This is by far the easiest & best youtube downloader i have ever used , its so simple that well ...... even i can use it :-) . 5 Star Extension

Works

best add-on ever

gran experiencia y rapido

I was only able to download four short videos before the extension stopped working. It doesn't work for any videos; it just keeps saying, ‘Generating download link, please wait...’ Removing it and adding it back to Firefox didn't make any difference. Useless!

Does exactly what it says, and works right out of the box.
I noticed though, it wont try to download if the video was age-restricted. I only wanted the song so I just used an online converter, just something to note.

This is the best Youtube downloader I have ever used.