There&#x27;s been a CPU profiler in the debugging tools for over a year, and before that there was one in the addon repository with documentation on the mozilla wiki.<p>Could be easier (like Chrome&#x27;s task manager) but it&#x27;s not as hard as you seem to think it is.<p>P.S. Chrome&#x27;s task manager isn&#x27;t accurate anymore because now a bunch of work is offloaded from the per-page processes to special catch-all processes like the &#x27;GPU Process&#x27;. So this is actually a harder problem to solve than it seems at first glance...