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8 <title>When not to use mod_rewrite - Apache HTTP Server</title>
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17 <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>
18 <p class="apache">Apache HTTP Server Version 2.5</p>
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20 <div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div>
22 <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>
24 <p><span>Available Languages: </span><a href="../en/rewrite/avoid.html" title="English"> en </a></p>
28 <p>This document supplements the <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
29 <a href="../mod/mod_rewrite.html">reference documentation</a>. It describes
30 perhaps one of the most important concepts about mod_rewrite - namely,
31 when to avoid using it.</p>
33 <p>mod_rewrite should be considered a last resort, when other
34 alternatives are found wanting. Using it when there are simpler
35 alternatives leads to configurations which are confusing, fragile, and
36 hard to maintain. Understanding what other alternatives are available is
37 a very important step towards mod_rewrite mastery.</p>
39 <p>Note that many of these examples won't work unchanged in your
40 particular server configuration, so it's important that you understand
41 them, rather than merely cutting and pasting the examples into your
44 <p>The most common situation in which <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> is
45 the right tool is when the very best solution requires access to the
46 server configuration files, and you don't have that access. Some
47 configuration directives are only available in the server configuration
48 file. So if you are in a hosting situation where you only have .htaccess
49 files to work with, you may need to resort to
50 <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>.</p>
53 <div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#redirect">Simple Redirection</a></li>
54 <li><img alt="" src="../images/down.gif" /> <a href="#alias">URL Aliasing</a></li>
55 <li><img alt="" src="../images/down.gif" /> <a href="#vhosts">Virtual Hosting</a></li>
56 <li><img alt="" src="../images/down.gif" /> <a href="#proxy">Simple Proxying</a></li>
57 <li><img alt="" src="../images/down.gif" /> <a href="#setenv">Environment Variable Testing</a></li>
58 </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></ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div>
59 <div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
61 <h2><a name="redirect" id="redirect">Simple Redirection</a></h2>
64 <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
65 means to redirect one URL to another. This kind of simple redirection of
66 one URL, or a class of URLs, to somewhere else, should be accomplished
67 using these directives rather than <code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code>. <code>RedirectMatch</code>
68 allows you to include a regular expression in your redirection criteria,
69 providing many of the benefits of using <code>RewriteRule</code>.</p>
71 <p>A common use for <code>RewriteRule</code> is to redirect an entire
72 class of URLs. For example, all URLs in the <code>/one</code> directory
73 must be redirected to <code>http://one.example.com/</code>, or perhaps
74 all <code>http</code> requests must be redirected to
75 <code>https</code>.</p>
77 <p>These situations are better handled by the <code>Redirect</code>
78 directive. Remember that <code>Redirect</code> preserves path
79 information. That is to say, a redirect for a URL <code>/one</code> will
80 also redirect all URLs under that, such as <code>/one/two.html</code>
81 and <code>/one/three/four.html</code>.</p>
83 <p>To redirect URLs under <code>/one</code> to
84 <code>http://one.example.com</code>, do the following:</p>
86 <pre class="prettyprint lang-config">Redirect /one/ http://one.example.com/</pre>
89 <p>To redirect <code>http</code> URLs to <code>https</code>, do the
92 <pre class="prettyprint lang-config">
93 <VirtualHost *:80>
94 ServerName www.example.com
95 Redirect / https://www.example.com/
98 <VirtualHost *:443>
99 ServerName www.example.com
100 # ... SSL configuration goes here
101 </VirtualHost >
105 <p>The use of <code>RewriteRule</code> to perform this task may be
106 appropriate if there are other <code>RewriteRule</code> directives in
107 the same scope. This is because, when there are <code>Redirect</code>
108 and <code>RewriteRule</code> directives in the same scope, the
109 <code>RewriteRule</code> directives will run first, regardless of the
110 order of appearance in the configuration file.</p>
112 <p>In the case of the <em>http-to-https</em> redirection, the use of
113 <code>RewriteRule</code> would be appropriate if you don't have access
114 to the main server configuration file, and are obliged to perform this
115 task in a <code>.htaccess</code> file instead.</p>
117 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
118 <div class="section">
119 <h2><a name="alias" id="alias">URL Aliasing</a></h2>
120 <p>The <code class="directive"><a href="../mod/mod_alias.html#alias">Alias</a></code> directive
121 provides mapping from a URI to a directory - usually a directory outside
122 of your <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code>. Although it
123 is possible to perform this mapping with <code>mod_rewrite</code>,
124 <code>Alias</code> is the preferred method, for reasons of simplicity
127 <div class="example"><h3>Using Alias</h3><pre class="prettyprint lang-config">Alias /cats /var/www/virtualhosts/felines/htdocs</pre>
131 The use of <code>mod_rewrite</code> to perform this mapping may be
132 appropriate when you do not have access to the server configuration
133 files. Alias may only be used in server or virtualhost context, and not
134 in a <code>.htaccess</code> file.
137 <p>Symbolic links would be another way to accomplish the same thing, if
138 you have <code>Options FollowSymLinks</code> enabled on your
140 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
141 <div class="section">
142 <h2><a name="vhosts" id="vhosts">Virtual Hosting</a></h2>
143 <p>Although it is possible to handle <a href="vhosts.html">virtual hosts
144 with mod_rewrite</a>, it is seldom the right way. Creating individual
145 <VirtualHost> blocks is almost always the right way to go. In the
146 event that you have an enormous number of virtual hosts, consider using
147 <code class="module"><a href="../mod/mod_vhost_alias.html">mod_vhost_alias</a></code> to create these hosts automatically.</p>
149 <p>Third-party modules such as <a href="http://www.cri.ensmp.fr/~coelho/mod_macro/">mod_macro</a> are
150 also useful for creating a large number of virtual hosts dynamically.</p>
152 <p>Using <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> for vitualhost creation may be
153 appropriate if you are using a hosting service that does not provide
154 you access to the server configuration files, and you are therefore
155 restricted to configuration using <code>.htaccess</code> files.</p>
157 <p>See the <a href="vhosts.html">virtual hosts with mod_rewrite</a>
158 document for more details on how you might accomplish this if it still
159 seems like the right approach.</p>
161 </div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
162 <div class="section">
163 <h2><a name="proxy" id="proxy">Simple Proxying</a></h2>
165 <p><code>RewriteRule</code> provides the <a href="flags.html#flag_p">[P]</a> flag to pass rewritten URIs through
166 <code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code>.</p>
168 <pre class="prettyprint lang-config">
169 RewriteRule ^/?images(.*) http://imageserver.local/images$1 [P]
173 <p>However, in many cases, when there is no actual pattern matching
174 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.
175 The example here could be rendered as:</p>
177 <pre class="prettyprint lang-config">
178 ProxyPass /images/ http://imageserver.local/images/
182 <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
183 <code class="directive"><a href="../mod/mod_proxy.html#proxypassreverse">ProxyPassReverse</a></code> directive to
184 catch redirects issued from the back-end server:</p>
186 <pre class="prettyprint lang-config">
187 ProxyPassReverse /images/ http://imageserver.local/images/
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">
212 <If "req('Host') != 'www.example.com'">
213 Redirect / http://www.example.com/
218 <p>This technique can be used to take actions based on any request
219 header, response header, or environment variable, replacing
220 <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> in many common scenarios.</p>
222 <p>See especially the <a href="../expr.html">expression evaluation
223 documentation</a> for a overview of what types of expressions you can
224 use in <If> sections, and in certain other directives.</p>
227 <div class="bottomlang">
228 <p><span>Available Languages: </span><a href="../en/rewrite/avoid.html" title="English"> en </a></p>
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