Iridium by ParticleCore - Iridium is an extension built to improve the user experience on the new YouTube Material layout.
Video DownloadHelper - Browser extension to download videos from the Web
ImprovedTube - Allows you to improve and enhance Youtube visually or enable dozens of new features permanently or...
FastestTube - Youtube fastesttube downloader will make your internet expirience faster harder beter stronger.How to merge video and audio .
Enhancer for YouTube - Tons of features to improve your user experience on YouTube™!
FlashGot - FlashGot is a browser extension for Mozilla Firefox that is designed to make it easy to download a whole batch of files in one go. The extension is open source and free to use, but it is no longer compatible with the most recent version of Firefox.