Hide videos seen on Youtube, on any page, by X'ing them
YouTube Hide Watched is a userscript allowing you to keep track of which videos you've watched by hovering over the thumbnail and X'ing them. This has been tested to work on pretty much every page. It stays after refreshing (do not clear YouTube's cookies, specifically LocalStorage, to maintain which ones stay hidden). There is a "Show hidden" button at the bottom of the page to temporarily reshow the ones that are hidden.
