Does a great job of changing the background to black, however, it has a couple bugs. The biggest issue, is that the video description gets completely removed while this extension is active. If you try to click where it should be, it expands the description area, but it is still entirely black. There is also a bug where the video controls have a solid black background, which is a mild annoyance. If the video description did not disappear, this would easily be a 4-5 star extension.