Currently every request from the browser occurs an overhead that is O(N) where N is the number of rules (or rulesets with match_rules). This is not good enough, especially if we intend to include all the rules people are submitting. O(1) lookups should be possible. One way is a dictionary of target domains, with lookups looking something like this: If the request is for content at blah.thing.com, we look up *.thing.com, thing.*.com, blah.thing.* in the dictionary. For the time being, rulesets should be able to signal what domains they target in at least that level of specificity Eg, Google.xml targets: google.* www.google.* google.com.* www.google.com.* google.co.* www.google.co.* BUT, if we ever had to worry about *.google.* this wouldn't be enough...