YouTube High Definition is a powerful tool that will let you automatically play all YouTube videos in HD (High Definition), turn off annotations, change video player size, auto stop videos, auto mute videos, control embedded videos and much more.
Play YouTube™ Videos in Flash or HTML5 Player
Enlarge thumbnails, and show images/videos from links with a mouse hover.
Removes all annoying Ads from YouTube
Tons of features to improve your user experience on YouTube™.
瞬间过滤B站(bilibili.com)刷屏的相似弹幕，还你清爽的弹幕视频体验。 *a tweak for a Chinese website. Please ignore this add-on if you are not a user of bilibili.com.*
Reverse image search using various search engines, such as Google, Bing, Yandex, Baidu and TinEye.
The entire page will be fading to dark, so you can watch the videos as if you were in the cinema. Works for YouTube™ and Beyond. It works for all known video sites such as YouTube, Vimeo, Twitch, Dailymotion, Facebook, Hulu, Metacafe, YouKu, etc.
Listen to live radio stations from around the world!
Save the things you find on the Web to Pinterest.
Download every YouTube video you want and you can download them as MP4, WEBM, 3GP formats. Easy & Fast!
One Click to download any video from Youtube. Compatible with new FireFox Quantum 57+