.OSU File Extension
File TypeOsu! Script
What is an OSU file?
Game script written for osu!, a rhythm game where players click hit circles in sync with music; saves properties for a game challenge, such as the difficulty, the song that is played, and the timing points for hit objects; can be used by game community members for making custom challenges.
OSU files are ultimately built with the other game level files into .OSZ files, which can be imported and run in osu!.