Hi I recently had this problem, when i open a video (to listen to music) and open another tab to watch some gifs, the video bug multiple time for a brief delay but is little bit annoying, i never had this problem before, i made some research and followed some steps.. i couldn't resolve the problem: - cleared the cache - refresh the page - launch Firefox on ''Save Mode'' - Force youtube to use H.264 _ installed this add-ons : https://support.mozilla.org/en-US/questions/1245735 - reduced the performance (use less memory/cores) _ disable hardware acceleration. Cheers