I've been having this problem for almost 7 months now. Firefox stops playing videos and GIFs on random (on Youtube, Facebook etc.). All I see is just the 'buffering' icon circling. Videos start working normally again when I restart the browser (do shift+F2 -> type "restart" -> enter). But the issue comes back again usually within hours. Sometimes it even happens midway through the video - the rest of the video or any other video simply won't play until I restart the browser. One observation I've made is, around 90% of the time when this happens, 'Supports Hardware H264 Decoding' field in about:support says 'No; Too many DXVA videos playing'. I have tried the following and none of them seem to work: - Refreshing profile - Uninstall, delete profile folder, reinstall - Disable hardware acceleration - the problem was observed even while it was disabled - Update graphics card drivers to latest versions, both Intel and Nvidia Only addon I have installed is adblock plus.