this worked amazing when i first installed it, but now its not working at all

Simple scam, that's it.
NO 4k download of 4k videos. Plus, even if you want to download anything above 720p you have to pay for the premium edition of this add-on. Which then the add-on no even works within itself but redirects you to all kind of pages.
F these Scammers, making money of the work of others

It uses a online service to do what should be done locally (look at the permissions). Furthermore it didn't work for me. The UI is good but it is an empty shell.

Downloaded the video twice, but there is no sound!
Update 2025: does not download at all!

Відео "S.T.A.L.K.E.R. 2: Серце Чорнобиля — Трейлер «Час Можливостей»" в 4к завантажило як треба, тож 5 зірок, сподіваюсь і далі так працюватиме, а головне - безкоштовно.

Links to a website, and nothing more.

That website produces a totally white screen, but does start the download. However, it doesn't say that it's doing that, and the download doesn't say how big it'll be (no percentage). This is bad hosting practice on their end.

Therefor this will get more stars if it's better integrated, gets better UI, and shows any type of progress.

does not work. mp4 downloads lead to a YouTube 404 not found page, and webm downloads lead to a mysterious and suspicious blank page.

解析用网站下线，点击按钮之后无法下载

provoque de sérieux problèmes de lecture sur certains fichier quand les tag ID3 sont modifiés, sinon très bon module

No encuentra los enlaces correctos. Y te baja la publicidad. Inútil.

Not detecting videos at all.

Doesn't appear to work properly anymore: only offering 320p and video length of 5 minutes only. Even if I go directly to youtube4kdownloader.com and paste in the video url.

very good