With Flash YouTube being dead, heres how to enable hardware acceleration and get all video resolutions on YT under TFF Go into your about:config and toggle these all to true and you're set. media.mediasource.enabled media.mediasource.mp4.enabled media.mediasource.webm.enabled media.webm.enabled layers.acceleration.force-enabled --- Post Merged, Aug 4, 2017 --- Screenshot --- Post Merged, Aug 4, 2017 --- Remember to let it buffer. Probably the most important part. With these all set to true, my G5 can play back 480p html5 video fine, but clearly it's working a lot harder than playing back 720p YT under flash. I'm running a dual 1.8 with a GeForce 6800GT. I'd hate to say it, but if you have a lower end or just slow G4, YouTube's website may now be out of the question for you.