IISRewrite is a rule-based rewriting engine that allows a webmaster to manipulate URLs on the fly in IIS.

URLs are rewritten before IIS has handed over the request to be processed, so requests for HTML files, graphics, program files, and even entire directory structures can be rewritten before they are passed to ASP scripts for processing.

IISRewrite was written to solve some practical problems that are nearly impossible to solve with IIS and ASP. It solves the compatibility issues when doing dynamic downloads with ASP, it allows portions of dynamic sites to be indexed by search engines as if they were static HTML files, and can provide a way to customize web sites based on the client's browser type without the use of Javascript.

IISRewrite is a stripped down implementation of Apache's mod_rewrite modules for IIS. Webmasters who have used Apache's mod_rewrite in the past will find that much of the configuration and functionality is the same.

IISRewrite is compatible with Microsoft's ISAPI specification and has been tested on Windows NT Server 4.0 running IIS 4 and Windows 2000 Server running IIS 5.

IISRewrite was featured in the February 2002 edition of Microsoft's MSDN Magazine.