I have used this Add-On to download over 100 videos from many different sites. There are a fair amount of videos that this will not download but you won't find a better alternative. I have compared this to several other video downloader add-ons and this is the best.
TLDR; INSTALL THIS ADD-ON AND GIVE THEM A TIP AFTER YOU'RE SATISFIED WITH ITS USE

excelente aplicacion la recomiendo ampliamente

Works fine to extract videos. Thanks for the complex add-on!

goog

Excelente!!

Super

輕鬆 簡單 便利

Excelente!!!!

Excelente!

Muy buena aplicación. Para mi la mejor.

Gebruiker sinds jaren, tot volle tevredenheid. Eenvoudig in gebruik, werkt vrijwel altijd.

Sehr praktisch!

Does exactly what it says it does . I have yet to have a problem with this exceptional add on!

In my opinion, this is the best downloader for firefox I have used. It gets a bit shaky on YouTube, but otherwise I have not had any real problems with it.