I use Firefox to watch movies on YouTube, Netflix, and many other sites. I always make these movies full screen. Usually, that means that my computer will stay awake while the movie plays. But after 4 years of this working without issue, I started having problems last November. Since then, whenever I make videos fullscreen, they'll display as normal, but after a few minutes, my computer's screensaver will come on. It's like my computer can't recognize that the videos are fullscreen. It treats them as regular videos and kicks into whatever power management settings I've set up I've tried disabling all my add-ons. I've tried changing all my power settings. (Whatever power setting I choose, that's what ends up happening: screensaver at 10 min, 15 min, etc.) But nothing I do can get my computer to recognize fullscreen videos from Firefox . This only happens with Firefox. When I play full screen videos in VLC, my computer does not go into screensaver/sleep/etc. I'm running Firefox 123.0 on Linux Lite (Ubuntu). The only way I get this to work-- and it doesn't always work-- is if I restart my computer, Firefox will sometimes behave as expected. But if I finish a movie and let my computer go to sleep, then the next time it wakes, I'll have the same problem again. All help appreciated. Thank you!