It's free, it's not nagware, it can download audio or full HD video, and it works (at the moment), so what more can you ask for?
Note that to download video with audio, click on a "video-only" option with ffmpeg installed, and the video will be merged with the audio when finished. Installing ffmpeg correctly was a bit finicky though. And audio files downloaded without ffmpeg wont play on my phone. Download speed for audio is kinda slow, but it's much faster for HD video.
Great to see it working again!

This add-on downloads with less than a twelfth of 2CONV's, Mpgun's and others download speed, so I'd rather use the online downloaders.

This download speed is really slow no more than 100KB

Worked once, never worked again.

1.2.1
It works fine. Thank you for the wonderful work.

As of 1.2.1 problems seem to be fixed and it works OK.

Very good function of this addon. And especially now where the adjustments to new versions of Firefox happen quite quick.

Just the speeds of the Downloads are extremely low, like 1MBit/s. Is that due to the Native Client or can I fix something?

Funciona perfecto con Firefox 96.0.3 (YD 1.1.7.2)
El mejor downloader de este planeta. Y probablemente el mejor de este Sistema Solar :-)

Hey folks, I just updated firefox to v96.0.3 and now YouTube Video and Audio Downloader is working again. I have version 1.1.8 Hurray!!! I have "Allow Automatic Updates" set to "On," so it might have automatically downgraded to an earlier version, but it still says 1.1.8 in my extension panel.

used to work great. latest version does not work at all.

This quit working about a month ago. I cant use it any more.

It used to be an excellent add-on for downloading audio, but it doesn't work anymore.
Приложение перестало работать !!!

It used to be an excellent add-on for downloading audio, but it doesn't work anymore.

TO FIX THE PROBLEM, I went back to version 1.1.6 which also uses the older detection algorithm and that works great for me (five stars great). Other users may want to do the same until the bugs are worked out of the latest release. On the options page for this extension, I set "Allow automatic updates" to OFF since I don't want 1.1.6 to be replaced by that buggy new version. Once the bugs are fixed, I'll set it back to the Default value again.

The older 1.1.6 version was obtained by going to the bottom left side of the Firefox Add-On page for this extension. You see a clickable link to See All Versions.

If you only get the spinning hourglass, check if you're running version 1.1.7, if so, just downgrade to 1.1.6 again