Very Happy to Write this Review. I am using this add on with Windows 7 with outdated Firefox and it does everything it says it does, The MP4 quality is the best you get on YouTube anyway. Ive had to teat dozens of these things and the others are rubbish or don't even pretend to p[ut the download button where it says. I cant say what privacy Ive had risked but at least it WORKS. Load the Y0uTube page, Press the small down arrow (its small nearly dismissed as more rubbish then saw it) press & choose Quality & it goes straight to nominated download location in firefox. You can clos the page any time & it still download even & you can start another any time> I am poor even I will Donate to this app.... on pension day) This app workd for me years ago too & currently with old XP & even older firefox.