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10 <title>When not to use mod_rewrite - Apache HTTP Server Version 2.5</title>
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20 <p class="apache">Apache HTTP Server Version 2.5</p>
21 <img alt="" src="../images/feather.png" /></div>
22 <div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
24 <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 2.5</a> > <a href="./">Rewrite</a></div><div id="page-content"><div id="preamble"><h1>When not to use mod_rewrite</h1>
26 <p><span>Available Languages: </span><a href="../en/rewrite/avoid.html" title="English"> en </a></p>
30 <p>This document supplements the <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
31 <a href="../mod/mod_rewrite.html">reference documentation</a>. It describes
32 perhaps one of the most important concepts about <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> - namely,
33 when to avoid using it.</p>
35 <p><code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> should be considered a last resort, when other
36 alternatives are found wanting. Using it when there are simpler
37 alternatives leads to configurations which are confusing, fragile, and
38 hard to maintain. Understanding what other alternatives are available is
39 a very important step towards <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> mastery.</p>
41 <p>Note that many of these examples won't work unchanged in your
42 particular server configuration, so it's important that you understand
43 them, rather than merely cutting and pasting the examples into your
46 <p>The most common situation in which <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> is
47 the right tool is when the very best solution requires access to the
48 server configuration files, and you don't have that access. Some
49 configuration directives are only available in the server configuration
50 file. So if you are in a hosting situation where you only have .htaccess
51 files to work with, you may need to resort to
52 <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>.</p>
55 <div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#redirect">Simple Redirection</a></li>
56 <li><img alt="" src="../images/down.gif" /> <a href="#alias">URL Aliasing</a></li>
57 <li><img alt="" src="../images/down.gif" /> <a href="#vhosts">Virtual Hosting</a></li>
58 <li><img alt="" src="../images/down.gif" /> <a href="#proxy">Simple Proxying</a></li>
59 <li><img alt="" src="../images/down.gif" /> <a href="#setenv">Environment Variable Testing</a></li>
60 </ul><h3>See also</h3><ul class="seealso"><li><a href="../mod/mod_rewrite.html">Module documentation</a></li><li><a href="intro.html">mod_rewrite introduction</a></li><li><a href="remapping.html">Redirection and remapping</a></li><li><a href="access.html">Controlling access</a></li><li><a href="vhosts.html">Virtual hosts</a></li><li><a href="proxy.html">Proxying</a></li><li><a href="rewritemap.html">Using RewriteMap</a></li><li><a href="advanced.html">Advanced techniques</a></li><li><a href="#comments_section">Comments</a></li></ul></div>
61 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
63 <h2><a name="redirect" id="redirect">Simple Redirection</a></h2>
66 <p><code class="module"><a href="../mod/mod_alias.html">mod_alias</a></code> provides the <code class="directive"><a href="../mod/mod_alias.html#redirect">Redirect</a></code> and <code class="directive"><a href="../mod/mod_alias.html#redirectmatch">RedirectMatch</a></code> directives, which provide a
67 means to redirect one URL to another. This kind of simple redirection of
68 one URL, or a class of URLs, to somewhere else, should be accomplished
69 using these directives rather than <code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code>. <code>RedirectMatch</code>
70 allows you to include a regular expression in your redirection criteria,
71 providing many of the benefits of using <code>RewriteRule</code>.</p>
73 <p>A common use for <code>RewriteRule</code> is to redirect an entire
74 class of URLs. For example, all URLs in the <code>/one</code> directory
75 must be redirected to <code>http://one.example.com/</code>, or perhaps
76 all <code>http</code> requests must be redirected to
77 <code>https</code>.</p>
79 <p>These situations are better handled by the <code>Redirect</code>
80 directive. Remember that <code>Redirect</code> preserves path
81 information. That is to say, a redirect for a URL <code>/one</code> will
82 also redirect all URLs under that, such as <code>/one/two.html</code>
83 and <code>/one/three/four.html</code>.</p>
85 <p>To redirect URLs under <code>/one</code> to
86 <code>http://one.example.com</code>, do the following:</p>
88 <pre class="prettyprint lang-config">Redirect "/one/" "http://one.example.com/"</pre>
91 <p>To redirect one hostname to another, for example
92 <code>example.com</code> to <code>www.example.com</code>, see the
93 <a href="remapping.html#canonicalhost">Canonical Hostnames</a>
96 <p>To redirect <code>http</code> URLs to <code>https</code>, do the
99 <pre class="prettyprint lang-config"><VirtualHost *:80>
100 ServerName www.example.com
101 Redirect "/" "https://www.example.com/"
104 <VirtualHost *:443>
105 ServerName www.example.com
106 # ... SSL configuration goes here
107 </VirtualHost></pre>
110 <p>The use of <code>RewriteRule</code> to perform this task may be
111 appropriate if there are other <code>RewriteRule</code> directives in
112 the same scope. This is because, when there are <code>Redirect</code>
113 and <code>RewriteRule</code> directives in the same scope, the
114 <code>RewriteRule</code> directives will run first, regardless of the
115 order of appearance in the configuration file.</p>
117 <p>In the case of the <em>http-to-https</em> redirection, the use of
118 <code>RewriteRule</code> would be appropriate if you don't have access
119 to the main server configuration file, and are obliged to perform this
120 task in a <code>.htaccess</code> file instead.</p>
122 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
123 <div class="section">
124 <h2><a name="alias" id="alias">URL Aliasing</a></h2>
125 <p>The <code class="directive"><a href="../mod/mod_alias.html#alias">Alias</a></code> directive
126 provides mapping from a URI to a directory - usually a directory outside
127 of your <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code>. Although it
128 is possible to perform this mapping with <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>,
129 <code class="directive"><a href="../mod/mod_alias.html#alias">Alias</a></code> is the preferred method, for
130 reasons of simplicity and performance.</p>
132 <div class="example"><h3>Using Alias</h3><pre class="prettyprint lang-config">Alias "/cats" "/var/www/virtualhosts/felines/htdocs"</pre>
136 The use of <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> to perform this mapping may be
137 appropriate when you do not have access to the server configuration
138 files. Alias may only be used in server or virtualhost context, and not
139 in a <code>.htaccess</code> file.
142 <p>Symbolic links would be another way to accomplish the same thing, if
143 you have <code>Options FollowSymLinks</code> enabled on your
145 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
146 <div class="section">
147 <h2><a name="vhosts" id="vhosts">Virtual Hosting</a></h2>
148 <p>Although it is possible to handle <a href="vhosts.html">virtual hosts
149 with mod_rewrite</a>, it is seldom the right way. Creating individual
150 <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code> blocks is
151 almost always the right way to go. In the
152 event that you have an enormous number of virtual hosts, consider using
153 <code class="module"><a href="../mod/mod_vhost_alias.html">mod_vhost_alias</a></code> to create these hosts automatically.</p>
155 <p>Modules such as <code class="module"><a href="../mod/mod_macro.html">mod_macro</a></code> are
156 also useful for creating a large number of virtual hosts dynamically.</p>
158 <p>Using <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> for vitualhost creation may be
159 appropriate if you are using a hosting service that does not provide
160 you access to the server configuration files, and you are therefore
161 restricted to configuration using <code>.htaccess</code> files.</p>
163 <p>See the <a href="vhosts.html">virtual hosts with mod_rewrite</a>
164 document for more details on how you might accomplish this if it still
165 seems like the right approach.</p>
167 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
168 <div class="section">
169 <h2><a name="proxy" id="proxy">Simple Proxying</a></h2>
171 <p><code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code> provides the <a href="flags.html#flag_p">[P]</a> flag to pass rewritten URIs through
172 <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code>.</p>
174 <pre class="prettyprint lang-config">RewriteRule "^/?images(.*)" "http://imageserver.local/images$1" [P]</pre>
177 <p>However, in many cases, when there is no actual pattern matching
178 needed, as in the example shown above, the <code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code> directive is a better choice.
179 The example here could be rendered as:</p>
181 <pre class="prettyprint lang-config">ProxyPass "/images/" "http://imageserver.local/images/"</pre>
184 <p>Note that whether you use <code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code> or <code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code>, you'll still need to use the
185 <code class="directive"><a href="../mod/mod_proxy.html#proxypassreverse">ProxyPassReverse</a></code> directive to
186 catch redirects issued from the back-end server:</p>
188 <pre class="prettyprint lang-config">ProxyPassReverse "/images/" "http://imageserver.local/images/"</pre>
191 <p>You may need to use <code>RewriteRule</code> instead when there are
192 other <code>RewriteRule</code>s in effect in the same scope, as a
193 <code>RewriteRule</code> will usually take effect before a
194 <code>ProxyPass</code>, and so may preempt what you're trying to
197 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
198 <div class="section">
199 <h2><a name="setenv" id="setenv">Environment Variable Testing</a></h2>
201 <p><code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> is frequently used to take a particular
202 action based on the presence or absence of a particular environment
203 variable or request header. This can be done more efficiently using the
204 <code class="directive"><a href="../mod/core.html#if"><If></a></code>.</p>
206 <p>Consider, for example, the common scenario where
207 <code class="directive">RewriteRule</code> is used to enforce a canonical
208 hostname, such as <code>www.example.com</code> instead of
209 <code>example.com</code>. This can be done using the <code class="directive"><a href="../mod/core.html#if"><If></a></code> directive, as shown here:</p>
211 <pre class="prettyprint lang-config"><If "req('Host') != 'www.example.com'">
212 Redirect "/" "http://www.example.com/"
216 <p>This technique can be used to take actions based on any request
217 header, response header, or environment variable, replacing
218 <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> in many common scenarios.</p>
220 <p>See especially the <a href="../expr.html">expression evaluation
221 documentation</a> for a overview of what types of expressions you can
222 use in <code class="directive"><a href="../mod/core.html#if"><If></a></code> sections,
223 and in certain other directives.</p>
226 <div class="bottomlang">
227 <p><span>Available Languages: </span><a href="../en/rewrite/avoid.html" title="English"> en </a></p>
228 </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. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our <a href="http://httpd.apache.org/lists.html">mailing lists</a>.</div>
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