I found HUGE (5000->500 kbp/s) download speed drop after using this. Useless. Deleted.

Restricts playback to a maximum resolution of 720p

No longer works. YouTube probably changed something yet again, and broke it. This is the problem with unmaintained add-ons, they quickly become obsolete. Sadly there are no functioning alternatives, so I'm forced by YouTube to use the AV1 codec, even though my hardware is too slow to use it without stuttering. Even setting media.av1.enabled to false has no effect any more. Mozilla seems to think that every PC user can afford 2020 hardware. At this rate, I'm just going to have to stop using YouTube, unless Google/Alphabet/Whatever wants to send me a new PC.

Not work anymore. Only sound loudness normalization disabling work.

how to make it work outside of youtube? i need it for other sites too! verypoor!

Firefox 70 x64.... doesnot work. still AVC1