I had to disable it since it was causing serious issues to some websites that had nothing to do with youtube. The developer kindly replied saying the issues would be addressed, but I wonder if I can now trust it won't do the same again, with some other website/web app.
EDIT May 2022: still causing issues, and preventing checkout via PayPal to work at all. Such a pity I have to delete this extension permanently because it's a real disaster.

essential addon for any browsing which uses videos

I can’t use it..why?

I absolutely love it, thank you!!! Just remembering my speed setting would be enough and here I can control it with shortcuts, najssssss... Where's the "donate" button?

Работает скорость клавишами регулируется

Please support firefox preview :D

Most comprehensive version of this tool I've found. Great stuff.

Very good extension