IIS urlrewrite: rewrite rule vs rewriteMap

Question

I have been using url rewrite for sometime and I have always and only used rules and I have always got what I need. There is also rewritemap in there. what is the difference between rewrite rule and rewritemap?

Doesn't rewrite rules map one link to another? Isn't it considered mapping?

Answer 1

A rewrite map is an arbitrary collection of name and value pairs that can be used within rewrite rules to generate a substitution URL during rewriting. Rewrite maps are particularly useful when you have a large set of rewrite rules and all of these rules use static strings (that is, when there is no pattern matching used). In those cases, instead of defining a large set of simple rewrite rules, you can put all the mappings into the rewrite map–as keys and values–between the input URL and the substitution URL. Then, to look up the substitution URL based on the input URL, you will have one rewrite rule that references this rewrite map