OSZ files are used by the game OSU! in which players click and follow various circles and trails rhythmically timed to the song. The OSZ files are a compressed form of the OSU beatmap file which contains the beat timing, graphics/videos, the song, and the locations of the trails and circles that are to be clicked. These files also allow the beatmaps to be shared with other players.

These files can be added to the game either by dragging the files in to the game, double-clicking the file, or by adding it through the in-game menus.