IIS Mod-Rewrite Standard

IIS Mod-Rewrite is a URL rewriting module for Internet Information Services (IIS). The logic of URL manipulation runs on regular expression (regex) based rules.

The configuration syntax and the behavior of IIS Mod-Rewrite engine are compatible with Apache's mod_rewrite, so that configurations from Apache can be easily migrated to IIS and vice versa. For more information about compatibility, click here.

The URL manipulation mechanism of IIS Mod-Rewrite is rule based. When a requested URL matches a rule, the corresponding text substitution will be performed on that URL.

Taking a deeper look, every rule is based on a regular expression, on which the input URL is tested. If a match occurs, then IIS Mod-Rewrite proceeds with the substitution of the URL. The substitution text consists of a combination of static and dynamic text strings. The inserted dynamic strings can be substrings of the matched URL (backreferences), server variables, or mapped values through lookup tables. This basic mechanism can be applied for a sequence of rules, using the output of one rule as the input of the next one.

A matched rule may depend on additional conditions. If those conditions are met, then the URL substitution is applied. For more about rules, conditions, regular expressions, and text substitution, see RewriteRule and RewriteCond commands.

Finally, additional features such as logging and key/value mapping functions make IIS Mod-Rewrite a powerful, feature rich, multi-purpose tool.

The rewrite configuration is a script that forms a command set. This script resides in a plain text file that can be specified by using IIS Mod-Rewrite Control Center. IIS Mod-Rewrite engine checks that configuration file every 20 seconds, and every change is automatically applied.