It's disturbing that you use original developer's nickname.

Do not install this extension! This is not the original Igrigorik author! See their GitHub for confirmation.

One-starring to spread awareness that both the extension and the author of this Firefox port has no ties to the original project, as by Igrigorik's disclaimer on their Github issues page. Avoid installing/enabling since this is very suspicious behavior.

Sketchy af. The original author disavow this add-on. github.com/igrigorik/videospeed/issues/1511

I have updated the Addon to the latest version, you can find it as "Video Speed Controller Fox"

This addon also works, but for some reason, this person is not presenting himself under his real username. It's unclear why he is doing this. Why did you take a nickname that isn't yours, buddy?