UP TO FOUR PLAYERS. ONE ADVENTURE.

UNDERTALE CO-OP

Keep one launcher. Get new mod releases automatically when you open it.

DOWNLOAD WINDOWS APP (.EXE) ↓
  1. Save Play Undertale Co-op.exe somewhere easy to find, like your desktop. The app has the mod logo built in.
  2. Open Steam, close Undertale, then double-click the launcher.
  3. In the game, choose CO-OP → HOST or JOIN.

Send your friend this page. Everyone uses the same launcher and needs their own installed Windows Steam copy of Undertale v1.08.

NOW AVAILABLE · r58

The host can keep playing when a guest disconnects. Co-op uses the original 30 FPS for stability, and session reports preserve errors. Includes the idle party sidebar and health bars.

Updates install between game sessions. If an update check is offline, your last verified installation is still available. Keep this launcher for future published releases.