No doubt Firefox 50 has brought with it some nice set of new features to the table, nevertheless, it seems that at least one drawback also managed to creep in along with them as well.
When playing YouTube videos in the browser, occasionally, they may get stuck in a short loop, usually consists of the first few frames. That happens while audio playback appear to play properly.
Although most commonly noticeable on YouTube, it turns out the annoying phenomenon isn’t necessarily related to the site itself but to the HTML5 videos it plays. More accurately, it’s the way Firefox 50 handles those videos which matters.
As you’re not the only one who suffers the issue, a bug report was already submitted to Mozilla, yet even before Mozilla will come up with a new patch that fixes the issue, here’s a small step you can take right now to remedy the problem.
Fixing The Playback
First, open a new tab and type about:support in the address bar.
Look for the line that says “Multiprocess Windows” and see if it’s enabled, since you’re suffering this issue it probably isn’t: 0/1 means it isn’t.
To enable “Multiprocess Windows” you’ll need to open up another tab -> type about:config in the address bar -> search for and toggle browser.tabs.remote.autostart to true.
You may need to restart Firefox for changes to take effect.
Now, if you’re met with a disabled message appearing next to the value (of “Multiprocess Windows”), e.g. add-ons can trigger this, then you may choose one of the following options:
Either disable the add-on that causes the disabled state – this is the recommended option.
Or, force enable the state by creating a new boolean preference (in about:config) named browser.tabs.remote.force-enable and set it to true – not recommended, use it at your own risk!
What it does is it enables Firefox’s functionality, known as “Electrolysis” or “e10s”, that hosts, renders, or executes web related content in background child processes, thus splitting Firefox into multiple processes.
This helps both tighten the security of Firefox (through sandboxing) and also better the performance. As a matter of fact, Mozilla are still working to make it on by default for all users.