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| <title>mod_deflate - Apache HTTP Server</title> |
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| <p class="apache">Apache HTTP Server Version 2.0</p> |
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| <div class="retired"><h4>Please note</h4> |
| <p>This document refers to the <strong>2.0</strong> version of Apache httpd, which <strong>is no longer maintained</strong>. Upgrade, and refer to the current version of httpd instead, documented at:</p> |
| <ul><li><a href="http://httpd.apache.org/docs/current/">Current release version of Apache HTTP Server documentation</a></li></ul><p>You may follow <a href="http://httpd.apache.org/docs/current/mod/mod_deflate.html">this link</a> to go to the current version of this document.</p></div><div id="preamble"><h1>Apache Module mod_deflate</h1> |
| <div class="toplang"> |
| <p><span>Available Languages: </span><a href="../en/mod/mod_deflate.html" title="English"> en </a> | |
| <a href="../ja/mod/mod_deflate.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | |
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| </div> |
| <table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Compress content before it is delivered to the |
| client</td></tr> |
| <tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr> |
| <tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>deflate_module</td></tr> |
| <tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_deflate.c</td></tr></table> |
| <h3>Summary</h3> |
| |
| <p>The <code class="module"><a href="../mod/mod_deflate.html">mod_deflate</a></code> module provides |
| the <code>DEFLATE</code> output filter that allows output from |
| your server to be compressed before being sent to the client over |
| the network.</p> |
| </div> |
| <div id="quickview"><h3 class="directives">Directives</h3> |
| <ul id="toc"> |
| <li><img alt="" src="../images/down.gif" /> <a href="#deflatebuffersize">DeflateBufferSize</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#deflatecompressionlevel">DeflateCompressionLevel</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#deflatefilternote">DeflateFilterNote</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#deflatememlevel">DeflateMemLevel</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#deflatewindowsize">DeflateWindowSize</a></li> |
| </ul> |
| <h3>Topics</h3> |
| <ul id="topics"> |
| <li><img alt="" src="../images/down.gif" /> <a href="#recommended">Sample Configurations</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#enable">Enabling Compression</a></li> |
| <li><img alt="" src="../images/down.gif" /> <a href="#proxies">Dealing with proxy servers</a></li> |
| </ul><h3>See also</h3> |
| <ul class="seealso"> |
| <li><a href="../filter.html">Filters</a></li> |
| </ul></div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="section"> |
| <h2><a name="recommended" id="recommended">Sample Configurations</a></h2> |
| <p>This is a simple sample configuration for the impatient.</p> |
| |
| <div class="example"><h3>Compress only a few types</h3><p><code> |
| AddOutputFilterByType DEFLATE text/html text/plain text/xml |
| </code></p></div> |
| |
| <p>The following configuration, while resulting in more compressed content, |
| is also much more complicated. Do not use this unless you fully understand |
| all the configuration details.</p> |
| |
| <div class="example"><h3>Compress everything except images</h3><p><code> |
| <Location /><br /> |
| <span class="indent"> |
| # Insert filter<br /> |
| SetOutputFilter DEFLATE<br /> |
| <br /> |
| # Netscape 4.x has some problems...<br /> |
| BrowserMatch ^Mozilla/4 gzip-only-text/html<br /> |
| <br /> |
| # Netscape 4.06-4.08 have some more problems<br /> |
| BrowserMatch ^Mozilla/4\.0[678] no-gzip<br /> |
| <br /> |
| # MSIE masquerades as Netscape, but it is fine<br /> |
| # BrowserMatch \bMSIE !no-gzip !gzip-only-text/html<br /> |
| <br /> |
| # NOTE: Due to a bug in mod_setenvif up to Apache 2.0.48<br /> |
| # the above regex won't work. You can use the following<br /> |
| # workaround to get the desired effect:<br /> |
| BrowserMatch \bMSI[E] !no-gzip !gzip-only-text/html<br /> |
| <br /> |
| # Don't compress images<br /> |
| SetEnvIfNoCase Request_URI \<br /> |
| <span class="indent"> |
| \.(?:gif|jpe?g|png)$ no-gzip dont-vary<br /> |
| </span> |
| <br /> |
| # Make sure proxies don't deliver the wrong content<br /> |
| Header append Vary User-Agent env=!dont-vary<br /> |
| </span> |
| </Location> |
| </code></p></div> |
| |
| </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="section"> |
| <h2><a name="enable" id="enable">Enabling Compression</a></h2> |
| |
| <h3><a name="output" id="output">Output Compression</a></h3> |
| <p>Compression is implemented by the <code>DEFLATE</code> |
| <a href="../filter.html">filter</a>. The following directive |
| will enable compression for documents in the container where it |
| is placed:</p> |
| |
| <div class="example"><p><code> |
| SetOutputFilter DEFLATE |
| </code></p></div> |
| |
| <p>Some popular browsers cannot handle compression of all content |
| so you may want to set the <code>gzip-only-text/html</code> note to |
| <code>1</code> to only allow html files to be compressed (see |
| below). If you set this to <em>anything but <code>1</code></em> it |
| will be ignored.</p> |
| |
| <p>If you want to restrict the compression to particular MIME types |
| in general, you may use the <code class="directive"><a href="../mod/core.html#addoutputfilterbytype">AddOutputFilterByType</a></code> directive. Here is an example of |
| enabling compression only for the html files of the Apache |
| documentation:</p> |
| |
| <div class="example"><p><code> |
| <Directory "/your-server-root/manual"><br /> |
| <span class="indent"> |
| AddOutputFilterByType DEFLATE text/html<br /> |
| </span> |
| </Directory> |
| </code></p></div> |
| |
| <p>For browsers that have problems even with compression of all file |
| types, use the <code class="directive"><a href="../mod/mod_setenvif.html#browsermatch">BrowserMatch</a></code> directive to set the <code>no-gzip</code> |
| note for that particular browser so that no compression will be |
| performed. You may combine <code>no-gzip</code> with <code>gzip-only-text/html</code> to get the best results. In that case |
| the former overrides the latter. Take a look at the following |
| excerpt from the <a href="#recommended">configuration example</a> |
| defined in the section above:</p> |
| |
| <div class="example"><p><code> |
| BrowserMatch ^Mozilla/4 gzip-only-text/html<br /> |
| BrowserMatch ^Mozilla/4\.0[678] no-gzip<br /> |
| BrowserMatch \bMSIE !no-gzip !gzip-only-text/html |
| </code></p></div> |
| |
| <p>At first we probe for a <code>User-Agent</code> string that |
| indicates a Netscape Navigator version of 4.x. These versions |
| cannot handle compression of types other than |
| <code>text/html</code>. The versions 4.06, 4.07 and 4.08 also |
| have problems with decompressing html files. Thus, we completely |
| turn off the deflate filter for them.</p> |
| |
| <p>The third <code class="directive"><a href="../mod/mod_setenvif.html#browsermatch">BrowserMatch</a></code> |
| directive fixes the guessed identity of the user agent, because |
| the Microsoft Internet Explorer identifies itself also as "Mozilla/4" |
| but is actually able to handle requested compression. Therefore we |
| match against the additional string "MSIE" (<code>\b</code> means |
| "word boundary") in the <code>User-Agent</code> Header and turn off |
| the restrictions defined before.</p> |
| |
| <div class="note"><h3>Note</h3> |
| The <code>DEFLATE</code> filter is always inserted after RESOURCE |
| filters like PHP or SSI. It never touches internal subrequests. |
| </div> |
| |
| |
| <h3><a name="input" id="input">Input Decompression</a></h3> |
| <p>The <code class="module"><a href="../mod/mod_deflate.html">mod_deflate</a></code> module also provides a filter for |
| decompressing a gzip compressed request body . In order to activate |
| this feature you have to insert the <code>DEFLATE</code> filter into |
| the input filter chain using <code class="directive"><a href="../mod/core.html#setinputfilter">SetInputFilter</a></code> or <code class="directive"><a href="../mod/mod_mime.html#addinputfilter">AddInputFilter</a></code>, for example:</p> |
| |
| <div class="example"><p><code> |
| <Location /dav-area><br /> |
| <span class="indent"> |
| SetInputFilter DEFLATE<br /> |
| </span> |
| </Location> |
| </code></p></div> |
| |
| <p>Now if a request contains a <code>Content-Encoding: |
| gzip</code> header, the body will be automatically decompressed. |
| Few browsers have the ability to gzip request bodies. However, |
| some special applications actually do support request |
| compression, for instance some <a href="http://www.webdav.org">WebDAV</a> clients.</p> |
| |
| <div class="warning"><h3>Note on Content-Length</h3> |
| <p>If you evaluate the request body yourself, <em>don't trust |
| the <code>Content-Length</code> header!</em> |
| The Content-Length header reflects the length of the |
| incoming data from the client and <em>not</em> the byte count of |
| the decompressed data stream.</p> |
| </div> |
| |
| </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="section"> |
| <h2><a name="proxies" id="proxies">Dealing with proxy servers</a></h2> |
| |
| <p>The <code class="module"><a href="../mod/mod_deflate.html">mod_deflate</a></code> module sends a <code>Vary: |
| Accept-Encoding</code> HTTP response header to alert proxies that |
| a cached response should be sent only to clients that send the |
| appropriate <code>Accept-Encoding</code> request header. This |
| prevents compressed content from being sent to a client that will |
| not understand it.</p> |
| |
| <p>If you use some special exclusions dependent |
| on, for example, the <code>User-Agent</code> header, you must |
| manually configure an addition to the <code>Vary</code> header |
| to alert proxies of the additional restrictions. For example, |
| in a typical configuration where the addition of the <code>DEFLATE</code> |
| filter depends on the <code>User-Agent</code>, you should add:</p> |
| |
| <div class="example"><p><code> |
| Header append Vary User-Agent |
| </code></p></div> |
| |
| <p>If your decision about compression depends on other information |
| than request headers (<em>e.g.</em> HTTP version), you have to set the |
| <code>Vary</code> header to the value <code>*</code>. This prevents |
| compliant proxies from caching entirely.</p> |
| |
| <div class="example"><h3>Example</h3><p><code> |
| Header set Vary * |
| </code></p></div> |
| </div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="directive-section"><h2><a name="DeflateBufferSize" id="DeflateBufferSize">DeflateBufferSize</a> <a name="deflatebuffersize" id="deflatebuffersize">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Fragment size to be compressed at one time by zlib</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DeflateBufferSize <var>value</var></code></td></tr> |
| <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>DeflateBufferSize 8096</code></td></tr> |
| <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr> |
| <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> |
| <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_deflate</td></tr> |
| </table> |
| <p>The <code class="directive">DeflateBufferSize</code> directive specifies |
| the size in bytes of the fragments that zlib should compress at one |
| time.</p> |
| |
| </div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="directive-section"><h2><a name="DeflateCompressionLevel" id="DeflateCompressionLevel">DeflateCompressionLevel</a> <a name="deflatecompressionlevel" id="deflatecompressionlevel">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>How much compression do we apply to the output</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DeflateCompressionLevel <var>value</var></code></td></tr> |
| <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>Zlib's default</code></td></tr> |
| <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr> |
| <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> |
| <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_deflate</td></tr> |
| <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td>This directive is available since Apache 2.0.45</td></tr> |
| </table> |
| <p>The <code class="directive">DeflateCompressionLevel</code> directive specifies |
| what level of compression should be used, the higher the value, |
| the better the compression, but the more CPU time is required to |
| achieve this.</p> |
| <p>The value must between 1 (less compression) and 9 (more compression).</p> |
| |
| </div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="directive-section"><h2><a name="DeflateFilterNote" id="DeflateFilterNote">DeflateFilterNote</a> <a name="deflatefilternote" id="deflatefilternote">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Places the compression ratio in a note for logging</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DeflateFilterNote [<var>type</var>] <var>notename</var></code></td></tr> |
| <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr> |
| <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> |
| <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_deflate</td></tr> |
| <tr><th><a href="directive-dict.html#Compatibility">Compatibility:</a></th><td><var>type</var> is available since Apache 2.0.45</td></tr> |
| </table> |
| <p>The <code class="directive">DeflateFilterNote</code> directive |
| specifies that a note about compression ratios should be attached |
| to the request. The name of the note is the value specified for |
| the directive. You can use that note for statistical purposes by |
| adding the value to your <a href="../logs.html#accesslog">access log</a>.</p> |
| |
| <div class="example"><h3>Example</h3><p><code> |
| DeflateFilterNote ratio<br /> |
| <br /> |
| LogFormat '"%r" %b (%{ratio}n) "%{User-agent}i"' deflate<br /> |
| CustomLog logs/deflate_log deflate |
| </code></p></div> |
| |
| <p>If you want to extract more accurate values from your logs, you |
| can use the <var>type</var> argument to specify the type of data |
| left as note for logging. <var>type</var> can be one of:</p> |
| |
| <dl> |
| <dt><code>Input</code></dt> |
| <dd>Store the byte count of the filter's input stream in the note.</dd> |
| |
| <dt><code>Output</code></dt> |
| <dd>Store the byte count of the filter's output stream in the note.</dd> |
| |
| <dt><code>Ratio</code></dt> |
| <dd>Store the compression ratio (<code>output/input * 100</code>) |
| in the note. This is the default, if the <var>type</var> argument |
| is omitted.</dd> |
| </dl> |
| |
| <p>Thus you may log it this way:</p> |
| |
| <div class="example"><h3>Accurate Logging</h3><p><code> |
| DeflateFilterNote Input instream<br /> |
| DeflateFilterNote Output outstream<br /> |
| DeflateFilterNote Ratio ratio<br /> |
| <br /> |
| LogFormat '"%r" %{outstream}n/%{instream}n (%{ratio}n%%)' deflate<br /> |
| CustomLog logs/deflate_log deflate |
| </code></p></div> |
| |
| <h3>See also</h3> |
| <ul> |
| <li><code class="module"><a href="../mod/mod_log_config.html">mod_log_config</a></code></li> |
| </ul> |
| </div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="directive-section"><h2><a name="DeflateMemLevel" id="DeflateMemLevel">DeflateMemLevel</a> <a name="deflatememlevel" id="deflatememlevel">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>How much memory should be used by zlib for compression</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DeflateMemLevel <var>value</var></code></td></tr> |
| <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>DeflateMemLevel 9</code></td></tr> |
| <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr> |
| <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> |
| <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_deflate</td></tr> |
| </table> |
| <p>The <code class="directive">DeflateMemLevel</code> directive specifies |
| how much memory should be used by zlib for compression |
| (a value between 1 and 9).</p> |
| |
| </div> |
| <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> |
| <div class="directive-section"><h2><a name="DeflateWindowSize" id="DeflateWindowSize">DeflateWindowSize</a> <a name="deflatewindowsize" id="deflatewindowsize">Directive</a></h2> |
| <table class="directive"> |
| <tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Zlib compression window size</td></tr> |
| <tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>DeflateWindowSize <var>value</var></code></td></tr> |
| <tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>DeflateWindowSize 15</code></td></tr> |
| <tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr> |
| <tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> |
| <tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_deflate</td></tr> |
| </table> |
| <p>The <code class="directive">DeflateWindowSize</code> directive specifies the |
| zlib compression window size (a value between 1 and 15). Generally, the |
| higher the window size, the higher can the compression ratio be expected.</p> |
| |
| </div> |
| </div> |
| <div class="bottomlang"> |
| <p><span>Available Languages: </span><a href="../en/mod/mod_deflate.html" title="English"> en </a> | |
| <a href="../ja/mod/mod_deflate.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | |
| <a href="../ko/mod/mod_deflate.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p> |
| </div><div id="footer"> |
| <p class="apache">Copyright 2013 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p> |
| <p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div> |
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