Blocks lots of things, configurable (maybe too much :p), very rewarding. The recent downvotes about additional permissions to acces IP and hostname are just bad wording on the Firefox permission popup, and there's already a Firefox bug open about this, see https://github.com/gorhill/uBlock/wiki/Permissions#access-ip-address-and-hostname-information . So plese stop downvoting this excellent softawre for no real reason.