A Nintendo Switch port of Undertale Yellow 1.3.1
Undertale Yellow NX is a Nintendo Switch port based on a decompilation of Undertale Yellow 1.3.1. The project uses GameMaker runtime 2023.8.2.152 and is presented as version 1.0.
Saves work provisionally, with limited testing
The release notes say the build was not tested thoroughly, but saves appeared to be working during the project’s testing. That makes save behavior a positive early result, while leaving room for additional verification as the port receives more testing.
The version-tagged README lists persistent saves as a future task. This appears alongside the release’s report that saves are working, so it should not be read as confirmation of a fully verified or finalized save system.
Eight-direction joystick input is the main known issue
The joystick currently appears to register eight directions instead of full analog motion. The release notes identify this as an issue that also exists in the PC game, rather than presenting it as a new Switch-only problem. Players should therefore expect less granular stick movement.
Version and package details
The v1.0 release was published on August 30, 2026, and includes an NSP package named Undertale.Yellow.nsp. Its listed size is 361,572,568 bytes. Beyond the save status and joystick behavior, the release notes do not provide a broader compatibility report, performance measurements or a detailed list of changes.
