This class of status code indicates a provisional response,
1026   consisting only of the Status-Line and optional headers, and is
1027   terminated by an empty line. There are no required headers for this
1028   class of status code. Since HTTP/1.0 did not define any 1xx status
1029   codes, servers &MUST-NOT; send a 1xx response to an HTTP/1.0 client
1030   except under experimental conditions.
1033   A client &MUST; be prepared to accept one or more 1xx status responses
1034   prior to a regular response, even if the client does not expect a 100
1035   (Continue) status message. Unexpected 1xx status responses &MAY; be
1036   ignored by a user agent.
1039   Proxies &MUST; forward 1xx responses, unless the connection between the
1040   proxy and its client has been closed, or unless the proxy itself
1041   requested the generation of the 1xx response. (For example, if a
1042   proxy adds a "Expect: 100-continue" field when it forwards a request,
1043   then it need not forward the corresponding 100 (Continue)
1044   response(s).)
1047<section title="100 Continue" anchor="status.100">
1048  <iref primary="true" item="100 Continue (status code)" x:for-anchor=""/>
1049  <iref primary="true" item="Status Codes" subitem="100 Continue" x:for-anchor=""/>
1051   The client &SHOULD; continue with its request. This interim response is
1052   used to inform the client that the initial part of the request has
1053   been received and has not yet been rejected by the server. The client
1054   &SHOULD; continue by sending the remainder of the request or, if the
1055   request has already been completed, ignore this response. The server
1056   &MUST; send a final response after the request has been completed. See
1057   &use100; for detailed discussion of the use and handling of this
1058   status code.
1062<section title="101 Switching Protocols" anchor="status.101">
1063  <iref primary="true" item="101 Switching Protocols (status code)" x:for-anchor=""/>
1064  <iref primary="true" item="Status Codes" subitem="101 Switching Protocols" x:for-anchor=""/>
1066   The server understands and is willing to comply with the client's
1067   request, via the Upgrade message header field (&header-upgrade;), for a
1068   change in the application protocol being used on this connection. The
1069   server will switch protocols to those defined by the response's
1070   Upgrade header field immediately after the empty line which
1071   terminates the 101 response.
1074   The protocol &SHOULD; be switched only when it is advantageous to do
1075   so. For example, switching to a newer version of HTTP is advantageous
1076   over older versions, and switching to a real-time, synchronous
1077   protocol might be advantageous when delivering resources that use
1078   such features.
1083<section title="Successful 2xx" anchor="status.2xx">
1085   This class of status code indicates that the client's request was
1086   successfully received, understood, and accepted.
1089<section title="200 OK" anchor="status.200">
1090  <iref primary="true" item="200 OK (status code)" x:for-anchor=""/>
1091  <iref primary="true" item="Status Codes" subitem="200 OK" x:for-anchor=""/>
1093   The request has succeeded. The information returned with the response
1094   is dependent on the method used in the request, for example:
1095  <list style="hanging">
1096    <t hangText="GET">
1097          an entity corresponding to the requested resource is sent in
1098          the response;
1099    </t>
1100    <t hangText="HEAD">
1101          the entity-header fields corresponding to the requested
1102          resource are sent in the response without any message-body;
1103    </t>
1104    <t hangText="POST">
1105      an entity describing or containing the result of the action;
1106    </t>
1107    <t hangText="TRACE">
1108      an entity containing the request message as received by the
1109      end server.
1110    </t>
1111  </list>
1115<section title="201 Created" anchor="status.201">
1116  <iref primary="true" item="201 Created (status code)" x:for-anchor=""/>
1117  <iref primary="true" item="Status Codes" subitem="201 Created" x:for-anchor=""/>
1119   The request has been fulfilled and resulted in a new resource being
1120   created. The newly created resource can be referenced by the URI(s)
1121   returned in the entity of the response, with the most specific URI
1122   for the resource given by a Location header field. The response
1123   &SHOULD; include an entity containing a list of resource
1124   characteristics and location(s) from which the user or user agent can
1125   choose the one most appropriate. The entity format is specified by
1126   the media type given in the Content-Type header field. The origin
1127   server &MUST; create the resource before returning the 201 status code.
1128   If the action cannot be carried out immediately, the server &SHOULD;
1129   respond with 202 (Accepted) response instead.
1132   A 201 response &MAY; contain an ETag response header field indicating
1133   the current value of the entity tag for the requested variant just
1134   created, see &header-etag;.
1138<section title="202 Accepted" anchor="status.202">
1139  <iref primary="true" item="202 Accepted (status code)" x:for-anchor=""/>
1140  <iref primary="true" item="Status Codes" subitem="202 Accepted" x:for-anchor=""/>
1142   The request has been accepted for processing, but the processing has
1143   not been completed.  The request might or might not eventually be
1144   acted upon, as it might be disallowed when processing actually takes
1145   place. There is no facility for re-sending a status code from an
1146   asynchronous operation such as this.
1149   The 202 response is intentionally non-committal. Its purpose is to
1150   allow a server to accept a request for some other process (perhaps a
1151   batch-oriented process that is only run once per day) without
1152   requiring that the user agent's connection to the server persist
1153   until the process is completed. The entity returned with this
1154   response &SHOULD; include an indication of the request's current status
1155   and either a pointer to a status monitor or some estimate of when the
1156   user can expect the request to be fulfilled.
1160<section title="203 Non-Authoritative Information" anchor="status.203">
1161  <iref primary="true" item="203 Non-Authoritative Information (status code)" x:for-anchor=""/>
1162  <iref primary="true" item="Status Codes" subitem="203 Non-Authoritative Information" x:for-anchor=""/>
1164   The returned metainformation in the entity-header is not the
1165   definitive set as available from the origin server, but is gathered
1166   from a local or a third-party copy. The set presented &MAY; be a subset
1167   or superset of the original version. For example, including local
1168   annotation information about the resource might result in a superset
1169   of the metainformation known by the origin server. Use of this
1170   response code is not required and is only appropriate when the
1171   response would otherwise be 200 (OK).
1175<section title="204 No Content" anchor="status.204">
1176  <iref primary="true" item="204 No Content (status code)" x:for-anchor=""/>
1177  <iref primary="true" item="Status Codes" subitem="204 No Content" x:for-anchor=""/>
1179   The server has fulfilled the request but does not need to return an
1180   entity-body, and might want to return updated metainformation. The
1181   response &MAY; include new or updated metainformation in the form of
1182   entity-headers, which if present &SHOULD; be associated with the
1183   requested variant.
1186   If the client is a user agent, it &SHOULD-NOT;  change its document view
1187   from that which caused the request to be sent. This response is
1188   primarily intended to allow input for actions to take place without
1189   causing a change to the user agent's active document view, although
1190   any new or updated metainformation &SHOULD; be applied to the document
1191   currently in the user agent's active view.
1194   The 204 response &MUST-NOT; include a message-body, and thus is always
1195   terminated by the first empty line after the header fields.
1199<section title="205 Reset Content" anchor="status.205">
1200  <iref primary="true" item="205 Reset Content (status code)" x:for-anchor=""/>
1201  <iref primary="true" item="Status Codes" subitem="205 Reset Content" x:for-anchor=""/>
1203   The server has fulfilled the request and the user agent &SHOULD; reset
1204   the document view which caused the request to be sent. This response
1205   is primarily intended to allow input for actions to take place via
1206   user input, followed by a clearing of the form in which the input is
1207   given so that the user can easily initiate another input action. The
1208   response &MUST-NOT; include an entity.
1212<section title="206 Partial Content" anchor="status.206">
1213  <iref primary="true" item="206 Partial Content (status code)" x:for-anchor=""/>
1214  <iref primary="true" item="Status Codes" subitem="206 Partial Content" x:for-anchor=""/>
1216   The server has fulfilled the partial GET request for the resource
1217   and the enclosed entity is a partial representation as defined in &range;.
1222<section title="Redirection 3xx" anchor="status.3xx">
1224   This class of status code indicates that further action needs to be
1225   taken by the user agent in order to fulfill the request.  The action
1226   required &MAY; be carried out by the user agent without interaction
1227   with the user if and only if the method used in the second request is
1228   GET or HEAD. A client &SHOULD; detect infinite redirection loops, since
1229   such loops generate network traffic for each redirection.
1230  <list><t>
1231      <x:h>Note:</x:h> previous versions of this specification recommended a
1232      maximum of five redirections. Content developers should be aware
1233      that there might be clients that implement such a fixed
1234      limitation.
1235  </t></list>
1238<section title="300 Multiple Choices" anchor="status.300">
1239  <iref primary="true" item="300 Multiple Choices (status code)" x:for-anchor=""/>
1240  <iref primary="true" item="Status Codes" subitem="300 Multiple Choices" x:for-anchor=""/>
1242   The requested resource corresponds to any one of a set of
1243   representations, each with its own specific location, and agent-driven
1244   negotiation information (&content-negotiation;) is being provided so that
1245   the user (or user agent) can select a preferred representation and
1246   redirect its request to that location.
1249   Unless it was a HEAD request, the response &SHOULD; include an entity
1250   containing a list of resource characteristics and location(s) from
1251   which the user or user agent can choose the one most appropriate. The
1252   entity format is specified by the media type given in the Content-Type
1253   header field. Depending upon the format and the capabilities of
1254   the user agent, selection of the most appropriate choice &MAY; be
1255   performed automatically. However, this specification does not define
1256   any standard for such automatic selection.
1259   If the server has a preferred choice of representation, it &SHOULD;
1260   include the specific URI for that representation in the Location
1261   field; user agents &MAY; use the Location field value for automatic
1262   redirection. This response is cacheable unless indicated otherwise.
1266<section title="301 Moved Permanently" anchor="status.301">
1267  <iref primary="true" item="301 Moved Permanently (status code)" x:for-anchor=""/>
1268  <iref primary="true" item="Status Codes" subitem="301 Moved Permanently" x:for-anchor=""/>
1270   The requested resource has been assigned a new permanent URI and any
1271   future references to this resource &SHOULD; use one of the returned
1272   URIs.  Clients with link editing capabilities ought to automatically
1273   re-link references to the request-target to one or more of the new
1274   references returned by the server, where possible. This response is
1275   cacheable unless indicated otherwise.
1278   The new permanent URI &SHOULD; be given by the Location field in the
1279   response. Unless the request method was HEAD, the entity of the
1280   response &SHOULD; contain a short hypertext note with a hyperlink to
1281   the new URI(s).
1284   If the 301 status code is received in response to a request method
1285   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1286   then the request &MAY; be automatically redirected by the user agent without
1287   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1288   request unless it can be confirmed by the user, since this might
1289   change the conditions under which the request was issued.
1290  <list><t>
1291      <x:h>Note:</x:h> When automatically redirecting a POST request after
1292      receiving a 301 status code, some existing HTTP/1.0 user agents
1293      will erroneously change it into a GET request.
1294  </t></list>
1298<section title="302 Found" anchor="status.302">
1299  <iref primary="true" item="302 Found (status code)" x:for-anchor=""/>
1300  <iref primary="true" item="Status Codes" subitem="302 Found" x:for-anchor=""/>
1302   The requested resource resides temporarily under a different URI.
1303   Since the redirection might be altered on occasion, the client &SHOULD;
1304   continue to use the request-target for future requests.  This response
1305   is only cacheable if indicated by a Cache-Control or Expires header
1306   field.
1309   The temporary URI &SHOULD; be given by the Location field in the
1310   response. Unless the request method was HEAD, the entity of the
1311   response &SHOULD; contain a short hypertext note with a hyperlink to
1312   the new URI(s).
1315   If the 302 status code is received in response to a request method
1316   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1317   then the request &MAY; be automatically redirected by the user agent without
1318   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1319   request unless it can be confirmed by the user, since this might
1320   change the conditions under which the request was issued.
1321  <list><t>
1322      <x:h>Note:</x:h> <xref target="RFC1945"/> and <xref target="RFC2068"/> specify that the client is not allowed
1323      to change the method on the redirected request.  However, most
1324      existing user agent implementations treat 302 as if it were a 303
1325      response, performing a GET on the Location field-value regardless
1326      of the original request method. The status codes 303 and 307 have
1327      been added for servers that wish to make unambiguously clear which
1328      kind of reaction is expected of the client.
1329  </t></list>
1333<section title="303 See Other" anchor="status.303">
1334  <iref primary="true" item="303 See Other (status code)" x:for-anchor=""/>
1335  <iref primary="true" item="Status Codes" subitem="303 See Other" x:for-anchor=""/>
1337   The server directs the user agent to a different resource, indicated
1338   by a URI in the Location header field, that provides an indirect
1339   response to the original request.  The user agent &MAY; perform a GET
1340   request on the URI in the Location field in order to obtain a
1341   representation corresponding to the response, be redirected again,
1342   or end with an error status.  The Location URI is not a substitute
1343   reference for the originally requested resource.
1346   The 303 status is generally applicable to any HTTP method.  It is
1347   primarily used to allow the output of a POST action to redirect
1348   the user agent to a selected resource, since doing so provides the
1349   information corresponding to the POST response in a form that
1350   can be separately identified, bookmarked, and cached independent
1351   of the original request.
1354   A 303 response to a GET request indicates that the requested
1355   resource does not have a representation of its own that can be
1356   transferred by the server over HTTP.  The Location URI indicates a
1357   resource that is descriptive of the requested resource such that
1358   the follow-on representation may be useful without implying that
1359   it adequately represents the previously requested resource.
1360   Note that answers to the questions of what can be represented, what
1361   representations are adequate, and what might be a useful description
1362   are outside the scope of HTTP and thus entirely determined by the
1363   resource owner(s).
1366   A 303 response &SHOULD-NOT; be cached unless it is indicated as
1367   cacheable by Cache-Control or Expires header fields.  Except for
1368   responses to a HEAD request, the entity of a 303 response &SHOULD;
1369   contain a short hypertext note with a hyperlink to the Location URI.
1373<section title="304 Not Modified" anchor="status.304">
1374  <iref primary="true" item="304 Not Modified (status code)" x:for-anchor=""/>
1375  <iref primary="true" item="Status Codes" subitem="304 Not Modified" x:for-anchor=""/>
1377   The response to the request has not been modified since the conditions
1378   indicated by the client's conditional GET request, as defined in &conditional;.
1382<section title="305 Use Proxy" anchor="status.305">
1383  <iref primary="true" item="305 Use Proxy (status code)" x:for-anchor=""/>
1384  <iref primary="true" item="Status Codes" subitem="305 Use Proxy" x:for-anchor=""/>
1386   The 305 status was defined in a previous version of this specification
1387   (see <xref target="changes.from.rfc.2616"/>), and is now deprecated.
1391<section title="306 (Unused)" anchor="status.306">
1392  <iref primary="true" item="306 (Unused) (status code)" x:for-anchor=""/>
1393  <iref primary="true" item="Status Codes" subitem="306 (Unused)" x:for-anchor=""/>
1395   The 306 status code was used in a previous version of the
1396   specification, is no longer used, and the code is reserved.
1400<section title="307 Temporary Redirect" anchor="status.307">
1401  <iref primary="true" item="307 Temporary Redirect (status code)" x:for-anchor=""/>
1402  <iref primary="true" item="Status Codes" subitem="307 Temporary Redirect" x:for-anchor=""/>
1404   The requested resource resides temporarily under a different URI.
1405   Since the redirection &MAY; be altered on occasion, the client &SHOULD;
1406   continue to use the request-target for future requests.  This response
1407   is only cacheable if indicated by a Cache-Control or Expires header
1408   field.
1411   The temporary URI &SHOULD; be given by the Location field in the
1412   response. Unless the request method was HEAD, the entity of the
1413   response &SHOULD; contain a short hypertext note with a hyperlink to
1414   the new URI(s) , since many pre-HTTP/1.1 user agents do not
1415   understand the 307 status. Therefore, the note &SHOULD; contain the
1416   information necessary for a user to repeat the original request on
1417   the new URI.
1420   If the 307 status code is received in response to a request method
1421   that is known to be "safe", as defined in <xref target="safe.methods"/>,
1422   then the request &MAY; be automatically redirected by the user agent without
1423   confirmation.  Otherwise, the user agent &MUST-NOT; automatically redirect the
1424   request unless it can be confirmed by the user, since this might
1425   change the conditions under which the request was issued.
1430<section title="Client Error 4xx" anchor="status.4xx">
1432   The 4xx class of status code is intended for cases in which the
1433   client seems to have erred. Except when responding to a HEAD request,
1434   the server &SHOULD; include an entity containing an explanation of the
1435   error situation, and whether it is a temporary or permanent
1436   condition. These status codes are applicable to any request method.
1437   User agents &SHOULD; display any included entity to the user.
1440   If the client is sending data, a server implementation using TCP
1441   &SHOULD; be careful to ensure that the client acknowledges receipt of
1442   the packet(s) containing the response, before the server closes the
1443   input connection. If the client continues sending data to the server
1444   after the close, the server's TCP stack will send a reset packet to
1445   the client, which may erase the client's unacknowledged input buffers
1446   before they can be read and interpreted by the HTTP application.
1449<section title="400 Bad Request" anchor="status.400">
1450  <iref primary="true" item="400 Bad Request (status code)" x:for-anchor=""/>
1451  <iref primary="true" item="Status Codes" subitem="400 Bad Request" x:for-anchor=""/>
1453   The request could not be understood by the server due to malformed
1454   syntax. The client &SHOULD-NOT;  repeat the request without
1455   modifications.
1459<section title="401 Unauthorized" anchor="status.401">
1460  <iref primary="true" item="401 Unauthorized (status code)" x:for-anchor=""/>
1461  <iref primary="true" item="Status Codes" subitem="401 Unauthorized" x:for-anchor=""/>
1463   The request requires user authentication (see &auth;).
1467<section title="402 Payment Required" anchor="status.402">
1468  <iref primary="true" item="402 Payment Required (status code)" x:for-anchor=""/>
1469  <iref primary="true" item="Status Codes" subitem="402 Payment Required" x:for-anchor=""/>
1471   This code is reserved for future use.
1475<section title="403 Forbidden" anchor="status.403">
1476  <iref primary="true" item="403 Forbidden (status code)" x:for-anchor=""/>
1477  <iref primary="true" item="Status Codes" subitem="403 Forbidden" x:for-anchor=""/>
1479   The server understood the request, but is refusing to fulfill it.
1480   Authorization will not help and the request &SHOULD-NOT;  be repeated.
1481   If the request method was not HEAD and the server wishes to make
1482   public why the request has not been fulfilled, it &SHOULD; describe the
1483   reason for the refusal in the entity.  If the server does not wish to
1484   make this information available to the client, the status code 404
1485   (Not Found) can be used instead.
1489<section title="404 Not Found" anchor="status.404">
1490  <iref primary="true" item="404 Not Found (status code)" x:for-anchor=""/>
1491  <iref primary="true" item="Status Codes" subitem="404 Not Found" x:for-anchor=""/>
1493   The server has not found anything matching the request-target. No
1494   indication is given of whether the condition is temporary or
1495   permanent. The 410 (Gone) status code &SHOULD; be used if the server
1496   knows, through some internally configurable mechanism, that an old
1497   resource is permanently unavailable and has no forwarding address.
1498   This status code is commonly used when the server does not wish to
1499   reveal exactly why the request has been refused, or when no other
1500   response is applicable.
1504<section title="405 Method Not Allowed" anchor="status.405">
1505  <iref primary="true" item="405 Method Not Allowed (status code)" x:for-anchor=""/>
1506  <iref primary="true" item="Status Codes" subitem="405 Method Not Allowed" x:for-anchor=""/>
1508   The method specified in the Request-Line is not allowed for the
1509   resource identified by the request-target. The response &MUST; include an
1510   Allow header containing a list of valid methods for the requested
1511   resource.
1515<section title="406 Not Acceptable" anchor="status.406">
1516  <iref primary="true" item="406 Not Acceptable (status code)" x:for-anchor=""/>
1517  <iref primary="true" item="Status Codes" subitem="406 Not Acceptable" x:for-anchor=""/>
1519   The resource identified by the request is only capable of generating
1520   response entities which have content characteristics not acceptable
1521   according to the accept headers sent in the request.
1524   Unless it was a HEAD request, the response &SHOULD; include an entity
1525   containing a list of available entity characteristics and location(s)
1526   from which the user or user agent can choose the one most
1527   appropriate. The entity format is specified by the media type given
1528   in the Content-Type header field. Depending upon the format and the
1529   capabilities of the user agent, selection of the most appropriate
1530   choice &MAY; be performed automatically. However, this specification
1531   does not define any standard for such automatic selection.
1532  <list><t>
1533      <x:h>Note:</x:h> HTTP/1.1 servers are allowed to return responses which are
1534      not acceptable according to the accept headers sent in the
1535      request. In some cases, this may even be preferable to sending a
1536      406 response. User agents are encouraged to inspect the headers of
1537      an incoming response to determine if it is acceptable.
1538  </t></list>
1541   If the response could be unacceptable, a user agent &SHOULD;
1542   temporarily stop receipt of more data and query the user for a
1543   decision on further actions.
1547<section title="407 Proxy Authentication Required" anchor="status.407">
1548  <iref primary="true" item="407 Proxy Authentication Required (status code)" x:for-anchor=""/>
1549  <iref primary="true" item="Status Codes" subitem="407 Proxy Authentication Required" x:for-anchor=""/>
1551   This code is similar to 401 (Unauthorized), but indicates that the
1552   client must first authenticate itself with the proxy (see &auth;).
1556<section title="408 Request Timeout" anchor="status.408">
1557  <iref primary="true" item="408 Request Timeout (status code)" x:for-anchor=""/>
1558  <iref primary="true" item="Status Codes" subitem="408 Request Timeout" x:for-anchor=""/>
1560   The client did not produce a request within the time that the server
1561   was prepared to wait. The client &MAY; repeat the request without
1562   modifications at any later time.
1566<section title="409 Conflict" anchor="status.409">
1567  <iref primary="true" item="409 Conflict (status code)" x:for-anchor=""/>
1568  <iref primary="true" item="Status Codes" subitem="409 Conflict" x:for-anchor=""/>
1570   The request could not be completed due to a conflict with the current
1571   state of the resource. This code is only allowed in situations where
1572   it is expected that the user might be able to resolve the conflict
1573   and resubmit the request. The response body &SHOULD; include enough
1574   information for the user to recognize the source of the conflict.
1575   Ideally, the response entity would include enough information for the
1576   user or user agent to fix the problem; however, that might not be
1577   possible and is not required.
1580   Conflicts are most likely to occur in response to a PUT request. For
1581   example, if versioning were being used and the entity being PUT
1582   included changes to a resource which conflict with those made by an
1583   earlier (third-party) request, the server might use the 409 response
1584   to indicate that it can't complete the request. In this case, the
1585   response entity would likely contain a list of the differences
1586   between the two versions in a format defined by the response
1587   Content-Type.
1591<section title="410 Gone" anchor="status.410">
1592  <iref primary="true" item="410 Gone (status code)" x:for-anchor=""/>
1593  <iref primary="true" item="Status Codes" subitem="410 Gone" x:for-anchor=""/>
1595   The requested resource is no longer available at the server and no
1596   forwarding address is known. This condition is expected to be
1597   considered permanent. Clients with link editing capabilities &SHOULD;
1598   delete references to the request-target after user approval. If the
1599   server does not know, or has no facility to determine, whether or not
1600   the condition is permanent, the status code 404 (Not Found) &SHOULD; be
1601   used instead. This response is cacheable unless indicated otherwise.
1604   The 410 response is primarily intended to assist the task of web
1605   maintenance by notifying the recipient that the resource is
1606   intentionally unavailable and that the server owners desire that
1607   remote links to that resource be removed. Such an event is common for
1608   limited-time, promotional services and for resources belonging to
1609   individuals no longer working at the server's site. It is not
1610   necessary to mark all permanently unavailable resources as "gone" or
1611   to keep the mark for any length of time -- that is left to the
1612   discretion of the server owner.
1616<section title="411 Length Required" anchor="status.411">
1617  <iref primary="true" item="411 Length Required (status code)" x:for-anchor=""/>
1618  <iref primary="true" item="Status Codes" subitem="411 Length Required" x:for-anchor=""/>
1620   The server refuses to accept the request without a defined Content-Length.
1621   The client &MAY; repeat the request if it adds a valid
1622   Content-Length header field containing the length of the message-body
1623   in the request message.
1627<section title="412 Precondition Failed" anchor="status.412">
1628  <iref primary="true" item="412 Precondition Failed (status code)" x:for-anchor=""/>
1629  <iref primary="true" item="Status Codes" subitem="412 Precondition Failed" x:for-anchor=""/>
1631   The precondition given in one or more of the request-header fields
1632   evaluated to false when it was tested on the server, as defined in
1633   &conditional;.
1637<section title="413 Request Entity Too Large" anchor="status.413">
1638  <iref primary="true" item="413 Request Entity Too Large (status code)" x:for-anchor=""/>
1639  <iref primary="true" item="Status Codes" subitem="413 Request Entity Too Large" x:for-anchor=""/>
1641   The server is refusing to process a request because the request
1642   entity is larger than the server is willing or able to process. The
1643   server &MAY; close the connection to prevent the client from continuing
1644   the request.
1647   If the condition is temporary, the server &SHOULD; include a Retry-After
1648   header field to indicate that it is temporary and after what
1649   time the client &MAY; try again.
1653<section title="414 Request-target Too Long" anchor="status.414">
1654  <iref primary="true" item="414 Request-target Too Long (status code)" x:for-anchor=""/>
1655  <iref primary="true" item="Status Codes" subitem="414 Request-target Too Long" x:for-anchor=""/>
1657   The server is refusing to service the request because the request-target
1658   is longer than the server is willing to interpret. This rare
1659   condition is only likely to occur when a client has improperly
1660   converted a POST request to a GET request with long query
1661   information, when the client has descended into a URI "black hole" of
1662   redirection (e.g., a redirected URI prefix that points to a suffix of
1663   itself), or when the server is under attack by a client attempting to
1664   exploit security holes present in some servers using fixed-length
1665   buffers for reading or manipulating the request-target.
1669<section title="415 Unsupported Media Type" anchor="status.415">
1670  <iref primary="true" item="415 Unsupported Media Type (status code)" x:for-anchor=""/>
1671  <iref primary="true" item="Status Codes" subitem="415 Unsupported Media Type" x:for-anchor=""/>
1673   The server is refusing to service the request because the entity of
1674   the request is in a format not supported by the requested resource
1675   for the requested method.
1679<section title="416 Requested Range Not Satisfiable" anchor="status.416">
1680  <iref primary="true" item="416 Requested Range Not Satisfiable (status code)" x:for-anchor=""/>
1681  <iref primary="true" item="Status Codes" subitem="416 Requested Range Not Satisfiable" x:for-anchor=""/>
1683   The request included a Range request-header field (&header-range;) and none of
1684   the range-specifier values in this field overlap the current extent
1685   of the selected resource.
1689<section title="417 Expectation Failed" anchor="status.417">
1690  <iref primary="true" item="417 Expectation Failed (status code)" x:for-anchor=""/>
1691  <iref primary="true" item="Status Codes" subitem="417 Expectation Failed" x:for-anchor=""/>
1693   The expectation given in an Expect request-header field (see <xref target="header.expect"/>)
1694   could not be met by this server, or, if the server is a proxy,
1695   the server has unambiguous evidence that the request could not be met
1696   by the next-hop server.
1701<section title="Server Error 5xx" anchor="status.5xx">
1703   Response status codes beginning with the digit "5" indicate cases in
1704   which the server is aware that it has erred or is incapable of
1705   performing the request. Except when responding to a HEAD request, the
1706   server &SHOULD; include an entity containing an explanation of the
1707   error situation, and whether it is a temporary or permanent
1708   condition. User agents &SHOULD; display any included entity to the
1709   user. These response codes are applicable to any request method.
1712<section title="500 Internal Server Error" anchor="status.500">
1713  <iref primary="true" item="500 Internal Server Error (status code)" x:for-anchor=""/>
1714  <iref primary="true" item="Status Codes" subitem="500 Internal Server Error" x:for-anchor=""/>
1716   The server encountered an unexpected condition which prevented it
1717   from fulfilling the request.
1721<section title="501 Not Implemented" anchor="status.501">
1722  <iref primary="true" item="501 Not Implemented (status code)" x:for-anchor=""/>
1723  <iref primary="true" item="Status Codes" subitem="501 Not Implemented" x:for-anchor=""/>
1725   The server does not support the functionality required to fulfill the
1726   request. This is the appropriate response when the server does not
1727   recognize the request method and is not capable of supporting it for
1728   any resource.
1732<section title="502 Bad Gateway" anchor="status.502">
1733  <iref primary="true" item="502 Bad Gateway (status code)" x:for-anchor=""/>
1734  <iref primary="true" item="Status Codes" subitem="502 Bad Gateway" x:for-anchor=""/>
1736   The server, while acting as a gateway or proxy, received an invalid
1737   response from the upstream server it accessed in attempting to
1738   fulfill the request.
1742<section title="503 Service Unavailable" anchor="status.503">
1743  <iref primary="true" item="503 Service Unavailable (status code)" x:for-anchor=""/>
1744  <iref primary="true" item="Status Codes" subitem="503 Service Unavailable" x:for-anchor=""/>
1746   The server is currently unable to handle the request due to a
1747   temporary overloading or maintenance of the server. The implication
1748   is that this is a temporary condition which will be alleviated after
1749   some delay. If known, the length of the delay &MAY; be indicated in a
1750   Retry-After header. If no Retry-After is given, the client &SHOULD;
1751   handle the response as it would for a 500 response.
1752  <list><t>
1753      <x:h>Note:</x:h> The existence of the 503 status code does not imply that a
1754      server must use it when becoming overloaded. Some servers may wish
1755      to simply refuse the connection.
1756  </t></list>
1760<section title="504 Gateway Timeout" anchor="status.504">
1761  <iref primary="true" item="504 Gateway Timeout (status code)" x:for-anchor=""/>
1762  <iref primary="true" item="Status Codes" subitem="504 Gateway Timeout" x:for-anchor=""/>
1764   The server, while acting as a gateway or proxy, did not receive a
1765   timely response from the upstream server specified by the URI (e.g.
1766   HTTP, FTP, LDAP) or some other auxiliary server (e.g. DNS) it needed
1767   to access in attempting to complete the request.
1768  <list><t>
1769      <x:h>Note:</x:h> Note to implementors: some deployed proxies are known to
1770      return 400 or 500 when DNS lookups time out.
1771  </t></list>
1775<section title="505 HTTP Version Not Supported" anchor="status.505">
1776  <iref primary="true" item="505 HTTP Version Not Supported (status code)" x:for-anchor=""/>
1777  <iref primary="true" item="Status Codes" subitem="505 HTTP Version Not Supported" x:for-anchor=""/>
1779   The server does not support, or refuses to support, the protocol
1780   version that was used in the request message. The server is
1781   indicating that it is unable or unwilling to complete the request
1782   using the same major version as the client, as described in &http-version;,
1783   other than with this error message. The response &SHOULD; contain
1784   an entity describing why that version is not supported and what other
1785   protocols are supported by that server.
1793<section title="Header Field Definitions" anchor="header.fields">
1795   This section defines the syntax and semantics of HTTP/1.1 header fields
1796   related to request and response semantics.
1799   For entity-header fields, both sender and recipient refer to either the
1800   client or the server, depending on who sends and who receives the entity.
1803<section title="Allow" anchor="header.allow">
1804  <iref primary="true" item="Allow header" x:for-anchor=""/>
1805  <iref primary="true" item="Headers" subitem="Allow" x:for-anchor=""/>
1806  <x:anchor-alias value="Allow"/>
1807  <x:anchor-alias value="Allow-v"/>
1809      The response-header field "Allow" lists the set of methods advertised as
1810      supported by the resource identified by the request-target. The purpose of
1811      this field is strictly to inform the recipient of valid methods
1812      associated with the resource. An Allow header field &MUST; be
1813      present in a 405 (Method Not Allowed) response.
1815<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Allow"/><iref primary="true" item="Grammar" subitem="Allow-v"/>
1816  <x:ref>Allow</x:ref>   = "Allow" ":" <x:ref>OWS</x:ref> <x:ref>Allow-v</x:ref>
1817  <x:ref>Allow-v</x:ref> = #<x:ref>Method</x:ref>
1820      Example of use:
1822<figure><artwork type="example">
1823  Allow: GET, HEAD, PUT
1826      The actual set of allowed methods is defined
1827      by the origin server at the time of each request.
1830      A proxy &MUST-NOT; modify the Allow header field even if it does not
1831      understand all the methods specified, since the user agent might
1832      have other means of communicating with the origin server.
1836<section title="Expect" anchor="header.expect">
1837  <iref primary="true" item="Expect header" x:for-anchor=""/>
1838  <iref primary="true" item="Headers" subitem="Expect" x:for-anchor=""/>
1839  <x:anchor-alias value="Expect"/>
1840  <x:anchor-alias value="Expect-v"/>
1841  <x:anchor-alias value="expectation"/>
1842  <x:anchor-alias value="expectation-extension"/>
1843  <x:anchor-alias value="expect-params"/>
1845   The request-header field "Expect" is used to indicate that particular
1846   server behaviors are required by the client.
1848<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Expect"/><iref primary="true" item="Grammar" subitem="Expect-v"/><iref primary="true" item="Grammar" subitem="expectation"/><iref primary="true" item="Grammar" subitem="expectation-extension"/><iref primary="true" item="Grammar" subitem="expect-params"/>
1849  <x:ref>Expect</x:ref>       = "Expect" ":" <x:ref>OWS</x:ref> <x:ref>Expect-v</x:ref>
1850  <x:ref>Expect-v</x:ref>     = 1#<x:ref>expectation</x:ref>
1852  <x:ref>expectation</x:ref>  = "100-continue" / <x:ref>expectation-extension</x:ref>
1853  <x:ref>expectation-extension</x:ref> = <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> )
1854                           *<x:ref>expect-params</x:ref> ]
1855  <x:ref>expect-params</x:ref> = ";" <x:ref>token</x:ref> [ "=" ( <x:ref>token</x:ref> / <x:ref>quoted-string</x:ref> ) ]
1858   A server that does not understand or is unable to comply with any of
1859   the expectation values in the Expect field of a request &MUST; respond
1860   with appropriate error status. The server &MUST; respond with a 417
1861   (Expectation Failed) status if any of the expectations cannot be met
1862   or, if there are other problems with the request, some other 4xx
1863   status.
1866   This header field is defined with extensible syntax to allow for
1867   future extensions. If a server receives a request containing an
1868   Expect field that includes an expectation-extension that it does not
1869   support, it &MUST; respond with a 417 (Expectation Failed) status.
1872   Comparison of expectation values is case-insensitive for unquoted
1873   tokens (including the 100-continue token), and is case-sensitive for
1874   quoted-string expectation-extensions.
1877   The Expect mechanism is hop-by-hop: that is, an HTTP/1.1 proxy &MUST;
1878   return a 417 (Expectation Failed) status if it receives a request
1879   with an expectation that it cannot meet. However, the Expect
1880   request-header itself is end-to-end; it &MUST; be forwarded if the
1881   request is forwarded.
1884   Many older HTTP/1.0 and HTTP/1.1 applications do not understand the
1885   Expect header.
1888   See &use100; for the use of the 100 (Continue) status.
1892<section title="From" anchor="header.from">
1893  <iref primary="true" item="From header" x:for-anchor=""/>
1894  <iref primary="true" item="Headers" subitem="From" x:for-anchor=""/>
1895  <x:anchor-alias value="From"/>
1896  <x:anchor-alias value="From-v"/>
1897  <x:anchor-alias value="mailbox"/>
1899   The request-header field "From", if given, &SHOULD; contain an Internet
1900   e-mail address for the human user who controls the requesting user
1901   agent. The address &SHOULD; be machine-usable, as defined by "mailbox"
1902   in <xref x:sec="3.4" x:fmt="of" target="RFC5322"/>:
1904<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="From"/><iref primary="true" item="Grammar" subitem="From-v"/>
1905  <x:ref>From</x:ref>    = "From" ":" <x:ref>OWS</x:ref> <x:ref>From-v</x:ref>
1906  <x:ref>From-v</x:ref>  = <x:ref>mailbox</x:ref>
1908  <x:ref>mailbox</x:ref> = &lt;mailbox, defined in <xref x:sec="3.4" x:fmt="," target="RFC5322"/>&gt;
1911   An example is:
1913<figure><artwork type="example">
1914  From:
1917   This header field &MAY; be used for logging purposes and as a means for
1918   identifying the source of invalid or unwanted requests. It &SHOULD-NOT;
1919   be used as an insecure form of access protection. The interpretation
1920   of this field is that the request is being performed on behalf of the
1921   person given, who accepts responsibility for the method performed. In
1922   particular, robot agents &SHOULD; include this header so that the
1923   person responsible for running the robot can be contacted if problems
1924   occur on the receiving end.
1927   The Internet e-mail address in this field &MAY; be separate from the
1928   Internet host which issued the request. For example, when a request
1929   is passed through a proxy the original issuer's address &SHOULD; be
1930   used.
1933   The client &SHOULD-NOT;  send the From header field without the user's
1934   approval, as it might conflict with the user's privacy interests or
1935   their site's security policy. It is strongly recommended that the
1936   user be able to disable, enable, and modify the value of this field
1937   at any time prior to a request.
1941<section title="Location" anchor="header.location">
1942  <iref primary="true" item="Location header" x:for-anchor=""/>
1943  <iref primary="true" item="Headers" subitem="Location" x:for-anchor=""/>
1944  <x:anchor-alias value="Location"/>
1945  <x:anchor-alias value="Location-v"/>
1947   The response-header field "Location" is used for the identification of a
1948   new resource or to redirect the recipient to a location other than the
1949   request-target for completion of the request.  For 201 (Created)
1950   responses, the Location is that of the new resource which was created
1951   by the request. For 3xx responses, the location &SHOULD; indicate the
1952   server's preferred URI for automatic redirection to the resource. The
1953   field value consists of a single absolute URI.
1955<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Location"/><iref primary="true" item="Grammar" subitem="Location-v"/>
1956  <x:ref>Location</x:ref>       = "Location" ":" <x:ref>OWS</x:ref> <x:ref>Location-v</x:ref>
1957  <x:ref>Location-v</x:ref>     = <x:ref>absolute-URI</x:ref> [ "#" <x:ref>fragment</x:ref> ]
1960   An example is:
1962<figure><artwork type="example">
1963  Location:
1966  <list><t>
1967      <x:h>Note:</x:h> The Content-Location header field (&header-content-location;) differs
1968      from Location in that the Content-Location identifies the original
1969      location of the entity enclosed in the response. It is therefore
1970      possible for a response to contain header fields for both Location
1971      and Content-Location.
1972  </t></list>
1975   There are circumstances in which a fragment identifier in a Location URL would not be appropriate:
1976   <list style="symbols">
1977      <t>With a 201 Created response, because in this usage the Location header specifies the URL for the entire created resource.</t>
1978      <t>With a 300 Multiple Choices, since the choice decision is intended to be made on resource characteristics and not fragment characteristics.</t>
1979      <t>With 305 Use Proxy.</t>
1980   </list>
1984<section title="Max-Forwards" anchor="header.max-forwards">
1985  <iref primary="true" item="Max-Forwards header" x:for-anchor=""/>
1986  <iref primary="true" item="Headers" subitem="Max-Forwards" x:for-anchor=""/>
1987  <x:anchor-alias value="Max-Forwards"/>
1988  <x:anchor-alias value="Max-Forwards-v"/>
1990   The request-header "Max-Forwards" field provides a mechanism with the
1991   TRACE (<xref target="TRACE"/>) and OPTIONS (<xref target="OPTIONS"/>) methods to limit the
1992   number of proxies or gateways that can forward the request to the
1993   next inbound server. This can be useful when the client is attempting
1994   to trace a request chain which appears to be failing or looping in
1995   mid-chain.
1997<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Max-Forwards"/><iref primary="true" item="Grammar" subitem="Max-Forwards-v"/>
1998  <x:ref>Max-Forwards</x:ref>   = "Max-Forwards" ":" <x:ref>OWS</x:ref> <x:ref>Max-Forwards-v</x:ref>
1999  <x:ref>Max-Forwards-v</x:ref> = 1*<x:ref>DIGIT</x:ref>
2002   The Max-Forwards value is a decimal integer indicating the remaining
2003   number of times this request message may be forwarded.
2006   Each proxy or gateway recipient of a TRACE or OPTIONS request
2007   containing a Max-Forwards header field &MUST; check and update its
2008   value prior to forwarding the request. If the received value is zero
2009   (0), the recipient &MUST-NOT; forward the request; instead, it &MUST;
2010   respond as the final recipient. If the received Max-Forwards value is
2011   greater than zero, then the forwarded message &MUST; contain an updated
2012   Max-Forwards field with a value decremented by one (1).
2015   The Max-Forwards header field &MAY; be ignored for all other methods
2016   defined by this specification and for any extension methods for which
2017   it is not explicitly referred to as part of that method definition.
2021<section title="Referer" anchor="header.referer">
2022  <iref primary="true" item="Referer header" x:for-anchor=""/>
2023  <iref primary="true" item="Headers" subitem="Referer" x:for-anchor=""/>
2024  <x:anchor-alias value="Referer"/>
2025  <x:anchor-alias value="Referer-v"/>
2027   The request-header field "Referer" [sic] allows the client to specify,
2028   for the server's benefit, the address (URI) of the resource from
2029   which the request-target was obtained (the "referrer", although the
2030   header field is misspelled.) The Referer request-header allows a
2031   server to generate lists of back-links to resources for interest,
2032   logging, optimized caching, etc. It also allows obsolete or mistyped
2033   links to be traced for maintenance. The Referer field &MUST-NOT; be
2034   sent if the request-target was obtained from a source that does not have
2035   its own URI, such as input from the user keyboard.
2037<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Referer"/><iref primary="true" item="Grammar" subitem="Referer-v"/>
2038  <x:ref>Referer</x:ref>        = "Referer" ":" <x:ref>OWS</x:ref> <x:ref>Referer-v</x:ref>
2039  <x:ref>Referer-v</x:ref>      = <x:ref>absolute-URI</x:ref> / <x:ref>partial-URI</x:ref>
2042   Example:
2044<figure><artwork type="example">
2045  Referer:
2048   If the field value is a relative URI, it &SHOULD; be interpreted
2049   relative to the request-target. The URI &MUST-NOT; include a fragment. See
2050   <xref target=""/> for security considerations.
2054<section title="Retry-After" anchor="header.retry-after">
2055  <iref primary="true" item="Retry-After header" x:for-anchor=""/>
2056  <iref primary="true" item="Headers" subitem="Retry-After" x:for-anchor=""/>
2057  <x:anchor-alias value="Retry-After"/>
2058  <x:anchor-alias value="Retry-After-v"/>
2060   The response-header "Retry-After" field can be used with a 503 (Service
2061   Unavailable) response to indicate how long the service is expected to
2062   be unavailable to the requesting client. This field &MAY; also be used
2063   with any 3xx (Redirection) response to indicate the minimum time the
2064   user-agent is asked wait before issuing the redirected request. The
2065   value of this field can be either an HTTP-date or an integer number
2066   of seconds (in decimal) after the time of the response.
2068<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Retry-After"/><iref primary="true" item="Grammar" subitem="Retry-After-v"/>
2069  <x:ref>Retry-After</x:ref>   = "Retry-After" ":" <x:ref>OWS</x:ref> <x:ref>Retry-After-v</x:ref>
2070  <x:ref>Retry-After-v</x:ref> = <x:ref>HTTP-date</x:ref> / <x:ref>delta-seconds</x:ref>
2072<t anchor="">
2073  <x:anchor-alias value="delta-seconds"/>
2074   Time spans are non-negative decimal integers, representing time in
2075   seconds.
2077<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="delta-seconds"/>
2078  <x:ref>delta-seconds</x:ref>  = 1*<x:ref>DIGIT</x:ref>
2081   Two examples of its use are
2083<figure><artwork type="example">
2084  Retry-After: Fri, 31 Dec 1999 23:59:59 GMT
2085  Retry-After: 120
2088   In the latter example, the delay is 2 minutes.
2092<section title="Server" anchor="header.server">
2093  <iref primary="true" item="Server header" x:for-anchor=""/>
2094  <iref primary="true" item="Headers" subitem="Server" x:for-anchor=""/>
2095  <x:anchor-alias value="Server"/>
2096  <x:anchor-alias value="Server-v"/>
2098   The response-header field "Server" contains information about the
2099   software used by the origin server to handle the request. The field
2100   can contain multiple product tokens (&product-tokens;) and comments
2101   identifying the server and any significant subproducts. The product
2102   tokens are listed in order of their significance for identifying the
2103   application.
2105<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Server"/><iref primary="true" item="Grammar" subitem="Server-v"/>
2106  <x:ref>Server</x:ref>         = "Server" ":" <x:ref>OWS</x:ref> <x:ref>Server-v</x:ref>
2107  <x:ref>Server-v</x:ref>       = <x:ref>product</x:ref>
2108                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2111   Example:
2113<figure><artwork type="example">
2114  Server: CERN/3.0 libwww/2.17
2117   If the response is being forwarded through a proxy, the proxy
2118   application &MUST-NOT; modify the Server response-header. Instead, it
2119   &MUST; include a Via field (as described in &header-via;).
2120  <list><t>
2121      <x:h>Note:</x:h> Revealing the specific software version of the server might
2122      allow the server machine to become more vulnerable to attacks
2123      against software that is known to contain security holes. Server
2124      implementors are encouraged to make this field a configurable
2125      option.
2126  </t></list>
2130<section title="User-Agent" anchor="header.user-agent">
2131  <iref primary="true" item="User-Agent header" x:for-anchor=""/>
2132  <iref primary="true" item="Headers" subitem="User-Agent" x:for-anchor=""/>
2133  <x:anchor-alias value="User-Agent"/>
2134  <x:anchor-alias value="User-Agent-v"/>
2136   The request-header field "User-Agent" contains information about the
2137   user agent originating the request. This is for statistical purposes,
2138   the tracing of protocol violations, and automated recognition of user
2139   agents for the sake of tailoring responses to avoid particular user
2140   agent limitations. User agents &SHOULD; include this field with
2141   requests. The field can contain multiple product tokens (&product-tokens;)
2142   and comments identifying the agent and any subproducts which form a
2143   significant part of the user agent. By convention, the product tokens
2144   are listed in order of their significance for identifying the
2145   application.
2147<figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="User-Agent"/><iref primary="true" item="Grammar" subitem="User-Agent-v"/>
2148  <x:ref>User-Agent</x:ref>     = "User-Agent" ":" <x:ref>OWS</x:ref> <x:ref>User-Agent-v</x:ref>
2149  <x:ref>User-Agent-v</x:ref>   = <x:ref>product</x:ref>
2150                   *( <x:ref>RWS</x:ref> ( <x:ref>product</x:ref> / <x:ref>comment</x:ref> ) )
2153   Example:
2155<figure><artwork type="example">
2156  User-Agent: CERN-LineMode/2.15 libwww/2.17b3
2162<section title="IANA Considerations" anchor="IANA.considerations">
2164<section title="Method Registry" anchor="method.registration">
2166  The registration procedure for HTTP Methods is defined by
2167  <xref target="method.registry"/> of this document.
2170   The HTTP Method Registry located at <eref target=""/>
2171   should be populated with the registrations below:
2173<!--AUTOGENERATED FROM extract-method-defs.xslt, do not edit manually-->
2174<texttable align="left" suppress-title="true" anchor="iana.method.registration.table">
2175   <ttcol>Method</ttcol>
2176   <ttcol>Safe</ttcol>
2177   <ttcol>Reference</ttcol>
2178   <c>CONNECT</c>
2179   <c>no</c>
2180   <c>
2181      <xref target="CONNECT"/>
2182   </c>
2183   <c>DELETE</c>
2184   <c>no</c>
2185   <c>
2186      <xref target="DELETE"/>
2187   </c>
2188   <c>GET</c>
2189   <c>yes</c>
2190   <c>
2191      <xref target="GET"/>
2192   </c>
2193   <c>HEAD</c>
2194   <c>yes</c>
2195   <c>
2196      <xref target="HEAD"/>
2197   </c>
2198   <c>OPTIONS</c>
2199   <c>yes</c>
2200   <c>
2201      <xref target="OPTIONS"/>
2202   </c>
2203   <c>POST</c>
2204   <c>no</c>
2205   <c>
2206      <xref target="POST"/>
2207   </c>
2208   <c>PUT</c>
2209   <c>no</c>
2210   <c>
2211      <xref target="PUT"/>
2212   </c>
2213   <c>TRACE</c>
2214   <c>yes</c>
2215   <c>
2216      <xref target="TRACE"/>
2217   </c>
2222<section title="Status Code Registry" anchor="status.code.registration">
2224   The registration procedure for HTTP Status Codes -- previously defined
2225   in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/> -- is now defined
2226   by <xref target="status.code.registry"/> of this document.
2229   The HTTP Status Code Registry located at <eref target=""/>
2230   should be updated with the registrations below:
2232<!--AUTOGENERATED FROM extract-status-code-defs.xslt, do not edit manually-->
2233<texttable align="left" suppress-title="true" anchor="iana.status.code.registration.table">
2234   <ttcol>Value</ttcol>
2235   <ttcol>Description</ttcol>
2236   <ttcol>Reference</ttcol>
2237   <c>100</c>
2238   <c>Continue</c>
2239   <c>
2240      <xref target="status.100"/>
2241   </c>
2242   <c>101</c>
2243   <c>Switching Protocols</c>
2244   <c>
2245      <xref target="status.101"/>
2246   </c>
2247   <c>200</c>
2248   <c>OK</c>
2249   <c>
2250      <xref target="status.200"/>
2251   </c>
2252   <c>201</c>
2253   <c>Created</c>
2254   <c>
2255      <xref target="status.201"/>
2256   </c>
2257   <c>202</c>
2258   <c>Accepted</c>
2259   <c>
2260      <xref target="status.202"/>
2261   </c>
2262   <c>203</c>
2263   <c>Non-Authoritative Information</c>
2264   <c>
2265      <xref target="status.203"/>
2266   </c>
2267   <c>204</c>
2268   <c>No Content</c>
2269   <c>
2270      <xref target="status.204"/>
2271   </c>
2272   <c>205</c>
2273   <c>Reset Content</c>
2274   <c>
2275      <xref target="status.205"/>
2276   </c>
2277   <c>206</c>
2278   <c>Partial Content</c>
2279   <c>
2280      <xref target="status.206"/>
2281   </c>
2282   <c>300</c>
2283   <c>Multiple Choices</c>
2284   <c>
2285      <xref target="status.300"/>
2286   </c>
2287   <c>301</c>
2288   <c>Moved Permanently</c>
2289   <c>
2290      <xref target="status.301"/>
2291   </c>
2292   <c>302</c>
2293   <c>Found</c>
2294   <c>
2295      <xref target="status.302"/>
2296   </c>
2297   <c>303</c>
2298   <c>See Other</c>
2299   <c>
2300      <xref target="status.303"/>
2301   </c>
2302   <c>304</c>
2303   <c>Not Modified</c>
2304   <c>
2305      <xref target="status.304"/>
2306   </c>
2307   <c>305</c>
2308   <c>Use Proxy</c>
2309   <c>
2310      <xref target="status.305"/>
2311   </c>
2312   <c>306</c>
2313   <c>(Unused)</c>
2314   <c>
2315      <xref target="status.306"/>
2316   </c>
2317   <c>307</c>
2318   <c>Temporary Redirect</c>
2319   <c>
2320      <xref target="status.307"/>
2321   </c>
2322   <c>400</c>
2323   <c>Bad Request</c>
2324   <c>
2325      <xref target="status.400"/>
2326   </c>
2327   <c>401</c>
2328   <c>Unauthorized</c>
2329   <c>
2330      <xref target="status.401"/>
2331   </c>
2332   <c>402</c>
2333   <c>Payment Required</c>
2334   <c>
2335      <xref target="status.402"/>
2336   </c>
2337   <c>403</c>
2338   <c>Forbidden</c>
2339   <c>
2340      <xref target="status.403"/>
2341   </c>
2342   <c>404</c>
2343   <c>Not Found</c>
2344   <c>
2345      <xref target="status.404"/>
2346   </c>
2347   <c>405</c>
2348   <c>Method Not Allowed</c>
2349   <c>
2350      <xref target="status.405"/>
2351   </c>
2352   <c>406</c>
2353   <c>Not Acceptable</c>
2354   <c>
2355      <xref target="status.406"/>
2356   </c>
2357   <c>407</c>
2358   <c>Proxy Authentication Required</c>
2359   <c>
2360      <xref target="status.407"/>
2361   </c>
2362   <c>408</c>
2363   <c>Request Timeout</c>
2364   <c>
2365      <xref target="status.408"/>
2366   </c>
2367   <c>409</c>
2368   <c>Conflict</c>
2369   <c>
2370      <xref target="status.409"/>
2371   </c>
2372   <c>410</c>
2373   <c>Gone</c>
2374   <c>
2375      <xref target="status.410"/>
2376   </c>
2377   <c>411</c>
2378   <c>Length Required</c>
2379   <c>
2380      <xref target="status.411"/>
2381   </c>
2382   <c>412</c>
2383   <c>Precondition Failed</c>
2384   <c>
2385      <xref target="status.412"/>
2386   </c>
2387   <c>413</c>
2388   <c>Request Entity Too Large</c>
2389   <c>
2390      <xref target="status.413"/>
2391   </c>
2392   <c>414</c>
2393   <c>Request-target Too Long</c>
2394   <c>
2395      <xref target="status.414"/>
2396   </c>
2397   <c>415</c>
2398   <c>Unsupported Media Type</c>
2399   <c>
2400      <xref target="status.415"/>
2401   </c>
2402   <c>416</c>
2403   <c>Requested Range Not Satisfiable</c>
2404   <c>
2405      <xref target="status.416"/>
2406   </c>
2407   <c>417</c>
2408   <c>Expectation Failed</c>
2409   <c>
2410      <xref target="status.417"/>
2411   </c>
2412   <c>500</c>
2413   <c>Internal Server Error</c>
2414   <c>
2415      <xref target="status.500"/>
2416   </c>
2417   <c>501</c>
2418   <c>Not Implemented</c>
2419   <c>
2420      <xref target="status.501"/>
2421   </c>
2422   <c>502</c>
2423   <c>Bad Gateway</c>
2424   <c>
2425      <xref target="status.502"/>
2426   </c>
2427   <c>503</c>
2428   <c>Service Unavailable</c>
2429   <c>
2430      <xref target="status.503"/>
2431   </c>
2432   <c>504</c>
2433   <c>Gateway Timeout</c>
2434   <c>
2435      <xref target="status.504"/>
2436   </c>
2437   <c>505</c>
2438   <c>HTTP Version Not Supported</c>
2439   <c>
2440      <xref target="status.505"/>
2441   </c>
2445<section title="Message Header Registration" anchor="message.header.registration">
2447   The Message Header Registry located at <eref target=""/> should be updated
2448   with the permanent registrations below (see <xref target="RFC3864"/>):
2450<!--AUTOGENERATED FROM extract-header-defs.xslt, do not edit manually-->
2451<texttable align="left" suppress-title="true" anchor="iana.header.registration.table">
2452   <ttcol>Header Field Name</ttcol>
2453   <ttcol>Protocol</ttcol>
2454   <ttcol>Status</ttcol>
2455   <ttcol>Reference</ttcol>
2456   <c>Allow</c>
2457   <c>http</c>
2458   <c>standard</c>
2459   <c>
2460      <xref target="header.allow"/>
2461   </c>
2462   <c>Expect</c>
2463   <c>http</c>
2464   <c>standard</c>
2465   <c>
2466      <xref target="header.expect"/>
2467   </c>
2468   <c>From</c>
2469   <c>http</c>
2470   <c>standard</c>
2471   <c>
2472      <xref target="header.from"/>
2473   </c>
2474   <c>Location</c>
2475   <c>http</c>
2476   <c>standard</c>
2477   <c>
2478      <xref target="header.location"/>
2479   </c>
2480   <c>Max-Forwards</c>
2481   <c>http</c>
2482   <c>standard</c>
2483   <c>
2484      <xref target="header.max-forwards"/>
2485   </c>
2486   <c>Referer</c>
2487   <c>http</c>
2488   <c>standard</c>
2489   <c>
2490      <xref target="header.referer"/>
2491   </c>
2492   <c>Retry-After</c>
2493   <c>http</c>
2494   <c>standard</c>
2495   <c>
2496      <xref target="header.retry-after"/>
2497   </c>
2498   <c>Server</c>
2499   <c>http</c>
2500   <c>standard</c>
2501   <c>
2502      <xref target="header.server"/>
2503   </c>
2504   <c>User-Agent</c>
2505   <c>http</c>
2506   <c>standard</c>
2507   <c>
2508      <xref target="header.user-agent"/>
2509   </c>
2513   The change controller is: "IETF ( - Internet Engineering Task Force".
2518<section title="Security Considerations" anchor="security.considerations">
2520   This section is meant to inform application developers, information
2521   providers, and users of the security limitations in HTTP/1.1 as
2522   described by this document. The discussion does not include
2523   definitive solutions to the problems revealed, though it does make
2524   some suggestions for reducing security risks.
2527<section title="Transfer of Sensitive Information" anchor="security.sensitive">
2529   Like any generic data transfer protocol, HTTP cannot regulate the
2530   content of the data that is transferred, nor is there any a priori
2531   method of determining the sensitivity of any particular piece of
2532   information within the context of any given request. Therefore,
2533   applications &SHOULD; supply as much control over this information as
2534   possible to the provider of that information. Four header fields are
2535   worth special mention in this context: Server, Via, Referer and From.
2538   Revealing the specific software version of the server might allow the
2539   server machine to become more vulnerable to attacks against software
2540   that is known to contain security holes. Implementors &SHOULD; make the
2541   Server header field a configurable option.
2544   Proxies which serve as a portal through a network firewall &SHOULD;
2545   take special precautions regarding the transfer of header information
2546   that identifies the hosts behind the firewall. In particular, they
2547   &SHOULD; remove, or replace with sanitized versions, any Via fields
2548   generated behind the firewall.
2551   The Referer header allows reading patterns to be studied and reverse
2552   links drawn. Although it can be very useful, its power can be abused
2553   if user details are not separated from the information contained in
2554   the Referer. Even when the personal information has been removed, the
2555   Referer header might indicate a private document's URI whose
2556   publication would be inappropriate.
2559   The information sent in the From field might conflict with the user's
2560   privacy interests or their site's security policy, and hence it
2561   &SHOULD-NOT;  be transmitted without the user being able to disable,
2562   enable, and modify the contents of the field. The user &MUST; be able
2563   to set the contents of this field within a user preference or
2564   application defaults configuration.
2567   We suggest, though do not require, that a convenient toggle interface
2568   be provided for the user to enable or disable the sending of From and
2569   Referer information.
2572   The User-Agent (<xref target="header.user-agent"/>) or Server (<xref target="header.server"/>) header
2573   fields can sometimes be used to determine that a specific client or
2574   server have a particular security hole which might be exploited.
2575   Unfortunately, this same information is often used for other valuable
2576   purposes for which HTTP currently has no better mechanism.
2580<section title="Encoding Sensitive Information in URIs" anchor="">
2582   Because the source of a link might be private information or might
2583   reveal an otherwise private information source, it is strongly
2584   recommended that the user be able to select whether or not the
2585   Referer field is sent. For example, a browser client could have a
2586   toggle switch for browsing openly/anonymously, which would
2587   respectively enable/disable the sending of Referer and From
2588   information.
2591   Clients &SHOULD-NOT; include a Referer header field in a (non-secure)
2592   HTTP request if the referring page was transferred with a secure
2593   protocol.
2596   Authors of services should not use
2597   GET-based forms for the submission of sensitive data because that
2598   data will be encoded in the Request-target. Many existing
2599   servers, proxies, and user agents log or display the Request-target in
2600   places where it might be visible to third parties. Such services can
2601   use POST-based form submission instead.
2605<section title="Location Headers and Spoofing" anchor="location.spoofing">
2607   If a single server supports multiple organizations that do not trust
2608   one another, then it &MUST; check the values of Location and Content-Location
2609   headers in responses that are generated under control of
2610   said organizations to make sure that they do not attempt to
2611   invalidate resources over which they have no authority.
2617<section title="Acknowledgments" anchor="ack">
2622<references title="Normative References">
2624<reference anchor="Part1">
2625  <front>
2626    <title abbrev="HTTP/1.1">HTTP/1.1, part 1: URIs, Connections, and Message Parsing</title>
2627    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2628      <organization abbrev="Day Software">Day Software</organization>
2629      <address><email></email></address>
2630    </author>
2631    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2632      <organization>One Laptop per Child</organization>
2633      <address><email></email></address>
2634    </author>
2635    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2636      <organization abbrev="HP">Hewlett-Packard Company</organization>
2637      <address><email></email></address>
2638    </author>
2639    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2640      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2641      <address><email></email></address>
2642    </author>
2643    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2644      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2645      <address><email></email></address>
2646    </author>
2647    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2648      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2649      <address><email></email></address>
2650    </author>
2651    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2652      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2653      <address><email></email></address>
2654    </author>
2655    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2656      <organization abbrev="W3C">World Wide Web Consortium</organization>
2657      <address><email></email></address>
2658    </author>
2659    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2660      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2661      <address><email></email></address>
2662    </author>
2663    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2664  </front>
2665  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p1-messaging-&ID-VERSION;"/>
2666  <x:source href="p1-messaging.xml" basename="p1-messaging"/>
2669<reference anchor="Part3">
2670  <front>
2671    <title abbrev="HTTP/1.1">HTTP/1.1, part 3: Message Payload and Content Negotiation</title>
2672    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2673      <organization abbrev="Day Software">Day Software</organization>
2674      <address><email></email></address>
2675    </author>
2676    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2677      <organization>One Laptop per Child</organization>
2678      <address><email></email></address>
2679    </author>
2680    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2681      <organization abbrev="HP">Hewlett-Packard Company</organization>
2682      <address><email></email></address>
2683    </author>
2684    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2685      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2686      <address><email></email></address>
2687    </author>
2688    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2689      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2690      <address><email></email></address>
2691    </author>
2692    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2693      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2694      <address><email></email></address>
2695    </author>
2696    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2697      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2698      <address><email></email></address>
2699    </author>
2700    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2701      <organization abbrev="W3C">World Wide Web Consortium</organization>
2702      <address><email></email></address>
2703    </author>
2704    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2705      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2706      <address><email></email></address>
2707    </author>
2708    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2709  </front>
2710  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p3-payload-&ID-VERSION;"/>
2711  <x:source href="p3-payload.xml" basename="p3-payload"/>
2714<reference anchor="Part4">
2715  <front>
2716    <title abbrev="HTTP/1.1">HTTP/1.1, part 4: Conditional Requests</title>
2717    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2718      <organization abbrev="Day Software">Day Software</organization>
2719      <address><email></email></address>
2720    </author>
2721    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2722      <organization>One Laptop per Child</organization>
2723      <address><email></email></address>
2724    </author>
2725    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2726      <organization abbrev="HP">Hewlett-Packard Company</organization>
2727      <address><email></email></address>
2728    </author>
2729    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2730      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2731      <address><email></email></address>
2732    </author>
2733    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2734      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2735      <address><email></email></address>
2736    </author>
2737    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2738      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2739      <address><email></email></address>
2740    </author>
2741    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2742      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2743      <address><email></email></address>
2744    </author>
2745    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2746      <organization abbrev="W3C">World Wide Web Consortium</organization>
2747      <address><email></email></address>
2748    </author>
2749    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2750      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2751      <address><email></email></address>
2752    </author>
2753    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2754  </front>
2755  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p4-conditional-&ID-VERSION;"/>
2756  <x:source href="p4-conditional.xml" basename="p4-conditional"/>
2759<reference anchor="Part5">
2760  <front>
2761    <title abbrev="HTTP/1.1">HTTP/1.1, part 5: Range Requests and Partial Responses</title>
2762    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2763      <organization abbrev="Day Software">Day Software</organization>
2764      <address><email></email></address>
2765    </author>
2766    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2767      <organization>One Laptop per Child</organization>
2768      <address><email></email></address>
2769    </author>
2770    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2771      <organization abbrev="HP">Hewlett-Packard Company</organization>
2772      <address><email></email></address>
2773    </author>
2774    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2775      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2776      <address><email></email></address>
2777    </author>
2778    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2779      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2780      <address><email></email></address>
2781    </author>
2782    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2783      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2784      <address><email></email></address>
2785    </author>
2786    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2787      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2788      <address><email></email></address>
2789    </author>
2790    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2791      <organization abbrev="W3C">World Wide Web Consortium</organization>
2792      <address><email></email></address>
2793    </author>
2794    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2795      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2796      <address><email></email></address>
2797    </author>
2798    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2799  </front>
2800  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p5-range-&ID-VERSION;"/>
2801  <x:source href="p5-range.xml" basename="p5-range"/>
2804<reference anchor="Part6">
2805  <front>
2806    <title abbrev="HTTP/1.1">HTTP/1.1, part 6: Caching</title>
2807    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2808      <organization abbrev="Day Software">Day Software</organization>
2809      <address><email></email></address>
2810    </author>
2811    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2812      <organization>One Laptop per Child</organization>
2813      <address><email></email></address>
2814    </author>
2815    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2816      <organization abbrev="HP">Hewlett-Packard Company</organization>
2817      <address><email></email></address>
2818    </author>
2819    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2820      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2821      <address><email></email></address>
2822    </author>
2823    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2824      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2825      <address><email></email></address>
2826    </author>
2827    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2828      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2829      <address><email></email></address>
2830    </author>
2831    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2832      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2833      <address><email></email></address>
2834    </author>
2835    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2836      <organization abbrev="W3C">World Wide Web Consortium</organization>
2837      <address><email></email></address>
2838    </author>
2839    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2840      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2841      <address><email></email></address>
2842    </author>
2843    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2844  </front>
2845  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p6-cache-&ID-VERSION;"/>
2846  <x:source href="p6-cache.xml" basename="p6-cache"/>
2849<reference anchor="Part7">
2850  <front>
2851    <title abbrev="HTTP/1.1">HTTP/1.1, part 7: Authentication</title>
2852    <author initials="R." surname="Fielding" fullname="Roy T. Fielding" role="editor">
2853      <organization abbrev="Day Software">Day Software</organization>
2854      <address><email></email></address>
2855    </author>
2856    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2857      <organization>One Laptop per Child</organization>
2858      <address><email></email></address>
2859    </author>
2860    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2861      <organization abbrev="HP">Hewlett-Packard Company</organization>
2862      <address><email></email></address>
2863    </author>
2864    <author initials="H." surname="Frystyk" fullname="Henrik Frystyk Nielsen">
2865      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2866      <address><email></email></address>
2867    </author>
2868    <author initials="L." surname="Masinter" fullname="Larry Masinter">
2869      <organization abbrev="Adobe Systems">Adobe Systems, Incorporated</organization>
2870      <address><email></email></address>
2871    </author>
2872    <author initials="P." surname="Leach" fullname="Paul J. Leach">
2873      <organization abbrev="Microsoft">Microsoft Corporation</organization>
2874      <address><email></email></address>
2875    </author>
2876    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2877      <organization abbrev="W3C/MIT">World Wide Web Consortium</organization>
2878      <address><email></email></address>
2879    </author>
2880    <author initials="Y." surname="Lafon" fullname="Yves Lafon" role="editor">
2881      <organization abbrev="W3C">World Wide Web Consortium</organization>
2882      <address><email></email></address>
2883    </author>
2884    <author initials="J. F." surname="Reschke" fullname="Julian F. Reschke" role="editor">
2885      <organization abbrev="greenbytes">greenbytes GmbH</organization>
2886      <address><email></email></address>
2887    </author>
2888    <date month="&ID-MONTH;" year="&ID-YEAR;"/>
2889  </front>
2890  <seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-p7-auth-&ID-VERSION;"/>
2891  <x:source href="p7-auth.xml" basename="p7-auth"/>
2894<reference anchor="RFC2119">
2895  <front>
2896    <title>Key words for use in RFCs to Indicate Requirement Levels</title>
2897    <author initials="S." surname="Bradner" fullname="Scott Bradner">
2898      <organization>Harvard University</organization>
2899      <address><email></email></address>
2900    </author>
2901    <date month="March" year="1997"/>
2902  </front>
2903  <seriesInfo name="BCP" value="14"/>
2904  <seriesInfo name="RFC" value="2119"/>
2909<references title="Informative References">
2911<reference anchor="RFC1945">
2912  <front>
2913    <title abbrev="HTTP/1.0">Hypertext Transfer Protocol -- HTTP/1.0</title>
2914    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2915      <organization>MIT, Laboratory for Computer Science</organization>
2916      <address><email></email></address>
2917    </author>
2918    <author initials="R.T." surname="Fielding" fullname="Roy T. Fielding">
2919      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2920      <address><email></email></address>
2921    </author>
2922    <author initials="H.F." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2923      <organization>W3 Consortium, MIT Laboratory for Computer Science</organization>
2924      <address><email></email></address>
2925    </author>
2926    <date month="May" year="1996"/>
2927  </front>
2928  <seriesInfo name="RFC" value="1945"/>
2931<reference anchor="RFC2068">
2932  <front>
2933    <title abbrev="HTTP/1.1">Hypertext Transfer Protocol -- HTTP/1.1</title>
2934    <author initials="R." surname="Fielding" fullname="Roy T. Fielding">
2935      <organization>University of California, Irvine, Department of Information and Computer Science</organization>
2936      <address><email></email></address>
2937    </author>
2938    <author initials="J." surname="Gettys" fullname="Jim Gettys">
2939      <organization>MIT Laboratory for Computer Science</organization>
2940      <address><email></email></address>
2941    </author>
2942    <author initials="J." surname="Mogul" fullname="Jeffrey C. Mogul">
2943      <organization>Digital Equipment Corporation, Western Research Laboratory</organization>
2944      <address><email></email></address>
2945    </author>
2946    <author initials="H." surname="Nielsen" fullname="Henrik Frystyk Nielsen">
2947      <organization>MIT Laboratory for Computer Science</organization>
2948      <address><email></email></address>
2949    </author>
2950    <author initials="T." surname="Berners-Lee" fullname="Tim Berners-Lee">
2951      <organization>MIT Laboratory for Computer Science</organization>
2952      <address><email></email></address>
2953    </author>
2954    <date month="January" year="1997"/>
2955  </front>
2956  <seriesInfo name="RFC" value="2068"/>
2959<reference anchor="RFC2616">
2960  <front>
2961    <title>Hypertext Transfer Protocol -- HTTP/1.1</title>
2962    <author initials="R." surname="Fielding" fullname="R. Fielding">
2963      <organization>University of California, Irvine</organization>
2964      <address><email></email></address>
2965    </author>
2966    <author initials="J." surname="Gettys" fullname="J. Gettys">
2967      <organization>W3C</organization>
2968      <address><email></email></address>
2969    </author>
2970    <author initials="J." surname="Mogul" fullname="J. Mogul">
2971      <organization>Compaq Computer Corporation</organization>
2972      <address><email></email></address>
2973    </author>
2974    <author initials="H." surname="Frystyk" fullname="H. Frystyk">
2975      <organization>MIT Laboratory for Computer Science</organization>
2976      <address><email></email></address>
2977    </author>
2978    <author initials="L." surname="Masinter" fullname="L. Masinter">
2979      <organization>Xerox Corporation</organization>
2980      <address><email></email></address>
2981    </author>
2982    <author initials="P." surname="Leach" fullname="P. Leach">
2983      <organization>Microsoft Corporation</organization>
2984      <address><email></email></address>
2985    </author>
2986    <author initials="T." surname="Berners-Lee" fullname="T. Berners-Lee">
2987      <organization>W3C</organization>
2988      <address><email></email></address>
2989    </author>
2990    <date month="June" year="1999"/>
2991  </front>
2992  <seriesInfo name="RFC" value="2616"/>
2995<reference anchor='RFC2817'>
2996  <front>
2997    <title>Upgrading to TLS Within HTTP/1.1</title>
2998    <author initials='R.' surname='Khare' fullname='R. Khare'>
2999      <organization>4K Associates / UC Irvine</organization>
3000      <address><email></email></address>
3001    </author>
3002    <author initials='S.' surname='Lawrence' fullname='S. Lawrence'>
3003      <organization>Agranat Systems, Inc.</organization>
3004      <address><email></email></address>
3005    </author>
3006    <date year='2000' month='May' />
3007  </front>
3008  <seriesInfo name='RFC' value='2817' />
3011<reference anchor='RFC3864'>
3012  <front>
3013    <title>Registration Procedures for Message Header Fields</title>
3014    <author initials='G.' surname='Klyne' fullname='G. Klyne'>
3015      <organization>Nine by Nine</organization>
3016      <address><email></email></address>
3017    </author>
3018    <author initials='M.' surname='Nottingham' fullname='M. Nottingham'>
3019      <organization>BEA Systems</organization>
3020      <address><email></email></address>
3021    </author>
3022    <author initials='J.' surname='Mogul' fullname='J. Mogul'>
3023      <organization>HP Labs</organization>
3024      <address><email></email></address>
3025    </author>
3026    <date year='2004' month='September' />
3027  </front>
3028  <seriesInfo name='BCP' value='90' />
3029  <seriesInfo name='RFC' value='3864' />
3032<reference anchor='RFC5226'>
3033  <front>
3034    <title>Guidelines for Writing an IANA Considerations Section in RFCs</title>
3035    <author initials='T.' surname='Narten' fullname='T. Narten'>
3036      <organization>IBM</organization>
3037      <address><email></email></address>
3038    </author>
3039    <author initials='H.' surname='Alvestrand' fullname='H. Alvestrand'>
3040      <organization>Google</organization>
3041      <address><email></email></address>
3042    </author>
3043    <date year='2008' month='May' />
3044  </front>
3045  <seriesInfo name='BCP' value='26' />
3046  <seriesInfo name='RFC' value='5226' />
3049<reference anchor="RFC5322">
3050  <front>
3051    <title>Internet Message Format</title>
3052    <author initials="P." surname="Resnick" fullname="P. Resnick">
3053      <organization>Qualcomm Incorporated</organization>
3054    </author>
3055    <date year="2008" month="October"/>
3056  </front>
3057  <seriesInfo name="RFC" value="5322"/>
3062<section title="Compatibility with Previous Versions" anchor="compatibility">
3063<section title="Changes from RFC 2068" anchor="changes.from.rfc.2068">
3065   Clarified which error code should be used for inbound server failures
3066   (e.g. DNS failures). (<xref target="status.504"/>).
3069   201 (Created) had a race that required an Etag be sent when a resource is
3070   first created. (<xref target="status.201"/>).
3073   Rewrite of message transmission requirements to make it much harder
3074   for implementors to get it wrong, as the consequences of errors here
3075   can have significant impact on the Internet, and to deal with the
3076   following problems:
3077  <list style="numbers">
3078      <t>Changing "HTTP/1.1 or later" to "HTTP/1.1", in contexts where
3079         this was incorrectly placing a requirement on the behavior of
3080         an implementation of a future version of HTTP/1.x</t>
3082      <t>Made it clear that user-agents should retry requests, not
3083         "clients" in general.</t>
3085      <t>Converted requirements for clients to ignore unexpected 100
3086         (Continue) responses, and for proxies to forward 100 responses,
3087         into a general requirement for 1xx responses.</t>
3089      <t>Modified some TCP-specific language, to make it clearer that
3090         non-TCP transports are possible for HTTP.</t>
3092      <t>Require that the origin server &MUST-NOT; wait for the request
3093         body before it sends a required 100 (Continue) response.</t>
3095      <t>Allow, rather than require, a server to omit 100 (Continue) if
3096         it has already seen some of the request body.</t>
3098      <t>Allow servers to defend against denial-of-service attacks and
3099         broken clients.</t>
3100  </list>
3103   This change adds the Expect header and 417 status code.
3106   Clean up confusion between 403 and 404 responses. (Section <xref target="status.403" format="counter"/>,
3107   <xref target="status.404" format="counter"/>, and <xref target="status.410" format="counter"/>)
3110   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
3111   implemented in previous versions of this specification. See <xref target="RFC2068" x:fmt="of" x:sec="19.6.1"/>.
3115<section title="Changes from RFC 2616" anchor="changes.from.rfc.2616">
3117  This document takes over the Status Code Registry, previously defined
3118  in <xref target="RFC2817" x:fmt="of" x:sec="7.1"/>.
3119  (<xref target="status.code.registry"/>)
3122  Clarify definition of POST.
3123  (<xref target="POST"/>)
3126  Failed to consider that there are
3127  many other request methods that are safe to automatically redirect,
3128  and further that the user agent is able to make that determination
3129  based on the request method semantics.
3130  (Sections <xref format="counter" target="status.301"/>,
3131  <xref format="counter" target="status.302"/> and
3132  <xref format="counter" target="status.307"/>)
3135  Deprecate 305 Use Proxy status code, because user agents did not implement it.
3136  It used to indicate that the requested resource must be accessed through the
3137  proxy given by the Location field. The Location field gave the URI of the
3138  proxy. The recipient was expected to repeat this single request via the proxy.
3139  (<xref target="status.305"/>)
3142  Reclassify Allow header as response header, removing the option to
3143  specify it in a PUT request.
3144  Relax the server requirement on the contents of the Allow header and
3145  remove requirement on clients to always trust the header value.
3146  (<xref target="header.allow"/>)
3149  Correct syntax of Location header to allow fragment,
3150  as referred symbol wasn't what was expected, and add some
3151  clarifications as to when it would not be appropriate.
3152  (<xref target="header.location"/>)
3155  In the description of the Server header, the Via field
3156  was described as a SHOULD. The requirement was and is stated
3157  correctly in the description of the Via header in &header-via;.
3158  (<xref target="header.server"/>)
3164<section title="Collected ABNF" anchor="collected.abnf">
3165   <figure>
3166      <artwork type="abnf" name="p2-semantics.parsed-abnf">Accept = &lt;Accept, defined in [Part3], Section 6.1&gt;&#xD;
3167Accept-Charset = &lt;Accept-Charset, defined in [Part3], Section 6.2&gt;&#xD;
3168Accept-Encoding = &lt;Accept-Encoding, defined in [Part3], Section 6.3&gt;&#xD;
3169Accept-Language = &lt;Accept-Language, defined in [Part3], Section 6.4&gt;&#xD;
3170Accept-Ranges = &lt;Accept-Ranges, defined in [Part5], Section 6.1&gt;&#xD;
3171Age = &lt;Age, defined in [Part6], Section 16.1&gt;&#xD;
3172Allow = "Allow:" OWS Allow-v&#xD;
3173Allow-v = [ ( "," / Method ) *( OWS "," [ OWS Method ] ) ]&#xD;
3174Authorization = &lt;Authorization, defined in [Part7], Section 4.1&gt;&#xD;
3175CR = &lt;CR, defined in [Part1], Section 1.2.2&gt;&#xD;
3176DIGIT = &lt;DIGIT, defined in [Part1], Section 1.2.2&gt;&#xD;
3177ETag = &lt;ETag, defined in [Part4], Section 7.1&gt;&#xD;
3178Expect = "Expect:" OWS Expect-v&#xD;
3179Expect-v = *( "," OWS ) expectation *( OWS "," [ OWS expectation ] )&#xD;
3180From = "From:" OWS From-v&#xD;
3181From-v = mailbox&#xD;
3182HTTP-date = &lt;HTTP-date, defined in [Part1], Section 3.2.1&gt;&#xD;
3183Host = &lt;Host, defined in [Part1], Section 2.1&gt;&#xD;
3184If-Match = &lt;If-Match, defined in [Part4], Section 7.2&gt;&#xD;
3185If-Modified-Since = &lt;If-Modified-Since, defined in [Part4], Section&#xD;
3186 7.3&gt;&#xD;
3187If-None-Match = &lt;If-None-Match, defined in [Part4], Section 7.4&gt;&#xD;
3188If-Range = &lt;If-Range, defined in [Part5], Section 6.3&gt;&#xD;
3189If-Unmodified-Since = &lt;If-Unmodified-Since, defined in [Part4],&#xD;
3190 Section 7.5&gt;&#xD;
3191LF = &lt;LF, defined in [Part1], Section 1.2.2&gt;&#xD;
3192Location = "Location:" OWS Location-v&#xD;
3193Location-v = absolute-URI [ "#" fragment ]&#xD;
3194Max-Forwards = "Max-Forwards:" OWS Max-Forwards-v&#xD;
3195Max-Forwards-v = 1*DIGIT&#xD;
3196Method = %x4F. / %x47.45.54 / %x48.45.41.44 /&#xD;
3197 %x50.4F.53.54 / %x50.55.54 / %x44.45.4C.45.54.45 / %x54.;
3198 / %x43.4F.4E.4E.45.43.54 / extension-method&#xD;
3199OWS = &lt;OWS, defined in [Part1], Section 1.2.2&gt;&#xD;
3200Proxy-Authenticate = &lt;Proxy-Authenticate, defined in [Part7], Section&#xD;
3201 4.2&gt;&#xD;
3202Proxy-Authorization = &lt;Proxy-Authorization, defined in [Part7],&#xD;
3203 Section 4.3&gt;&#xD;
3204RWS = &lt;RWS, defined in [Part1], Section 1.2.2&gt;&#xD;
3205Range = &lt;Range, defined in [Part5], Section 6.4&gt;&#xD;
3206Reason-Phrase = *( WSP / VCHAR / obs-text )&#xD;
3207Referer = "Referer:" OWS Referer-v&#xD;
3208Referer-v = absolute-URI / partial-URI&#xD;
3209Retry-After = "Retry-After:" OWS Retry-After-v&#xD;
3210Retry-After-v = HTTP-date / delta-seconds&#xD;
3211Server = "Server:" OWS Server-v&#xD;
3212Server-v = product *( RWS ( product / comment ) )&#xD;
3213Status-Code = "100" / "101" / "200" / "201" / "202" / "203" / "204" /&#xD;
3214 "205" / "206" / "300" / "301" / "302" / "303" / "304" / "305" /&#xD;
3215 "307" / "400" / "401" / "402" / "403" / "404" / "405" / "406" /&#xD;
3216 "407" / "408" / "409" / "410" / "411" / "412" / "413" / "414" /&#xD;
3217 "415" / "416" / "417" / "500" / "501" / "502" / "503" / "504" /&#xD;
3218 "505" / extension-code&#xD;
3219TE = &lt;TE, defined in [Part1], Section 8.8&gt;&#xD;
3220User-Agent = "User-Agent:" OWS User-Agent-v&#xD;
3221User-Agent-v = product *( RWS ( product / comment ) )&#xD;
3222VCHAR = &lt;VCHAR, defined in [Part1], Section 1.2.2&gt;&#xD;
3223Vary = &lt;Vary, defined in [Part6], Section 16.5&gt;&#xD;
3224WSP = &lt;WSP, defined in [Part1], Section 1.2.2&gt;&#xD;
3225WWW-Authenticate = &lt;WWW-Authenticate, defined in [Part7], Section&#xD;
3226 4.4&gt;&#xD;
3227absolute-URI = &lt;absolute-URI, defined in [Part1], Section 2.1&gt;&#xD;
3228comment = &lt;comment, defined in [Part1], Section 1.2.2&gt;&#xD;
3229delta-seconds = 1*DIGIT&#xD;
3230expect-params = ";" token [ "=" ( token / quoted-string ) ]&#xD;
3231expectation = "100-continue" / expectation-extension&#xD;
3232expectation-extension = token [ "=" ( token / quoted-string )&#xD;
3233 *expect-params ]&#xD;
3234extension-code = 3DIGIT&#xD;
3235extension-method = token&#xD;
3236fragment = &lt;fragment, defined in [Part1], Section 2.1&gt;&#xD;
3237mailbox = &lt;mailbox, defined in [RFC5322], Section 3.4&gt;&#xD;
3238obs-text = &lt;obs-text, defined in [Part1], Section 1.2.2&gt;&#xD;
3239partial-URI = &lt;partial-URI, defined in [Part1], Section 2.1&gt;&#xD;
3240product = &lt;product, defined in [Part1], Section 3.4&gt;&#xD;
3241quoted-string = &lt;quoted-string, defined in [Part1], Section 1.2.2&gt;&#xD;
3242request-header = Accept / Accept-Charset / Accept-Encoding /&#xD;
3243 Accept-Language / Authorization / Expect / From / Host / If-Match /&#xD;
3244 If-Modified-Since / If-None-Match / If-Range / If-Unmodified-Since /&#xD;
3245 Max-Forwards / Proxy-Authorization / Range / Referer / TE /&#xD;
3246 User-Agent&#xD;
3247response-header = Accept-Ranges / Age / Allow / ETag / Location /&#xD;
3248 Proxy-Authenticate / Retry-After / Server / Vary / WWW-Authenticate&#xD;
3249token = &lt;token, defined in [Part1], Section 1.2.2&gt;&#xD;
3250; CR defined but not used&#xD;
3251; LF defined but not used&#xD;
3252; Reason-Phrase defined but not used&#xD;
3253; Status-Code defined but not used&#xD;
3254; request-header defined but not used&#xD;
3255; response-header defined but not used&#xD;
3257   </figure>
3260<section title="Change Log (to be removed by RFC Editor before publication)" anchor="change.log">
3262<section title="Since RFC2616">
3264  Extracted relevant partitions from <xref target="RFC2616"/>.
3268<section title="Since draft-ietf-httpbis-p2-semantics-00">
3270  Closed issues:
3271  <list style="symbols">
3272    <t>
3273      <eref target=""/>:
3274      "Via is a MUST"
3275      (<eref target=""/>)
3276    </t>
3277    <t>
3278      <eref target=""/>:
3279      "Fragments allowed in Location"
3280      (<eref target=""/>)
3281    </t>
3282    <t>
3283      <eref target=""/>:
3284      "Safe Methods vs Redirection"
3285      (<eref target=""/>)
3286    </t>
3287    <t>
3288      <eref target=""/>:
3289      "Revise description of the POST method"
3290      (<eref target=""/>)
3291    </t>
3292    <t>
3293      <eref target=""/>:
3294      "Normative and Informative references"
3295    </t>
3296    <t>
3297      <eref target=""/>:
3298      "RFC2606 Compliance"
3299    </t>
3300    <t>
3301      <eref target=""/>:
3302      "Informative references"
3303    </t>
3304    <t>
3305      <eref target=""/>:
3306      "Redundant cross-references"
3307    </t>
3308  </list>
3311  Other changes:
3312  <list style="symbols">
3313    <t>
3314      Move definitions of 304 and 412 condition codes to <xref target="Part4"/>
3315    </t>
3316  </list>
3320<section title="Since draft-ietf-httpbis-p2-semantics-01">
3322  Closed issues:
3323  <list style="symbols">
3324    <t>
3325      <eref target=""/>:
3326      "PUT side effects"
3327    </t>
3328    <t>
3329      <eref target=""/>:
3330      "Duplicate Host header requirements"
3331    </t>
3332  </list>
3335  Ongoing work on ABNF conversion (<eref target=""/>):
3336  <list style="symbols">
3337    <t>
3338      Move "Product Tokens" section (back) into Part 1, as "token" is used
3339      in the definition of the Upgrade header.
3340    </t>
3341    <t>
3342      Add explicit references to BNF syntax and rules imported from other parts of the specification.
3343    </t>
3344    <t>
3345      Copy definition of delta-seconds from Part6 instead of referencing it.
3346    </t>
3347  </list>
3351<section title="Since draft-ietf-httpbis-p2-semantics-02" anchor="changes.since.02">
3353  Closed issues:
3354  <list style="symbols">
3355    <t>
3356      <eref target=""/>:
3357      "Requiring Allow in 405 responses"
3358    </t>
3359    <t>
3360      <eref target=""/>:
3361      "Status Code Registry"
3362    </t>
3363    <t>
3364      <eref target=""/>:
3365      "Redirection vs. Location"
3366    </t>
3367    <t>
3368      <eref target=""/>:
3369      "Cacheability of 303 response"
3370    </t>
3371    <t>
3372      <eref target=""/>:
3373      "305 Use Proxy"
3374    </t>
3375    <t>
3376      <eref target=""/>:
3377      "Classification for Allow header"
3378    </t>
3379    <t>
3380      <eref target=""/>:
3381      "PUT - 'store under' vs 'store at'"
3382    </t>
3383  </list>
3386  Ongoing work on IANA Message Header Registration (<eref target=""/>):
3387  <list style="symbols">
3388    <t>
3389      Reference RFC 3984, and update header registrations for headers defined
3390      in this document.
3391    </t>
3392  </list>
3395  Ongoing work on ABNF conversion (<eref target=""/>):
3396  <list style="symbols">
3397    <t>
3398      Replace string literals when the string really is case-sensitive (method).
3399    </t>
3400  </list>
3404<section title="Since draft-ietf-httpbis-p2-semantics-03" anchor="changes.since.03">
3406  Closed issues:
3407  <list style="symbols">
3408    <t>
3409      <eref target=""/>:
3410      "OPTIONS request bodies"
3411    </t>
3412    <t>
3413      <eref target=""/>:
3414      "Description of CONNECT should refer to RFC2817"
3415    </t>
3416    <t>
3417      <eref target=""/>:
3418      "Location Content-Location reference request/response mixup"
3419    </t>
3420  </list>
3423  Ongoing work on Method Registry (<eref target=""/>):
3424  <list style="symbols">
3425    <t>
3426      Added initial proposal for registration process, plus initial
3427      content (non-HTTP/1.1 methods to be added by a separate specification).
3428    </t>
3429  </list>
3433<section title="Since draft-ietf-httpbis-p2-semantics-04" anchor="changes.since.04">
3435  Closed issues:
3436  <list style="symbols">
3437    <t>
3438      <eref target=""/>:
3439      "Content-*"
3440    </t>
3441    <t>
3442      <eref target=""/>:
3443      "RFC 2822 is updated by RFC 5322"
3444    </t>
3445  </list>
3448  Ongoing work on ABNF conversion (<eref target=""/>):
3449  <list style="symbols">
3450    <t>
3451      Use "/" instead of "|" for alternatives.
3452    </t>
3453    <t>
3454      Introduce new ABNF rules for "bad" whitespace ("BWS"), optional
3455      whitespace ("OWS") and required whitespace ("RWS").
3456    </t>
3457    <t>
3458      Rewrite ABNFs to spell out whitespace rules, factor out
3459      header value format definitions.
3460    </t>
3461  </list>
3465<section title="Since draft-ietf-httpbis-p2-semantics-05" anchor="changes.since.05">
3467  Closed issues:
3468  <list style="symbols">
3469    <t>
3470      <eref target=""/>:
3471      "Reason-Phrase BNF"
3472    </t>
3473  </list>
3476  Ongoing work on ABNF conversion (<eref target=""/>):
3477  <list style="symbols">
3478    <t>
3479      Add appendix containing collected and expanded ABNF.
3480    </t>
3481  </list>
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