Try changing browser.privatebrowsing.forceMediaMemoryCache to true in about:config, then restart the browser and play a video in a private window.

Does it still happen with Developer Edition? Make sure you stay signed out of your sync account when testing.

I tried both:

• Private window: tried changing the setting to true, restarted browser, opened private window. No change. I switched setting back to false.
• Developer edition: installed and made sure I was signed out. If anything, the problem was worse in developer edition than in the normal edition.

Update: I muted a tab while playing YouTube, and the buffering issue vanished, which leads me to believe that this may be an audio issue. I tried updating all my audio drivers, as well as playing videos on different audio devices, and the issue did not change. I have also noticed that when I switch audio devices, the switch takes several seconds to process. This leads me to believe the issue might be with my computer after all. I will now be looking into that, and will post a solution here in case anyone else runs into this problem. That said, I'm still not ruling out that this might be a Firefox issue, since it doesn't seem to be affecting chrome (although I have started noticing a delay when I start videos on chrome, but after the video begins it works fine). Any advice anyone might have on this problem would be greatly appreciated!

Windows home or pro? If pro, try testing in Windows Sandbox (VM) and see if you have the same issue. https://www.howtogeek.com/399290/how-to-use-windows-10s-new-sandbox-to-safely-test-apps/ WiFi or plugged in? Who are you using for DNS? You can right click on the youtube video and show the stats for nerds to see you connection speed. see screenshot What security software are you running?

I have actually figured out a fix. I don't know if it will work long term, so I'll update here if it comes back. SOLUTION:

1. Opened control panel
2. Opened "hardware and sound"
3. Opened "sound"
4. Selected my current audio device (I switch between headphones and speakers) and opened "Properties"
5. Opened "advanced" tab
6. Unchecked a box marked "enable audio enhancements"

Once I did this, videos started playing normally again. I had to repeat this process for every audio device my computer is connected to, but so far it seems to have fixed it. I'm still at a complete loss as to why this affected Firefox but not chrome, but I'm just happy I've got it working again. Thanks for your help everyone!

Same issue in Firefox on a Framework 13 laptop here. YT videos play fine in Edge. A few weeks ago on my desktop PC the YT videos played just fine in Firefox. Appears many others have similar issues, see Reddit below. I do have a fair amount of Firefox extensions, haven't tried without them.

I tried both solutions above but no improvement. Is there a way to objectively quantify video playback stutter in YT other than just eyeballing it?

https://www.reddit.com/r/firefox/comments/1774nlp/everything_youtube_is_just_bad_on_firefox_how_to/

https://www.reddit.com/r/firefox/comments/18ujbm6/the_addon_h264ify_fixed_my_frame_drops_stutter_on/

https://www.reddit.com/r/firefox/comments/18oa6kt/youtube_video_stutter/

https://www.reddit.com/r/firefox/comments/194iq2o/youtube_stutters/

https://www.reddit.com/r/firefox/comments/16pl9xo/videos_started_to_stutter/ - WE MAY HAVE A WINNER! This seemed to do it for me. Some sort of DXVA issue but not sure how it relates, honestly, as it's not explained in the reddit post. media.wmf.dxva.d3d11.enabled switched from true to false.