Thanks for reviewing my addon! This addon actually does use event triggers! However, I debounce the events to prevent an overload of updating the badges. This way, when restoring a session or opening lots of tabs at once, the counter doesn't impact the performance of the browser. Also, I apply the badge to each tab individually (as opposed to the default of globally to all tabs and windows) so that if you have two windows on screen, both will always show the right count for their respective window.