UndertaleModTool

krzys-h · Developer Tools

The most complete tool for modding, decompiling and unpacking Undertale (and other Game Maker: Studio games!)

Publisher

krzys-h

Version

0.9.0.0 Latest

License

GPL-3.0

Description

The most complete tool for modding, decompiling and unpacking Undertale (and other GameMaker games!) Main Features: - Can read every single byte from the data file for latest versions of Undertale, Deltarune, and most other GameMaker games, and then recreate a byte-for-byte exact copy from the decoded data. - Properly handles all of the pointers in the file so that if you add/remove stuff, make things longer/shorter, move them around, etc., the file format won't break. - An editor which lets you change (almost) every single value, including unknown ones. - Includes a simple room/level editor. - Allows for GML VM code editing. This means you can add any custom code to a game, either using the built-in GML compiler or GML assembly. (YYC is not supported for this.) - High-level GML decompiler and compiler. Supports a large range of GameMaker versions, and most important GML features (still missing a few). - Support for running scripts that automatically modify your data file (or perform other nefarious tasks). This can be used for mod distribution, aside from other methods such as file patches/project systems. - All core functionality extracted into a library for use in external tools. - Can generate a .yydebug file for the GM:S debugger so that you can edit variables live! (see here) - Automatic file associations for all GameMaker related data files. This is opt-in at the first boot of the tool, and can also be disabled by having a dna.txt file next to the executable.

UndertaleModTool is available through winget as package ID krzys-h.UndertaleModTool, with version 0.9.0.0. Use the install command above to set it up on Windows without downloading a separate installer manually.