I tried a lot of extension to download videos and this one is the only who seems to work on almost all kind of videos. Added to this, you can convert directly the file in a different format, for instance a video to mp3, usefull for music and even convert local files ! Unfortunately, nowadays right protections seems more powerfull and I'm not able to download videos from TV website like "ARTE" and protected youtube videos, for which I use "youtube-dl" directly from terminal on linux.