The osu! replay is not a video file but a binary file with the extension .osr . Its compact size (typically 10–200 KB) enables efficient storage and sharing. The format consists of the following data blocks:
is a free-to-play rhythm game renowned for its precision-based gameplay and competitive community. A core component of the game’s ecosystem is the Replay Viewer – a built-in tool that records, stores, and plays back every user’s performance. Unlike simple video recordings, the osu! replay system is data-driven , capturing raw input sequences. This paper provides a technical and functional overview of the Replay Viewer, examining how it works, what data it contains, and how players, coaches, and developers use it. osu replay viewer