Scott Watermasysk

Still Learning to Code

Fun With ISAPI Filters

I am a big fan of ISAPI filters and ISAPI_Rewrite in particular. If you are not familiar with ISAPI filters and ISAPI_Rewrite, in a nutshell:

ISAPI_Rewrite is a powerful URL manipulation engine based on regular expressions. It acts mostly like Apache’s mod_Rewrite, but is designed specifically for Microsoft’s Internet Information Server (IIS).

For $99 a server, you cannot go wrong (although there is a nice free open source version as well.)

There are many SEO and redirect usages of the product. One of my favorites is cleaning up and simplifying urls to make them more readable and emailable.

RewriteRule /search/([a-zA-Z0-9\-\._:]*?)/ /search/?q=$1 [I,L]
RewriteRule /search/([a-zA-Z0-9\-\._:]*?)/\?p=(\d+) /search/?q=$1&p=$2 [I,L]

Using the example code above, I can now build and share search links in my blog (using Graffiti) like this: (instead of I won’t go into all of the ins and outs of ISAPI_Rewrite, but basically:

  • Declare a new rule
  • Provide a regex pattern
  • Provide a url to direct the request to (in this case the Graffiti search url)
  • (optional) Add parameters/settings