Direct YouTube downloads MP3 M4A AAC and HD MP4, FLV, 3GP. With just one mouse click! With the click off an mouse button! Super fast downloads right from the YouTube video page you are viewing.
Here are more details from the developer:
Download every YouTube video you want and you can download them as HD MP4, FLV, 3GP, MP3, M4A and AAC formats. With the click off an mouse button! Direct single click downloads at fast speeds!.
Super fast downloads right from the Youtube video page you are viewing without requiring any additional software or visiting any third-party website riddled with advertisements.
Want to learn more? You can grab it on the Firefox Add-ons website.