The MOST universal video downloader add-on for Firefox there out there. Been using it for FREE for years, but just sprang for the $28 registration, so now it can even convert videos without the watermark. (Free version converts, but puts a QR code in the upper left corner.) I only wish I had given them my money sooner. Polished and feature-rich, you quickly get a feel for which (of the dozens) links to download. So, it's quick to learn, and POWERFUL for power users like me. 5 FULL stars! :)