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<div id="preamble"><h1>Apache Module mod_brotli</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="../en/mod/mod_brotli.html" title="English">&nbsp;en&nbsp;</a> |
<a href="../fr/mod/mod_brotli.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a></p>
</div>
<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Compress content via Brotli 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>brotli_module</td></tr>
<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_brotli.c</td></tr>
<tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Available in version 2.4.26 and later.</td></tr></table>
<h3>Summary</h3>
<p>The <code class="module"><a href="../mod/mod_brotli.html">mod_brotli</a></code> module provides
the <code>BROTLI_COMPRESS</code> output filter that allows output from
your server to be compressed using the brotli compression format before being sent to the client over
the network. This module uses the Brotli library found at
<a href="https://github.com/google/brotli">https://github.com/google/brotli</a>.</p>
</div>
<div id="quickview"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><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>
<li><img alt="" src="../images/down.gif" /> <a href="#precompressed">Serving pre-compressed
content</a></li>
</ul><h3 class="directives">Directives</h3>
<ul id="toc">
<li><img alt="" src="../images/down.gif" /> <a href="#brotlialteretag">BrotliAlterETag</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#brotlicompressionmaxinputblock">BrotliCompressionMaxInputBlock</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#brotlicompressionquality">BrotliCompressionQuality</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#brotlicompressionwindow">BrotliCompressionWindow</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#brotlifilternote">BrotliFilterNote</a></li>
</ul>
<h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&amp;list_id=144532&amp;product=Apache%20httpd-2&amp;query_format=specific&amp;order=changeddate%20DESC%2Cpriority%2Cbug_severity&amp;component=mod_brotli">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&amp;component=mod_brotli">Report a bug</a></li></ul><h3>See also</h3>
<ul class="seealso">
<li><a href="../filter.html">Filters</a></li>
<li><a href="#comments_section">Comments</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>
<div class="warning"><h3>Compression and TLS</h3>
<p>Some web applications are vulnerable to an information disclosure
attack when a TLS connection carries compressed data. For more
information, review the details of the "BREACH" family of attacks.</p>
</div>
<p>This is a simple configuration that compresses common text-based content types.</p>
<div class="example"><h3>Compress only a few types</h3><pre class="prettyprint lang-config">AddOutputFilterByType BROTLI_COMPRESS text/html text/plain text/xml text/css text/javascript application/javascript</pre>
</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>
<div class="warning"><h3>Compression and TLS</h3>
<p>Some web applications are vulnerable to an information disclosure
attack when a TLS connection carries compressed data. For more
information, review the details of the "BREACH" family of attacks.</p>
</div>
<h3><a name="output" id="output">Output Compression</a></h3>
<p>Compression is implemented by the <code>BROTLI_COMPRESS</code>
<a href="../filter.html">filter</a>. The following directive
will enable compression for documents in the container where it
is placed:</p>
<pre class="prettyprint lang-config">SetOutputFilter BROTLI_COMPRESS
SetEnvIfNoCase Request_URI \.(?:gif|jpe?g|png)$ no-brotli</pre>
<p>If you want to restrict the compression to particular MIME types
in general, you may use the <code class="directive"><a href="../mod/mod_filter.html#addoutputfilterbytype">AddOutputFilterByType</a></code> directive. Here is an example of
enabling compression only for the html files of the Apache
documentation:</p>
<pre class="prettyprint lang-config">&lt;Directory "/your-server-root/manual"&gt;
AddOutputFilterByType BROTLI_COMPRESS text/html
&lt;/Directory&gt;</pre>
<div class="note"><h3>Note</h3>
The <code>BROTLI_COMPRESS</code> filter is always inserted after RESOURCE
filters like PHP or SSI. It never touches internal subrequests.
</div>
<div class="note"><h3>Note</h3>
There is an environment variable <code>no-brotli</code>,
set via <code class="directive"><a href="../mod/mod_env.html#setenv">SetEnv</a></code>, which
will disable brotli compression for a particular request, even if
it is supported by the client.
</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_brotli.html">mod_brotli</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>BROTLI_COMPRESS</code>
filter depends on the <code>User-Agent</code>, you should add:</p>
<pre class="prettyprint lang-config">Header append Vary User-Agent</pre>
<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><pre class="prettyprint lang-config">Header set Vary *</pre>
</div>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="precompressed" id="precompressed">Serving pre-compressed
content</a></h2>
<p>Since <code class="module"><a href="../mod/mod_brotli.html">mod_brotli</a></code> re-compresses content each
time a request is made, some performance benefit can be derived by
pre-compressing the content and telling mod_brotli to serve them
without re-compressing them. This may be accomplished using a
configuration like the following:</p>
<pre class="prettyprint lang-config">&lt;IfModule mod_headers.c&gt;
# Serve brotli compressed CSS files if they exist
# and the client accepts brotli.
RewriteCond "%{HTTP:Accept-encoding}" "br"
RewriteCond "%{REQUEST_FILENAME}\.br" "-s"
RewriteRule "^(.*)\.css" "$1\.css\.br" [QSA]
# Serve brotli compressed JS files if they exist
# and the client accepts brotli.
RewriteCond "%{HTTP:Accept-encoding}" "br"
RewriteCond "%{REQUEST_FILENAME}\.br" "-s"
RewriteRule "^(.*)\.js" "$1\.js\.br" [QSA]
# Serve correct content types, and prevent double compression.
RewriteRule "\.css\.br$" "-" [T=text/css,E=no-brotli:1]
RewriteRule "\.js\.br$" "-" [T=text/javascript,E=no-brotli:1]
&lt;FilesMatch "(\.js\.br|\.css\.br)$"&gt;
# Serve correct encoding type.
Header append Content-Encoding br
# Force proxies to cache brotli &amp;
# non-brotli css/js files separately.
Header append Vary Accept-Encoding
&lt;/FilesMatch&gt;
&lt;/IfModule&gt;</pre>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="BrotliAlterETag" id="BrotliAlterETag">BrotliAlterETag</a> <a name="brotlialteretag" id="brotlialteretag">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>How the outgoing ETag header should be modified during compression</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>BrotliAlterETag AddSuffix|NoChange|Remove</code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>BrotliAlterETag AddSuffix</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_brotli</td></tr>
</table>
<p>The <code class="directive">BrotliAlterETag</code> directive specifies
how the ETag hader should be altered when a response is compressed.</p>
<dl>
<dt>AddSuffix</dt>
<dd><p>Append the compression method onto the end of the ETag, causing
compressed and uncompressed representations to have unique ETags.
In another dynamic compression module, mod_deflate, this has been
the default since 2.4.0. This setting prevents serving "HTTP Not
Modified" (304) responses to conditional requests for compressed
content.</p></dd>
<dt>NoChange</dt>
<dd><p>Don't change the ETag on a compressed response. In another dynamic
compression module, mod_deflate, this has been the default prior to
2.4.0. This setting does not satisfy the HTTP/1.1 property that all
representations of the same resource have unique ETags. </p></dd>
<dt>Remove</dt>
<dd><p>Remove the ETag header from compressed responses. This prevents
some conditional requests from being possible, but avoids the
shortcomings of the preceding options. </p></dd>
</dl>
</div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="directive-section"><h2><a name="BrotliCompressionMaxInputBlock" id="BrotliCompressionMaxInputBlock">BrotliCompressionMaxInputBlock</a> <a name="brotlicompressionmaxinputblock" id="brotlicompressionmaxinputblock">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Maximum input block size</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>BrotliCompressionMaxInputBlock <var>value</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>(automatic)</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_brotli</td></tr>
</table>
<p>The <code class="directive">BrotliCompressionMaxInputBlock</code> directive specifies
the maximum input block size between 16 and 24, with the caveat that
larger block sizes require more memory.</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="BrotliCompressionQuality" id="BrotliCompressionQuality">BrotliCompressionQuality</a> <a name="brotlicompressionquality" id="brotlicompressionquality">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Compression quality</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>BrotliCompressionQuality <var>value</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>BrotliCompressionQuality 5</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_brotli</td></tr>
</table>
<p>The <code class="directive">BrotliCompressionQuality</code> directive specifies
the compression quality (a value between 0 and 11). Higher quality values
result in better, but also slower 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="BrotliCompressionWindow" id="BrotliCompressionWindow">BrotliCompressionWindow</a> <a name="brotlicompressionwindow" id="brotlicompressionwindow">Directive</a></h2>
<table class="directive">
<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Brotli sliding compression window size</td></tr>
<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>BrotliCompressionWindow <var>value</var></code></td></tr>
<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>BrotliCompressionWindow 18</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_brotli</td></tr>
</table>
<p>The <code class="directive">BrotliCompressionWindow</code> directive specifies the
brotli sliding compression window size (a value between 10 and 24). Larger
window sizes can improve compression quality, but require more memory.</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="BrotliFilterNote" id="BrotliFilterNote">BrotliFilterNote</a> <a name="brotlifilternote" id="brotlifilternote">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>BrotliFilterNote [<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_brotli</td></tr>
</table>
<p>The <code class="directive">BrotliFilterNote</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><pre class="prettyprint lang-config">BrotliFilterNote ratio
LogFormat '"%r" %b (%{ratio}n) "%{User-agent}i"' brotli
CustomLog "logs/brotli_log" brotli</pre>
</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 a 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><pre class="prettyprint lang-config">BrotliFilterNote Input instream
BrotliFilterNote Output outstream
BrotliFilterNote Ratio ratio
LogFormat '"%r" %{outstream}n/%{instream}n (%{ratio}n%%)' brotli
CustomLog "logs/brotli_log" brotli</pre>
</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>
<div class="bottomlang">
<p><span>Available Languages: </span><a href="../en/mod/mod_brotli.html" title="English">&nbsp;en&nbsp;</a> |
<a href="../fr/mod/mod_brotli.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a></p>
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