It works just fine most of the time. But sometimes it automatically downgrades the quality setting, and if I try to set again my desired quality, the YouTube video player begins to blink and I have to either reload that YouTube video webpage or restart the web browser.

Takes me to posts for some reason, when I click on a video

Please support - playing youtube video in background

Replicates theater mode and full screen mode from Youtube. The only useful feature is auto quality change, but takes forever to load. Doesn't work for non-SD videos.

Seems to be totally broken. Youtube loads a strange blog view that constantly jumps up and down all the time. I only wanted to stop the autoplay feature in Youtube and show videos in 1080p by default.

When I open a YouTube video link it changes the resolution (does what it proposes). But when I open the YouTube homepage, it redirects me to a random YouTube post and keeps reloading the page. So I can't use YouTube's homepage

Apparently this bug is at least one year old, deducting from old comments.

Using Firefox 77.0.1 (64-bits) at Windows 10 Pro 1909

For some reason I was not able to save any settings.

after install HD, ADs starts play on youtbe. Maybe dont coop with AdBlock.

Please fix this bug.
https://reddit.com/r/firefox/comments/aesm24/youtube_redirecting_to_a_channel/

buenas noches podre recibir notas solo en idioma español gracias

This extension does what it promises and more. It allows you to change how the description is presented, disable annotations and more.
But it has a very, very annoying but when loading YouTube's homepage. It often goes on an infinite loop, reloading the page and making it unusable. This bug is new and I had to uninstall the extension and try something else. Fix the bug and I will give you fivev stars.

Not working (anymore) :-(

Doesn't adjust quality on 60fps videos properly. I've set it to HD 1080p, but it just defaults to youtube's setting 720p60.
So that's about 50% of new videos on Youtube now.

Fr. => Dommage, très dommage... j'utilisais cette extension avec bonheur depuis plus de 2 ans et jusqu'à la v.52 de Firefox.
Je viens de faire (enfin) la mise à jour de Firefox (v.60) et Youtube High Definition ne fonctionne plus normalement (après avoir vérifié sa dernière mise à jour) d'où les 2 étoiles seulement !...
Il bloque la lecture des vidéos même en cliquant sur la fenêtre de la vidéo ou bien sur le bouton de lecture.
De plus, certaines options que j'avais déjà paramétrées ont disparues, donc impossible d'utiliser Youtube !
Ce n'est qu'en le désactivant que je peux lire les vidéos normalement.
Je viens d'installer (hélas) une autre extension qui comporte aussi beaucoup d'options et qui a l'air de très bien fonctionner.
Merci au développeur de faire une mise à jour urgente !...

Eng. => Too bad, very bad ... I used this extension with happiness for over 2 years and up to the v.52 of Firefox.
I just made (finally) the update of Firefox (v.60) and Youtube High Definition does not work normally (after checking its last update) where the 2 stars only! ...
It blocks the playback of videos even by clicking on the video window or the play button.
In addition, some options that I already set have disappeared, so impossible to use Youtube!
Only by disabling it can I play the videos normally.
I just installed (alas) another extension that also has many options and seems to work very well.
Thanks to the developer for an urgent update! ...

Won't save settings anymore and also has some UI issues (I have to scroll right to change some settings, but there is no obvious way to scroll; managed to scroll by clicking on my mouse wheel and moving the mouse sideways).