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<?xml version="1.0" encoding="ISO-8859-1"?>
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<title>When not to use mod_rewrite - Apache HTTP Server</title>
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<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="../faq/">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p>
<p class="apache">Apache HTTP Server Version 2.5</p>
<img alt="" src="../images/feather.gif" /></div>
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<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>
<div class="toplang">
<p><span>Available Languages: </span><a href="../en/rewrite/avoid.html" title="English"> en </a></p>
</div>
<p>This document supplements the <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>
<a href="../mod/mod_rewrite.html">reference documentation</a>. It describes
perhaps one of the most important concepts about mod_rewrite - namely,
when to avoid using it.</p>
<p>mod_rewrite should be considered a last resort, when other
alternatives are found wanting. Using it when there are simpler
alternatives leads to configurations which are confusing, fragile, and
hard to maintain. Understanding what other alternatives are available is
a very important step towards mod_rewrite mastery.</p>
<p>Note that many of these examples won't work unchanged in your
particular server configuration, so it's important that you understand
them, rather than merely cutting and pasting the examples into your
configuration.</p>
<p>The most common situation in which <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> is
the right tool is when the very best solution requires access to the
server configuration files, and you don't have that access. Some
configuration directives are only available in the server configuration
file. So if you are in a hosting situation where you only have .htaccess
files to work with, you may need to resort to
<code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code>.</p>
</div>
<div id="quickview"><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#redirect">Simple Redirection</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#alias">URL Aliasing</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#vhosts">Virtual Hosting</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#proxy">Simple Proxying</a></li>
<li><img alt="" src="../images/down.gif" /> <a href="#setenv">Environment Variable Testing</a></li>
</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></div>
<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="redirect" id="redirect">Simple Redirection</a></h2>
<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
means to redirect one URL to another. This kind of simple redirection of
one URL, or a class of URLs, to somewhere else, should be accomplished
using these directives rather than <code class="directive"><a href="../mod/mod_rewrite.html#rewriterule">RewriteRule</a></code>. <code>RedirectMatch</code>
allows you to include a regular expression in your redirection criteria,
providing many of the benefits of using <code>RewriteRule</code>.</p>
<p>A common use for <code>RewriteRule</code> is to redirect an entire
class of URLs. For example, all URLs in the <code>/one</code> directory
must be redirected to <code>http://one.example.com/</code>, or perhaps
all <code>http</code> requests must be redirected to
<code>https</code>.</p>
<p>These situations are better handled by the <code>Redirect</code>
directive. Remember that <code>Redirect</code> preserves path
information. That is to say, a redirect for a URL <code>/one</code> will
also redirect all URLs under that, such as <code>/one/two.html</code>
and <code>/one/three/four.html</code>.</p>
<p>To redirect URLs under <code>/one</code> to
<code>http://one.example.com</code>, do the following:</p>
<div class="example"><p><code>
Redirect /one/ http://one.example.com/
</code></p></div>
<p>To redirect <code>http</code> URLs to <code>https</code>, do the
following:</p>
<div class="example"><p><code>
<VirtualHost *:80>
ServerName www.example.com<br />
Redirect / https://www.example.com/<br />
</VirtualHost >
<br />
<VirtualHost *:443>
ServerName www.example.com<br />
<br />
# ... SSL configuration goes here<br />
</VirtualHost >
</code></p></div>
<p>The use of <code>RewriteRule</code> to perform this task may be
appropriate if there are other <code>RewriteRule</code> directives in
the same scope. This is because, when there are <code>Redirect</code>
and <code>RewriteRule</code> directives in the same scope, the
<code>RewriteRule</code> directives will run first, regardless of the
order of appearance in the configuration file.</p>
<p>In the case of the <em>http-to-https</em> redirection, the use of
<code>RewriteRule</code> would be appropriate if you don't have access
to the main server configuration file, and are obliged to perform this
task in a <code>.htaccess</code> file instead.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="alias" id="alias">URL Aliasing</a></h2>
<p>The <code class="directive"><a href="../mod/mod_alias.html#alias">Alias</a></code> directive
provides mapping from a URI to a directory - usually a directory outside
of your <code class="directive"><a href="../mod/core.html#documentroot">DocumentRoot</a></code>. Although it
is possible to perform this mapping with <code>mod_rewrite</code>,
<code>Alias</code> is the preferred method, for reasons of simplicity
and performance.</p>
<div class="example"><h3>Using Alias</h3><p><code>
Alias /cats /var/www/virtualhosts/felines/htdocs
</code></p></div>
<p>
The use of <code>mod_rewrite</code> to perform this mapping may be
appropriate when you do not have access to the server configuration
files. Alias may only be used in server or virtualhost context, and not
in a <code>.htaccess</code> file.
</p>
<p>Symbolic links would be another way to accomplish the same thing, if
you have <code>Options FollowSymLinks</code> enabled on your
server.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="vhosts" id="vhosts">Virtual Hosting</a></h2>
<p>Although it is possible to handle <a href="vhosts.html">virtual hosts
with mod_rewrite</a>, it is seldom the right way. Creating individual
<VirtualHost> blocks is almost always the right way to go. In the
event that you have an enormous number of virtual hosts, consider using
<code class="module"><a href="../mod/mod_vhost_alias.html">mod_vhost_alias</a></code> to create these hosts automatically.</p>
<p>Third-party modules such as <a href="http://www.cri.ensmp.fr/~coelho/mod_macro/">mod_macro</a> are
also useful for creating a large number of virtual hosts dynamically.</p>
<p>Using <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> for vitualhost creation may be
appropriate if you are using a hosting service that does not provide
you access to the server configuration files, and you are therefore
restricted to configuration using <code>.htaccess</code> files.</p>
<p>See the <a href="vhosts.html">virtual hosts with mod_rewrite</a>
document for more details on how you might accomplish this if it still
seems like the right approach.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="proxy" id="proxy">Simple Proxying</a></h2>
<p><code>RewriteRule</code> provides the <a href="flags.html#flag_p">[P]</a> flag to pass rewritten URIs through
<code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code>.</p>
<div class="example"><p><code>
RewriteRule ^/?images(.*) http://imageserver.local/images$1 [P]
</code></p></div>
<p>However, in many cases, when there is no actual pattern matching
meeded, 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.
The example here could be rendered as:</p>
<div class="example"><p><code>
ProxyPass /images/ http://imageserver.local/images/
</code></p></div>
<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
<code class="directive"><a href="../mod/mod_proxy.html#proxypassreverse">ProxyPassReverse</a></code> directive to
catch redirects issued from the back-end server:</p>
<div class="example"><p><code>
ProxyPassReverse /images/ http://imageserver.local/images/
</code></p></div>
<p>You may need to use <code>RewriteRule</code> instead when there are
other <code>RewriteRule</code>s in effect in the same scope, as a
<code>RewriteRule</code> will usually take effect before a
<code>ProxyPass</code>, and so may preempt what you're trying to
accomplish.</p>
</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div>
<div class="section">
<h2><a name="setenv" id="setenv">Environment Variable Testing</a></h2>
<p><code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> is frequently used to take a particular
action based on the presence or absense of a particular environment
variable or request header. This can be done more efficiently using the
<code class="directive"><a href="../mod/core.html#if"><If></a></code>.</p>
<p>Consider, for example, the common scenario where
<code class="directive">RewriteRule</code> is used to enforce a canonical
hostname, such as <code>www.example.com</code> instead of
<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>
<div class="example"><p><code>
<If "$req{Host} != 'www.example.com'"><br />
RedirectMatch (.*) http://www.example.com$1<br />
</If>
</code></p></div>
<p>This technique can be used to take actions based on any request
header, response header, or environment variable, replacing
<code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> in many common scenarios.</p>
<p>See especially the <a href="../expr.html">expression evaluation
documentation</a> for a overview of what types of expressions you can
use in <If> sections, and in certain other directives.</p>
</div></div>
<div class="bottomlang">
<p><span>Available Languages: </span><a href="../en/rewrite/avoid.html" title="English"> en </a></p>
</div><div id="footer">
<p class="apache">Copyright 2012 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p>
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