Works fine on YT. Was really hoping to use it on a site that has Anime and Kiss in the URL. Does not detect the video on that site :(

Does what it says on the tin. So far I have tested it on a Twitter livestream, YouTube, and ESPN+. YouTube and ESPN+ worked flawlessly, but Twitter was a little buggy; activating the plugin caused the video to pause, and the top and bottom of the video get cut off (instead of having black bars on the sides).

Annoyingly, it replaces the website's video player with Firefox's generic player, which is sometimes inferior. However, sites with good video players usually also have good theatre modes, so this add-on generally isn't necessary on those sites anyway.

I am always weary of installing relatively obscure extensions because of security concerns with trusting unknown developers. However, I have reviewed the entire source code of this addon and have found nothing suspicious, so I feel safe in recommending it.

good, but it could auto focus on player for the hotkeys to work... volume/back/forward... I have to click on the player to use hotkeys (specially for volume)

when it works, it works really good.
read as, sometimes it fails, but sends video full-window really nicely when it works.