IIS Aid

To get Drupal's Clean URL's working for you the first thing you'll need to do is head over to the Helicon Tech website and get yourself a copy of their ISAPI Rewrite product. This comes in two flavors, ISAPI Rewrite Full and ISAPI Rewrite Free. And as you may have guessed the later does not cost you a cent, but comes with some limitations over the full version. The main limitation of the free version is that it does not support site level configuration files, which if you are only running a handful of site or are running Windows XP Pro with IIS 5.1 (which can only host a single site) is perfectly fine. I have a couple of dozen sites on my server so I elected to shell out the hard earned cash for the full version.

UPDATE: This guide is for ISAPI Rewrite 2.x only! See this guide for instructions for use with ISAPI Rewrite 3.x.

Before we go on I thought I better make note that there are some differences between mod_rewrite for Apache and ISAPI Rewrite for IIS. In relation to Drupal's Clean URL feature the pertinent difference is that the mod_rewrite rules included with Drupal rely on mod_rewrites directory and file existence checking which is a feature that ISAPI Rewrite does not support. This means that you must explicitly lay down the rules for ISAPI Rewrite which makes things a little more complex, but still very doable.

Anyway, on with the show. Broken down there are three basic steps for getting Clean URL's on IIS with ISAPI Rewrite, and they are;

Step 1 - Installing and configuring ISAPI Rewrite

Download either the full or the free version of ISAPI Rewrite from the Helicon Tech website and install it as you would any normal Windows program. If you are using Windows 2003 Server with IIS 6 you will need to add some permissions manually as the IIS_WPG group willl need at least NTFS read permissions to all ISAPI_Rewrite dlls, rwhelper.dll.manifest and all httpd.ini files (modify permissions recommended on the directories containing httpd.ini files). Also if the proxy will be used (full version only) IIS_WPG should be given Modify permissions on the System temporary folder (usually C:\Windows\Temp).

Step 2 - Inserting your Drupal rewrite rules

If you are using the free version find the global httpd.ini file and open it, if you have the full version copy the global file and copy it to the root of your website. Once you have this done copy and paste the following code into the bottom of you httpd.ini file;

If your Drupal installation is in a subdirectory of your webroot, then you'll need to use the following rules;

Note: ISAPI Rewrite version 2.9 Build 63 or above is required for the above rule!

If you are using the free version and are using IIS 5 or 6 with multiple other sites that you don't wish to have the rewrite rules active on, then you'll need to specify which hostnames to exclude using the RewriteCond Host syntax. In the example below I excluded the iis-aid.com domains with the prefix of www, download and admin. All other hostnames will be rewritten.

Step 3 - Configuring settings.php

The final step is to tell Drupal to turn on Clean URL's. This is a little more complicated than it sounds as all Apache users have to do is run the Clean URL test from within their Drupal admin console and all going well they are away as soon as they select the "enable" radio button. For IIS / ISAPI Rewrite users on the other hand you must manually override the Clean URL test as even though the Clean URL test is passed the "enable" button is still not selectable. However, by setting the following directive at the bottom of the settings.php file for your site we can override this;

That should be about it. You should now have Drupal Clean URL's up and running on your IIS system using ISAPI Rewrite. Please note that while I use these very same rules myself, I do not guarantee them in any shape or form. If you have Drupal installed in a sub directory then you will need to alter the httpd.ini rules to suit. Special thanks to Hass from the Drupal forums for helping me clean up these rules. If you have any issue or comments please feel free to leave your thoughts behind.