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+<div id="page-content">
+<div id="preamble"><h1>Apache Module mod_expires</h1>
+<div class="toplang">
+<p><span>Available Languages: </span><a href="../en/mod/mod_expires.html" title="English">&nbsp;en&nbsp;</a> |
+<a href="../fr/mod/mod_expires.html" hreflang="fr" rel="alternate" title="Français">&nbsp;fr&nbsp;</a> |
+<a href="../ja/mod/mod_expires.html" hreflang="ja" rel="alternate" title="Japanese">&nbsp;ja&nbsp;</a> |
+<a href="../ko/mod/mod_expires.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
+</div>
+<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Generation of <code>Expires</code> and
+<code>Cache-Control</code> HTTP headers according to user-specified
+criteria</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>expires_module</td></tr>
+<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_expires.c</td></tr></table>
+<h3>Summary</h3>
+
+ <p>This module controls the setting of the <code>Expires</code>
+ HTTP header and the <code>max-age</code> directive of the
+ <code>Cache-Control</code> HTTP header in server responses. The
+ expiration date can set to be relative to either the time the
+ source file was last modified, or to the time of the client
+ access.</p>
+
+ <p>These HTTP headers are an instruction to the client about the
+ document's validity and persistence. If cached, the document may
+ be fetched from the cache rather than from the source until this
+ time has passed. After that, the cache copy is considered
+ "expired" and invalid, and a new copy must be obtained from the
+ source.</p>
+
+ <p>To modify <code>Cache-Control</code> directives other than
+ <code>max-age</code> (see <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9">RFC
+ 2616 section 14.9</a>), you can use the <code class="directive"><a href="../mod/mod_headers.html#header">Header</a></code> directive.</p>
+
+ <p> When the <code>Expires</code> header is already part of the response
+ generated by the server, for example when generated by a CGI script or
+ proxied from an origin server, this module does not change or add
+ an <code>Expires</code> or <code>Cache-Control</code> header.</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="#AltSyn">Alternate Interval Syntax</a></li>
+</ul><h3 class="directives">Directives</h3>
+<ul id="toc">
+<li><img alt="" src="../images/down.gif" /> <a href="#expiresactive">ExpiresActive</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#expiresbytype">ExpiresByType</a></li>
+<li><img alt="" src="../images/down.gif" /> <a href="#expiresdefault">ExpiresDefault</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_expires">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&amp;component=mod_expires">Report a bug</a></li></ul><h3>See also</h3>
+<ul class="seealso">
+<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="AltSyn" id="AltSyn">Alternate Interval Syntax</a></h2>
+ <p>The <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code> and
+ <code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> directives
+ can also be defined in a more readable syntax of the form:</p>
+
+ <pre class="prettyprint lang-config">ExpiresDefault "<var>base</var> [plus <var>num</var> <var>type</var>] [<var>num</var> <var>type</var>] ..."
+ExpiresByType type/encoding "<var>base</var> [plus <var>num</var> <var>type</var>] [<var>num</var> <var>type</var>] ..."</pre>
+
+
+ <p>where <var>base</var> is one of:</p>
+
+ <ul>
+ <li><code>access</code></li>
+
+ <li><code>now</code> (equivalent to
+ '<code>access</code>')</li>
+
+ <li><code>modification</code></li>
+ </ul>
+
+ <p>The <code>plus</code> keyword is optional. <var>num</var>
+ should be an integer value [acceptable to <code>atoi()</code>],
+ and <var>type</var> is one of:</p>
+
+ <ul>
+ <li><code>years</code></li>
+ <li><code>months</code></li>
+ <li><code>weeks</code></li>
+ <li><code>days</code></li>
+ <li><code>hours</code></li>
+ <li><code>minutes</code></li>
+ <li><code>seconds</code></li>
+ </ul>
+
+ <p>For example, any of the following directives can be used to
+ make documents expire 1 month after being accessed, by
+ default:</p>
+
+ <pre class="prettyprint lang-config">ExpiresDefault "access plus 1 month"
+ExpiresDefault "access plus 4 weeks"
+ExpiresDefault "access plus 30 days"</pre>
+
+
+ <p>The expiry time can be fine-tuned by adding several
+ '<var>num</var> <var>type</var>' clauses:</p>
+
+ <pre class="prettyprint lang-config">ExpiresByType text/html "access plus 1 month 15 days 2 hours"
+ExpiresByType image/gif "modification plus 5 hours 3 minutes"</pre>
+
+
+ <p>Note that if you use a modification date based setting, the
+ Expires header will <strong>not</strong> be added to content
+ that does not come from a file on disk. This is due to the fact
+ that there is no modification time for such content.</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="ExpiresActive" id="ExpiresActive">ExpiresActive</a> <a name="expiresactive" id="expiresactive">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables generation of <code>Expires</code>
+headers</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresActive On|Off</code></td></tr>
+<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ExpiresActive Off</code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
+<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</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_expires</td></tr>
+</table>
+ <p>This directive enables or disables the generation of the
+ <code>Expires</code> and <code>Cache-Control</code> headers for
+ the document realm in question. (That is, if found in an
+ <code>.htaccess</code> file, for instance, it applies only to
+ documents generated from that directory.) If set to
+ <code>Off</code>, the headers will not be generated for any
+ document in the realm (unless overridden at a lower level, such as
+ an <code>.htaccess</code> file overriding a server config
+ file). If set to <code>On</code>, the headers will be added to
+ served documents according to the criteria defined by the
+ <code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> and
+ <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code>
+ directives (<em>q.v.</em>).</p>
+
+ <p>Note that this directive does not guarantee that an
+ <code>Expires</code> or <code>Cache-Control</code> header will be
+ generated. If the criteria aren't met, no header will be sent, and
+ the effect will be as though this directive wasn't even
+ specified.</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="ExpiresByType" id="ExpiresByType">ExpiresByType</a> <a name="expiresbytype" id="expiresbytype">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Value of the <code>Expires</code> header configured
+by MIME type</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresByType <var>MIME-type</var>
+<var>&lt;code&gt;seconds</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
+<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</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_expires</td></tr>
+</table>
+ <p>This directive defines the value of the <code>Expires</code>
+ header and the <code>max-age</code> directive of the
+ <code>Cache-Control</code> header generated for documents of the
+ specified type (<em>e.g.</em>, <code>text/html</code>). The second
+ argument sets the number of seconds that will be added to a base
+ time to construct the expiration date. The <code>Cache-Control:
+ max-age</code> is calculated by subtracting the request time from
+ the expiration date and expressing the result in seconds.</p>
+
+ <p>The base time is either the last modification time of the
+ file, or the time of the client's access to the document. Which
+ should be used is specified by the
+ <code><var>&lt;code&gt;</var></code> field; <code>M</code>
+ means that the file's last modification time should be used as
+ the base time, and <code>A</code> means the client's access
+ time should be used.</p>
+
+ <p>The difference in effect is subtle. If <code>M</code> is used,
+ all current copies of the document in all caches will expire at
+ the same time, which can be good for something like a weekly
+ notice that's always found at the same URL. If <code>A</code> is
+ used, the date of expiration is different for each client; this
+ can be good for image files that don't change very often,
+ particularly for a set of related documents that all refer to
+ the same images (<em>i.e.</em>, the images will be accessed
+ repeatedly within a relatively short timespan).</p>
+
+ <div class="example"><h3>Example:</h3><pre class="prettyprint lang-config"># enable expirations
+ExpiresActive On
+# expire GIF images after a month in the client's cache
+ExpiresByType image/gif A2592000
+# HTML documents are good for a week from the
+# time they were changed
+ExpiresByType text/html M604800</pre>
+</div>
+
+ <p>Note that this directive only has effect if
+ <code>ExpiresActive On</code> has been specified. It overrides,
+ for the specified MIME type <em>only</em>, any expiration date
+ set by the <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code>
+ directive.</p>
+
+ <p>You can also specify the expiration time calculation using
+ an <a href="#AltSyn">alternate syntax</a>, described earlier in
+ this document.</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="ExpiresDefault" id="ExpiresDefault">ExpiresDefault</a> <a name="expiresdefault" id="expiresdefault">Directive</a></h2>
+<table class="directive">
+<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Default algorithm for calculating expiration time</td></tr>
+<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresDefault <var>&lt;code&gt;seconds</var></code></td></tr>
+<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr>
+<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</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_expires</td></tr>
+</table>
+ <p>This directive sets the default algorithm for calculating the
+ expiration time for all documents in the affected realm. It can be
+ overridden on a type-by-type basis by the <code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> directive. See the
+ description of that directive for details about the syntax of the
+ argument, and the <a href="#AltSyn">alternate syntax</a>
+ description as well.</p>
+
+</div>
+</div>
+<div class="bottomlang">
+<p><span>Available Languages: </span><a href="../en/mod/mod_expires.html" title="English">&nbsp;en&nbsp;</a> |
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+<a href="../ko/mod/mod_expires.html" hreflang="ko" rel="alternate" title="Korean">&nbsp;ko&nbsp;</a></p>
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