[DiThi]

For Firefox, go to about:support and scroll down to the graphics section. Also make sure "use hardware acceleration when available" in the performance section of preferences is enabled.

For Chrome, go to chrome:gpu

For any of them, note that Windows may update the GPU driver a bit after startup and it disables GPU acceleration of open browsers until they're restarted.

[blauditore]

Thanks for the hint, though I'm facing the issue on Ubuntu only (on Windows, everything seems fine). I think I've made the same investigation before, but to no avail.

HW_COMPOSITING says "unavailable by default: Hardware compositing is disabled", and OPENGL_COMPOSITING something similar. This corresponds with my experience of jumpy scrolling and Youtube making the the fans go berserk.

But apparently, WebGL isn't affected by this and performs okay.

[DiThi]

If you use KDE, try disabling compositing with Shift+Alt+F12.

[blauditore]

I'm on Unity (and probably Gnome Shell sooner or later).