Works! I have a mac and use firefox, and at the time of writing this, the extension does what says it'll do. The icon appeared, I asked it to download a video off youtube, it did, job done.

Extremely complicated installation. I followed the first step in the "About this extension" section, install "native client" (whatever that is) - nothing. I don't really need or want HD - my connection has a data limit - but I decided to try installing the ffmpeg thing too. It hasn't helped. The icon below the video produces a big orange box with only an hourglass in it. "Quick download" (upper right corner of the browser screen) produces a "Please Wait" message but the browser shows no download in progress and if there is one, I have no idea where it's been saved (I looked in all the usual places). The Settings page includes something about an "ffmpeg path" with a box that's empty; maybe it's supposed to have something in it but I don't know what. I don't understand most of what's on that Settings page anyway. This extension may be fine for people with a lot of knowledge of how addons work but that doesn't include me and I'm stumped. From my point of view, basically - it doesn't download anything and I don't know what to do to make it start. I'm removing it.

By default, is not working for audio-only, downloaded files not working ... need more steps !

Update August 2024: unfortunately the addon no longer works because YouTube has announced a war on ad blockers.

Old review: Version 1.1.8 sadly doesn't work - shows an hourglass indefinitely. Waiting for a fix.

Would be great if you added support for music.youtube.com

All I can say is WOW!!! An HD YouTube downloader that actually downloads the video as HD!!!

update 1.1.3 coming at 12/9 and its working fine again!

Now: Unable to retrive data....Doesn t work :(

Did not work. Video metadata error. Searched for Kaner extension, which worked.

It is useless, you have three options:
1)download 320p video AND audio;
2)download video BUT NO SOUND
3)download audio but with ads AND JUST SOMETIMES!

Stupid.

Ya no sirve

This add-on is quite good, despite the recent issue I've had with it. That recent issue being that I was unable to download videos until using a VPN to hop to a different IP address. Then, the add-on worked just like it used to in the past. No idea what's going on right now, but hopefully developer gets this issue sorted out in the near future.