2025 (6 years after my previous review)
I've given the add-on 5* stars because it's been great since I started using it about a decade ago. The developers do their best to make corrections to the code when YouTube & other websites make changes to there download codes. As a token of my appreciation I will be making another donation in the next couple months. A big "Thank You" to the developers for creating this wonderful Add-on and for keeping it updated.

My previous review (given, 6 years ago)
I would have given it 4.5 *stars instead of 4 stars if I could have. I am using Windows XP Pro w/ FF ver 52.7.3 and have been able to download about 90-95% of YouTube vids and maybe 80-85% of vids from other websites. Some download problems I would think come about because of my dated O/S & FF version. All-in-all I do a lot of research & this has been my main download app the past few years. I made a donation a few years ago ($25 or $35) and I am going to make another after I finish writing this review ... A big thanks to the developers!