Osu! is a rhythm action game where you tap the screen in time to the music similar to the Elite Beat Agents games. This starts as a simple challenge but develops in speed and complexity. At higher levels, the games is an esport with people competing to get the highest scores.

Osu was originally released for PC and has since come to Android and iOS (Osu Stream). Its gameplay is inspired by other rhythm games, although without the story elements that were often included in these games: Osu! Tatakae! Ouendan, Taiko no Tatsujin, Happy Feet, Elite Beat Agents, StepMania, and DJMax. The game has a strong community of players and creators making custom levels through the community-made in-game editor.

Play involves tracking an on-screen target with a mouse or trackpad and then accurately pressing a couple of keys in time with the prompts and music. These prompts can be a line to trace, points to hit, spinners to spin and other more complex patterns.