Being a Firefox user since 2004, I think this is the best YouTube downloader add on that I've ever used. It works like a charm. I installed it then I forgot, due to its unobtrusive UX. But when I need to download something on YouTube, the button is there sitting right below the video. No ads, no complex settings--it just works the way I imagine it to work. Don't take my word for it. Almost 6,000 users rated this add on 5-star; very little gave 2- to 4-star. As for the rest 1,400 users who rated 1-star, I think they are just confused because this add on suddenly stopped working. You can read their comments. It is very understandable that YouTube doesn't like this kind of add on and they will try to change their codes every now and then. Sometimes a YouTube downloader add on will break because of it, and we just need to be patient until the developer releases the fix for it. Any other downloader add on faces the same problem. I think this add on is one of the fastest (if not the fastest) add ons to release the fix. I really recommend this add on.