Most games on UBG64 are copyrighted. Unless the game developer explicitly releases their title as open-source or freeware (like many .IO games), hosting the game without permission is copyright infringement. Large studios like Nintendo or Sega frequently issue DMCA takedown notices against unblocked sites. This is why you may visit UBG64 one day to play Super Mario and find it gone the next.
Here are 5 safe, fun, browser-based games that rarely get blocked: Most games on UBG64 are copyrighted