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 · r59

Take individual turns: the active Steam name turns yellow, their action finishes, and the next player takes over before the monster acts. Includes disconnect recovery, native co-op timing, and session reports.

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.