My impression here from testing (in Chrome) is that when the tab for the game is not visible, the game stops its update and consumes ~0 CPU. That should be the

My impression here from testing (in Chrome) is that when the tab for the game is not visible, the game stops its update and consumes ~0 CPU. That should be the normal behaviour when running on requestAnimationFrame() and it should work on Firefox as well. Of course if you opened messenger.com in a separate browser / window then the above does not apply.