1<?xml version="1.0" encoding="ISO-8859-1"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!-- 4 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 5 This file is generated from xml source: DO NOT EDIT 6 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 7 --> 8<title>mod_expires - Apache HTTP Server</title> 9<link href="/style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> 10<link href="/style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> 11<link href="/style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="/style/css/prettify.css" /> 12<script src="/style/scripts/prettify.js" type="text/javascript"> 13</script> 14 15<link href="/images/favicon.ico" rel="shortcut icon" /></head> 16<body> 17<div id="page-header"> 18<p class="menu"><a href="/mod/">Modules</a> | <a href="/mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="/glossary.html">Glossary</a> | <a href="/sitemap.html">Sitemap</a></p> 19<p class="apache">Apache HTTP Server Version 2.2</p> 20<img alt="" src="/images/feather.gif" /></div> 21<div class="up"><a href="./"><img title="<-" alt="<-" src="/images/left.gif" /></a></div> 22<div id="path"> 23<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.2</a> > <a href="./">Modules</a></div> 24<div id="page-content"> 25<div id="preamble"><h1>Apache Module mod_expires</h1> 26<div class="toplang"> 27<p><span>Available Languages: </span><a href="/en/mod/mod_expires.html" title="English"> en </a> | 28<a href="/ja/mod/mod_expires.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | 29<a href="/ko/mod/mod_expires.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p> 30</div> 31<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Generation of <code>Expires</code> and 32<code>Cache-Control</code> HTTP headers according to user-specified 33criteria</td></tr> 34<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr> 35<tr><th><a href="module-dict.html#ModuleIdentifier">Module�Identifier:</a></th><td>expires_module</td></tr> 36<tr><th><a href="module-dict.html#SourceFile">Source�File:</a></th><td>mod_expires.c</td></tr></table> 37<h3>Summary</h3> 38 39 <p>This module controls the setting of the <code>Expires</code> 40 HTTP header and the <code>max-age</code> directive of the 41 <code>Cache-Control</code> HTTP header in server responses. The 42 expiration date can set to be relative to either the time the 43 source file was last modified, or to the time of the client 44 access.</p> 45 46 <p>These HTTP headers are an instruction to the client about the 47 document's validity and persistence. If cached, the document may 48 be fetched from the cache rather than from the source until this 49 time has passed. After that, the cache copy is considered 50 "expired" and invalid, and a new copy must be obtained from the 51 source.</p> 52 53 <p>To modify <code>Cache-Control</code> directives other than 54 <code>max-age</code> (see <a href="http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.9">RFC 55 2616 section 14.9</a>), you can use the <code class="directive"><a href="/mod/mod_headers.html#header">Header</a></code> directive.</p> 56 57 <p> When the <code>Expires</code> header is already part of the response 58 generated by the server, for example when generated by a CGI script or 59 proxied from an origin server, this module does not change or add 60 an <code>Expires</code> or <code>Cache-Control</code> header.</p> 61</div> 62<div id="quickview"><h3 class="directives">Directives</h3> 63<ul id="toc"> 64<li><img alt="" src="/images/down.gif" /> <a href="#expiresactive">ExpiresActive</a></li> 65<li><img alt="" src="/images/down.gif" /> <a href="#expiresbytype">ExpiresByType</a></li> 66<li><img alt="" src="/images/down.gif" /> <a href="#expiresdefault">ExpiresDefault</a></li> 67</ul> 68<h3>Topics</h3> 69<ul id="topics"> 70<li><img alt="" src="/images/down.gif" /> <a href="#AltSyn">Alternate Interval Syntax</a></li> 71</ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div> 72<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 73<div class="section"> 74<h2><a name="AltSyn" id="AltSyn">Alternate Interval Syntax</a></h2> 75 <p>The <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code> and 76 <code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> directives 77 can also be defined in a more readable syntax of the form:</p> 78 79 <div class="example"><p><code> 80 ExpiresDefault "<var>base</var> [plus <var>num</var> <var>type</var>] 81 [<var>num</var> <var>type</var>] ..."<br /> 82 ExpiresByType type/encoding "<var>base</var> [plus <var>num</var> <var>type</var>] 83 [<var>num</var> <var>type</var>] ..." 84 </code></p></div> 85 86 <p>where <var>base</var> is one of:</p> 87 88 <ul> 89 <li><code>access</code></li> 90 91 <li><code>now</code> (equivalent to 92 '<code>access</code>')</li> 93 94 <li><code>modification</code></li> 95 </ul> 96 97 <p>The <code>plus</code> keyword is optional. <var>num</var> 98 should be an integer value [acceptable to <code>atoi()</code>], 99 and <var>type</var> is one of:</p> 100 101 <ul> 102 <li><code>years</code></li> 103 <li><code>months</code></li> 104 <li><code>weeks</code></li> 105 <li><code>days</code></li> 106 <li><code>hours</code></li> 107 <li><code>minutes</code></li> 108 <li><code>seconds</code></li> 109 </ul> 110 111 <p>For example, any of the following directives can be used to 112 make documents expire 1 month after being accessed, by 113 default:</p> 114 115 <div class="example"><p><code> 116 ExpiresDefault "access plus 1 month"<br /> 117 ExpiresDefault "access plus 4 weeks"<br /> 118 ExpiresDefault "access plus 30 days" 119 </code></p></div> 120 121 <p>The expiry time can be fine-tuned by adding several 122 '<var>num</var> <var>type</var>' clauses:</p> 123 124 <div class="example"><p><code> 125 ExpiresByType text/html "access plus 1 month 15 126 days 2 hours"<br /> 127 ExpiresByType image/gif "modification plus 5 hours 3 128 minutes" 129 </code></p></div> 130 131 <p>Note that if you use a modification date based setting, the 132 Expires header will <strong>not</strong> be added to content 133 that does not come from a file on disk. This is due to the fact 134 that there is no modification time for such content.</p> 135</div> 136<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 137<div class="directive-section"><h2><a name="ExpiresActive" id="ExpiresActive">ExpiresActive</a> <a name="expiresactive" id="expiresactive">Directive</a></h2> 138<table class="directive"> 139<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Enables generation of <code>Expires</code> 140headers</td></tr> 141<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresActive On|Off</code></td></tr> 142<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr> 143<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</td></tr> 144<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> 145<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_expires</td></tr> 146</table> 147 <p>This directive enables or disables the generation of the 148 <code>Expires</code> and <code>Cache-Control</code> headers for 149 the document realm in question. (That is, if found in an 150 <code>.htaccess</code> file, for instance, it applies only to 151 documents generated from that directory.) If set to 152 <code>Off</code>, the headers will not be generated for any 153 document in the realm (unless overridden at a lower level, such as 154 an <code>.htaccess</code> file overriding a server config 155 file). If set to <code>On</code>, the headers will be added to 156 served documents according to the criteria defined by the 157 <code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> and 158 <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code> 159 directives (<em>q.v.</em>).</p> 160 161 <p>Note that this directive does not guarantee that an 162 <code>Expires</code> or <code>Cache-Control</code> header will be 163 generated. If the criteria aren't met, no header will be sent, and 164 the effect will be as though this directive wasn't even 165 specified.</p> 166 167</div> 168<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 169<div class="directive-section"><h2><a name="ExpiresByType" id="ExpiresByType">ExpiresByType</a> <a name="expiresbytype" id="expiresbytype">Directive</a></h2> 170<table class="directive"> 171<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Value of the <code>Expires</code> header configured 172by MIME type</td></tr> 173<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresByType <var>MIME-type</var> 174<var><code>seconds</var></code></td></tr> 175<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr> 176<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</td></tr> 177<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> 178<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_expires</td></tr> 179</table> 180 <p>This directive defines the value of the <code>Expires</code> 181 header and the <code>max-age</code> directive of the 182 <code>Cache-Control</code> header generated for documents of the 183 specified type (<em>e.g.</em>, <code>text/html</code>). The second 184 argument sets the number of seconds that will be added to a base 185 time to construct the expiration date. The <code>Cache-Control: 186 max-age</code> is calculated by subtracting the request time from 187 the expiration date and expressing the result in seconds.</p> 188 189 <p>The base time is either the last modification time of the 190 file, or the time of the client's access to the document. Which 191 should be used is specified by the 192 <code><var><code></var></code> field; <code>M</code> 193 means that the file's last modification time should be used as 194 the base time, and <code>A</code> means the client's access 195 time should be used.</p> 196 197 <p>The difference in effect is subtle. If <code>M</code> is used, 198 all current copies of the document in all caches will expire at 199 the same time, which can be good for something like a weekly 200 notice that's always found at the same URL. If <code>A</code> is 201 used, the date of expiration is different for each client; this 202 can be good for image files that don't change very often, 203 particularly for a set of related documents that all refer to 204 the same images (<em>i.e.</em>, the images will be accessed 205 repeatedly within a relatively short timespan).</p> 206 207 <div class="example"><h3>Example:</h3><p><code> 208 # enable expirations<br /> 209 ExpiresActive On<br /> 210 # expire GIF images after a month in the client's cache<br /> 211 ExpiresByType image/gif A2592000<br /> 212 # HTML documents are good for a week from the<br /> 213 # time they were changed<br /> 214 ExpiresByType text/html M604800 215 </code></p></div> 216 217 <p>Note that this directive only has effect if 218 <code>ExpiresActive On</code> has been specified. It overrides, 219 for the specified MIME type <em>only</em>, any expiration date 220 set by the <code class="directive"><a href="#expiresdefault">ExpiresDefault</a></code> 221 directive.</p> 222 223 <p>You can also specify the expiration time calculation using 224 an <a href="#AltSyn">alternate syntax</a>, described earlier in 225 this document.</p> 226 227</div> 228<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 229<div class="directive-section"><h2><a name="ExpiresDefault" id="ExpiresDefault">ExpiresDefault</a> <a name="expiresdefault" id="expiresdefault">Directive</a></h2> 230<table class="directive"> 231<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Default algorithm for calculating expiration time</td></tr> 232<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ExpiresDefault <var><code>seconds</var></code></td></tr> 233<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host, directory, .htaccess</td></tr> 234<tr><th><a href="directive-dict.html#Override">Override:</a></th><td>Indexes</td></tr> 235<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> 236<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_expires</td></tr> 237</table> 238 <p>This directive sets the default algorithm for calculating the 239 expiration time for all documents in the affected realm. It can be 240 overridden on a type-by-type basis by the <code class="directive"><a href="#expiresbytype">ExpiresByType</a></code> directive. See the 241 description of that directive for details about the syntax of the 242 argument, and the <a href="#AltSyn">alternate syntax</a> 243 description as well.</p> 244 245</div> 246</div> 247<div class="bottomlang"> 248<p><span>Available Languages: </span><a href="/en/mod/mod_expires.html" title="English"> en </a> | 249<a href="/ja/mod/mod_expires.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | 250<a href="/ko/mod/mod_expires.html" hreflang="ko" rel="alternate" title="Korean"> ko </a></p> 251</div><div class="top"><a href="#page-header"><img src="/images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&A section. 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