Firefox has had it native since firefox 4. See this article: http://kb.mozillazine.org/Location_Bar_search#Location_Bar_search_.28internal_-_Auto_Complete.29 ht

Firefox has had it native since firefox 4. See this article: http://kb.mozillazine.org/Location_Bar_search#Location_Bar_search_.28internal_-_Auto_Complete.29 http://kb.mozillazine.org/Location_Bar_search#Location_Bar_s... You can enter "% string" into the location bar, and it will suggest switches to open tabs which contain that string either in their title or URL. I've been using this little-known location bar feature for a long long time.