Ultimate Guide to htaccess and mod_rewrite

  • 5
  • July 14, 2007
Patrick Altoft

Patrick Altoft

Director of Strategy

Often described as “voodoo” by frustrated webmasters the use of mod_rewrite and htaccess files is one of the more advanced tasks a web developer has to face.

The good news is that unless you are looking for really advanced solutions you don’t have to fully understand how they work to use them on your website. Most of the htaccess and mod_rewrite tips on this page can simply be cut and pasted into a text file and uploaded to your server.

Over the last few years I’ve given the same htaccess tips to hundreds of webmasters so I decided to create a page with all the common uses.

htaccess is a configuration file that controls Apache web servers, mod_rewrite is a rewrite engine used by web servers to modify urls before they load.

The htaccess file is a text file called .htaccess – htaccess is the file extension, there is no filename. Normally it resides in the main root directory on your server but you can also create individual htaccess files for different directories on your site.

Canonicalization

The easiest htaccess trick is to make sure that your site doesn’t have any canonicalization issues on the homepage.

A lot of websites suffer from poor search engine rankings by having a number of different versions of the homepage, for example:

http://www.yoursite.com
http://yoursite.com
http://www.yoursite.com/index.html
http://yoursite.com/index.html

These pages are all seen as different urls, despite them having exactly the same content in most cases. Google has got better at deciding which version to use over the past 12 months but you can still run into problems.

To solve this issue simply add the following to your htaccess file:

Options +FollowSymLinks
RewriteEngine on
RewriteCond %{HTTP_HOST} ^yoursite.com
RewriteRule (.*) http://www.yoursite.com/$1 [R=301,L] RewriteCond %{THE_REQUEST} ^[A-Z]{3,9} /index.html HTTP/
RewriteRule ^index.html$ http://www.yoursite.com/ [R=301,L]

This will redirect all versions to http://www.yoursite.com

Changing html files to php

Sometimes you might have a static html website and need to use php code on the html pages. Rather than redirecting all your html pages to the equivalent php versions you simply need to tell your server to parse html files as if they were php.


AddHandler application/x-httpd-php .html

This works with any files so if you want to create dynamic xml or asp files that behave like php files you simply edit the code as required:


AddHandler application/x-httpd-php .xml
AddHandler application/x-httpd-php .asp

Error pages

Custom error pages can be set up in cpanel fairly easily, if you want to create a custom error page in htaccess instead use this line:


ErrorDocument 404 http://www.yoursite.com/404.php

Directory Indexes

To avoid Google indexing your directory indexes you might need to specify an index page for your directories. This is not required on some servers.


DirectoryIndex index.php3

My preference is to redirect the directory index page to either the homepage or another suitable page. For example www.yoursite.com/images/ can normally be redirected to www.yoursite.com and www.yoursite.com/forum/ can normally be redirected to www.yoursite.com/forum/index.php

Redirecting pages

A nice simple use of htaccess is to redirect one page to another:


redirect 301 /old-page.php http://www.yoursite.com/new-page.php

Sending your feed to Feedburner

If you want to switch your feed to the Feedburner service you will need to redirect your current feed to the new http://feeds.feedburner.com/yourfeed location.

The redirect needs to apply to all users except the Feedburner spider:


RewriteCond %{HTTP_USER_AGENT} !FeedBurner
RewriteRule ^your-feed.xml$ http://feeds.feedburner.com/your-feed [R,L]

Advanced hotlink protection

If you want to block other websites from hotlinking your images, but allow indexing of your images in the Google, Yahoo and MSN image search engines, you should use the code below:


RewriteEngine on
RewriteCond %{HTTP_REFERER} .
RewriteCond %{HTTP_REFERER} !^http://([^.]+.)?yoursite. [NC] RewriteCond %{HTTP_REFERER} !google. [NC] RewriteCond %{HTTP_REFERER} !search?q=cache [NC] RewriteCond %{HTTP_REFERER} !msn. [NC] RewriteCond %{HTTP_REFERER} !yahoo. [NC] RewriteCond %{REQUEST_URI} !^/hotlinker.gif$
RewriteRule .(gif|jpg|png)$ /hotlinker.gif [NC,L]

The hotlinker.gif image is a custom image that you have created. I suggest using something like “This image was hotlinked from www.yoursite.com” and your logo.

My personal preference is to allow hotlinking but to implement a solution to make use of Google Images and hotlinkers to build links to your site.

Create beautiful url’s with mod_rewrite

The Apache rewrite engine is mainly used to turn dynamic url’s such as www.yoursite.com/product.php?id=123 into static and user friendly url’s such as www.yoursite.com/product/123


RewriteEngine on
RewriteRule ^product/([^/.]+)/?$ product.php?id=$1 [L]

Another example, rewrite from:

www.yoursite.com/script.php?product=123 to www.yoursite.com/cat/product/123/


RewriteRule cat/(.*)/(.*)/$ /script.php?$1=$2

Removing query strings

Some websites like to link to you by adding an query string, for example I could link to www.yoursite.com/index.php?source=blogstorm just so you know where your traffic came from. This creates duplicate content issue for your site so you really need to redirect back to your homepage:


RewriteCond %{QUERY_STRING} ^source= RewriteRule (.*) /$1? [R=301,L]

Further reading:


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