Meanwhile, I sit here with the firefox usage pegged at 50%, and no way to tell which tab is killing the CPU. There&#x27;s a 9-year-old bug open, requesting this feature. Now, before the fanboys jump in and say &quot;it&#x27;s open source, why don&#x27;t you do it?&quot;, I&#x27;ll admit that my hacking skillz are not enough to dive into Firefox source.