The extension is chock full of useful features, and they work as advertised. The downside is it causes firefox to have a memory leak when viewing certain pages.

Great extension, i have just one problem, I don't know what I did to the codecs option, but I can't get 1080p for every video anymore.
Whatever option I pick between AV1/VP9/H.264, all of them, none of them, I have some videos stuck at 720p, I have to change and refresh to find the good setting, and then other videos are stuck at 720p...

Doesn't work on Android.

Almost too good to be true. But so far, it seems it is.

The main reason I wanted this extension was to make Youtube stop spamming already watched videos, random playlists and useless shorts.
1) It doesn't block already watched videos, it just makes them less visible by hiding the thumbnail and dimming their links;
2) Sometimes it marks random videos as watched, but I never even clicked their links, even less watched them;
3) It cannot block playlists, as far as I used it;
4) It blocks shorts successfully AND entirely (not just dim their links).

Great extension and much lighter than the enhance youtube extension which is also great but slows down the system. I prefer this one

On Android versions Firefox The extension does not work

Bien pour une extension, mais je recommande plutôt d'utiliser des userscripts avec TamperMonkey et assimiliés.

Very slow (even by youtube standards), whatever what the dev will say: sometimes takes almost a minute to load a youtube video, and often will fail to load the full page, with the comments.

Very buggy: again, often failing to load a page fully, the mini-player suddenly not appearing anymore when scrolling down, or among many others, the limiting to H.264 not working reliably (to be fair, it only reliably works with enhanced-h264ify, whichever main youtube extension I use). Even the menu is buggy: the search bar will always cover the link to go back in the menu (so one has to close that search bar again and again), and if used in the extension panel (as opposed to using it pinned), it won't even fit the window properly, lol!

Fortunately, I discovered a little used extension (Tweaks for youtube: only about 3k users, which is baffling), that is great where Improve youtube isn't at all. I tested them all, and that's the only one I'll keep.