It is broken. Youtube has changed something to the effect that the video file extensions and the audio file extensions are switched.
The workaround (manually renaming the files as they are saved to disk) is kind of a pain in the ass.

Also, switching the "Homepage" from:
https://github.com/inbasic/iaextractor/
to:
https://addons.mozilla.org/en-US/firefox/addon/youtube_downloader_webx/
would be very nice.

Very good addon/works well. I would like to see it have an option to remember the last folder saved to, as I save to many different folders and it gets tedious to have to drill down to a specific folder when downloading similar videos each time.

Does NOT download both the audio and the video and combine them for you. 3-19-18 Firefox 59.0.1

Good

Works really well with Youtube. :)

virus un .bat comme d'hab ( j'ai même pas télécharger l'extension ptdr(plié tordu de rire) tas de merde !

pas de conversion mp3, le fichier en supplément dans le module firefox demande de télécharger un logiciel a pars de firefox (2 modules et un executable en plus, de la merde...

It properly enlists what is on the Youtube website. The best part is to download the Audio-only file which was one of the features of Flashgot, but not working in Quantum.
Thank you

That is the best

I try new version and I didn´t find how to configure for downloading only audio.
Now I am using little bit more uncomfortable
https://addons.mozilla.org/en-US/firefox/addon/simple-youtube-converter

but it works :-/

I would rate this four stars if it did not mangle the filenames. It replaces characters like a comma or parentheses with a hyphen (it's becomes it-s).

使いやすい、わかりやすい、動作も機敏、すばらしい。

Easy use, easy understand and Quickly, so good.

It works well on all videos I've tried and with ease! Also, I love the media converter and muxer.

Good on. I have used the old one for years. This one needs (more correctly, I want) two tweaks. Firstly, let us specify the directory to save the original video file in. We have the option for the converted audio file but not the original video. It always goes in Downloads. Secondly, let us specify the path to ffmpeg rather than install another copy. Most of our systems have ffmpeg already, just verify the path. Thanks for the good product. My grandchildren love mp3s that I get from the Youtube videos.

ottimo programma