URL Rewriter edits URLs according to a custom regular expression when accessing a web page. It's based on the Host name rewriter extension by Mattias Lundberg.
URL Rewriter edits certain URLs, whether typed in or linked, via a set of rules before navigating to the URL. A rule consists of a regular expression specified in capture groups, a capture group number to replace, and the replacement text for that group. When you click on a link or type a URL in the address bar, it is checked against each of the rules. If a matching rule is found, the text of the specified capturing group number is replaced with the specified text.
If you click a link for
http://www.toothboiler.com/watch?v=abcdefg, it matches the regex rule and capture group 2 ("toothboiler") is replaced with "youtube" to result in