Simple and without the need to give risky permissions. All those extensions requiring to get all your data just to download an mp3 are suspicious to say the least. I found this solution simple, of course the ads are annoying, but worth the service.

Круто, работает, в отличие от аналогов!

It works to download MP3 or MP4 from youtube easily for me.

Finally I found an mozilla addon which really works to download MP3 or MP4 from youtube easily, this is an excellent addon.

It works perfectly.

Install the addon
go to youtube & find video
click on the cube in top right corner & click on youtube addon
Click on the download MP3 link
Close the pop-up ad and wait until finished
Folder with file will open when you click on it.
If you morons can't find out - go down and buy it!

easy to install and use. it just works. no better way to extract mp3 audio from videos.