it also works to downgrade Youtube videos so that you don't waste data When YouTube selects the highest resolution

Simple and perfect

It's super easy to use, and it actually works like it's supposed to. Now I just need a volume boost :)

I was tired of YouTube constantly dropping the resolution down to 480p or 720p because of its algorithms. This add-on completely solved the problem. I set my preferred resolution once, and it applies to all videos automatically. Runs smoothly in Firefox with no lag.