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Content-Encoding

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Revision 936807:

Revision 936807 by teoli on

Revision 1088717:

Revision 1088717 by fscholz on

Title:
Content-Encoding
Content-Encoding
Slug:
Web/HTTP/Headers/Content-Encoding
Web/HTTP/Headers/Content-Encoding
Tags:
HTTP Headers Reference
"HTTP" "Headers" "Reference"
Comment:
update
Content:

Revision 936807
Revision 1088717
nn7    <div>
8      {{HTTPSidebar}}
9    </div>
n8      The <strong><code>Content-Encoding</code></strong> header in11      The <strong><code>Content-Encoding</code></strong> header i
>ndicates which algorithm is been used for this message.>ndicates which algorithm is used for the message.
n10    <p>n13    <table class="properties">
11      Valid values for the <code>Content-Encoding</code> header i
>nclude: 
12    </p>
13    <table align="left" class="standard-table">
n16          <th>n16          <th scope="row">
17            Value17            Header type
n19          <th>n19          <td>
20            Meaning20            {{Glossary("Response header")}}
21          </td>
22        </tr>
23        <tr>
24          <th scope="row">
25            {{Glossary("Forbidden header name")}}
nn27          <td>
28            no
29          </td>
30        </tr>
31      </tbody>
32    </table>
33    <h2 id="Syntax">
34      Syntax
35    </h2>
36    <pre class="syntaxbox">
37Content-Encoding: gzip
38Content-Encoding: compress
39Content-Encoding: deflate
40Content-Encoding: identity
41Content-Encoding: br
42</pre>
43    <h2 id="Directives">
44      Directives
45    </h2>
46    <dl>
47      <dt>
48        <code>gzip</code>
49      </dt>
50      <dd>
51        A format using the <a class="external" href="http://en.wi
 >kipedia.org/wiki/LZ77_and_LZ78#LZ77">Lempel-Ziv coding</a> (LZ77)
 >, with a 32-bit CRC. This is originally the format of the UNIX <e
 >m>gzip</em> program. The HTTP/1.1 standard also recommends that t
 >he servers supporting this content-encoding should recognize <cod
 >e>x-gzip</code> as an alias, for compatibility purposes.
52      </dd>
53      <dt>
54        <code>compress</code>
55      </dt>
56      <dd>
57        A format using the <a class="external" href="http://en.wi
 >kipedia.org/wiki/LZW">Lempel-Ziv-Welch</a> (LZW) algorithm. The v
 >alue name was taken from the UNIX <em>compress</em> program, whic
 >h implemented this algorithm.<br>
58        Like the compress program, which has disappeared from mos
 >t UNIX distributions, this content-encoding is used by almost no 
 >browsers today, partly because of a patent issue (which expired i
 >n 2003).
59      </dd>
60      <dt>
61        <code>deflate</code>
62      </dt>
63      <dd>
64        Using the <a class="external" href="http://en.wikipedia.o
 >rg/wiki/Zlib">zlib</a> structure (defined in <a class="external" 
 >href="http://tools.ietf.org/html/rfc1950">RFC 1950</a>), with the
 > <a class="external" href="http://en.wikipedia.org/wiki/DEFLATE">
 ><em>deflate</em></a> compression algorithm (defined in <a class="
 >external" href="http://tools.ietf.org/html/rfc1952">RFC 1951</a>)
 >.
65      </dd>
66      <dt>
67        <code>identity</code>
68      </dt>
69      <dd>
70        Indicates the identity function (i.e. no compression, nor
 > modification). This token, except if explicitly specified, is al
 >ways deemed acceptable.
71      </dd>
72      <dt>
73        br
74      </dt>
75      <dd>
76        A format using the <a href="https://en.wikipedia.org/wiki
 >/Brotli">Brotli</a> algorithm
77      </dd>
78    </dl>
79    <h2 id="Examples">
80      Examples
81    </h2>
82    <h3 id="Preventing_caching">
83      Compressing with gzip
84    </h3>
85    <pre>
86Content-Encoding: gzip
87</pre>
88    <h2 id="Specifications">
89      Specifications
90    </h2>
91    <table class="standard-table">
92      <tbody>
93        <tr>
94          <th scope="col">
95            Specification
22          <th>96          </th>
23            Standard97          <th scope="col">
98            Title
n28            <code>gzip</code>n103            {{RFC("7231", "Content-Encoding", "3.1.2.2")}}
n31            <p>n106            Hypertext Transfer Protocol (HTTP/1.1): Semantics and
 > Content
32              A format using the <a class="external" href="http:/
>/en.wikipedia.org/wiki/LZ77_and_LZ78#LZ77" title="http://en.wikip 
>edia.org/wiki/LZ77_and_LZ78#LZ77">Lempel-Ziv coding</a> (LZ77), w 
>ith a 32-bit CRC. This is originally the format of the UNIX <em>g 
>zip</em> program. The HTTP/1.1 standard also recommends that the  
>servers supporting this content-encoding should recognize <code>x 
>-gzip</code> as an alias, for compatibility purposes. 
33            </p>
34          </td>
35          <td>
36            <a class="external" href="http://tools.ietf.org/html/
>rfc1952" title="http://tools.ietf.org/html/rfc1952">RFC 1952</a> 
37          </td>
38        </tr>
39        <tr>
40          <td>
41            <code>compress</code>
42          </td>
43          <td>
44            A format using the <a class="external" href="http://e
>n.wikipedia.org/wiki/LZW" title="http://en.wikipedia.org/wiki/LZW 
>">Lempel-Ziv-Welch</a> (LZW) algorithm. The value name was taken  
>from the UNIX <em>compress</em> program, which implemented this a 
>lgorithm.<br> 
45            Like the compress program, which has disappeared from
> most UNIX distributions, this content-encoding is used by almost 
> no browsers today, partly because of a patent issue (which expir 
>ed in 2003). 
46          </td>
47          <td>
48            HTTP/1.1
49          </td>
50        </tr>
51        <tr>
52          <td>
53            <code>deflate</code>
54          </td>
55          <td>
56            Using the <a class="external" href="http://en.wikiped
>ia.org/wiki/Zlib" title="http://en.wikipedia.org/wiki/Zlib">zlib< 
>/a> structure (defined in <a class="external" href="http://tools. 
>ietf.org/html/rfc1950" title="http://tools.ietf.org/html/rfc1950" 
>>RFC 1950</a>), with the <a class="external" href="http://en.wiki 
>pedia.org/wiki/DEFLATE" title="http://en.wikipedia.org/wiki/DEFLA 
>TE"><em>deflate</em></a> compression algorithm (defined in <a cla 
>ss="external" href="http://tools.ietf.org/html/rfc1952" title="ht 
>tp://tools.ietf.org/html/rfc1952">RFC 1951</a>). 
57          </td>
58          <td>
59            <a class="external" href="http://tools.ietf.org/html/
>rfc1950" title="http://tools.ietf.org/html/rfc1950">RFC 1950</a>  
>and <a class="external" href="http://tools.ietf.org/html/rfc1951" 
> title="http://tools.ietf.org/html/rfc1951">RFC 1951</a> 
60          </td>
61        </tr>
62        <tr>
63          <td>
64            <code>identity</code>
65          </td>
66          <td>
67            Indicates the identity function (i.e. no compression,
> nor modification). This token, except if explicitly specified, i 
>s always deemed acceptable. 
68          </td>
69          <td>
70            HTTP/1.1
71          </td>
72        </tr>
73        <tr>
74          <td>
75            <code>br</code>
76          </td>
77          <td>
78            A format using the <a href="https://en.wikipedia.org/
>wiki/Brotli">Brotli</a> algorithm 
79          </td>
80          <td>
81            <em>Experimental</em>
nn111    <h2 id="Browser_compatibility">
112      Browser compatibility
113    </h2>
114    <p class="hidden">
115      To contribute to this compatibility data, please write a pu
 >ll request against this file: <a href="https://github.com/mdn/bro
 >wser-compat-data/blob/master/http/headers.json">https://github.co
 >m/mdn/browser-compat-data/blob/master/http/headers.json</a>.
116    </p>
n87      &nbsp;n118      {{Compat}}
tt120    <h2 id="See_also">
121      See also
122    </h2>
123    <ul>
124      <li>{{HTTPHeader("Accept-Encoding")}}
125      </li>
126      <li>{{HTTPHeader("Transfer-Encoding")}}
127      </li>
128    </ul>

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