Tbh, this add-on isn't very useful anymore purely for the fact that website version of youtube now does everything this add-on does. I'm giving it four stars because it is extremely useful and convenient had youtube not updated to do similar/the same things. The only thing that this add-on does that youtube does not is that this changes a videos ratio/size to be smaller so it appears clearer/higher resolution. A lot of negative reviews complain that it causes videos to be stuck as a small box in the corner of the screen or that it makes the video unable to go full screen. What they probably did and ont realize is that they set the resolution for the add-on to 2440p(4k) and tried to watch a video that's highest resolution is only 480p-720p. The add-on can't upscale the video's quality and magically add 8,294,400 pixels of detail and information it neither had nor was even programmed to find and jigsaw together onto however many frames-per-second in real-time in the first place either... especially not for free.