When it works, it's great and simple! Toggle it on and the video will repeat. I do seem to have an issue with how intermittent it is. The icon does not always appear to enable repeating the video. Sometimes it's there other times not.

It stops when I restart Firefox. Every time I will need to re-enable this for being worked.

Works, but only sometimes. If you skip a track it will sometimes not realize it's supposed to be looping (even though it looks enabled) and just autoplays the next one when it gets to the end.