# UnderminersTeam/UndertaleModTool

The most complete tool for modding, decompiling and unpacking Undertale (and other GameMaker games!)

Repository: https://github.com/UnderminersTeam/UndertaleModTool
Canonical: https://ross.abutalabs.com/products/undertalemodtool
Homepage: https://underminersteam.github.io/
Language: C#
License: GPL-3.0
License Family: copyleft
Topics: game-maker-studio, decompiler, undertale, unpacker, editor, deltarune, gml, gamemaker, game-maker, game-maker-studio-2
Last push: 2026-08-24T02:24:29+00:00

## Health v2 (maintenance only)
Score: 95/100 (v2, computed 2026-09-03T02:39:23.370411+00:00)
- activity 99, release rhythm 87, longevity 100
- inputs: {"age_days": 2911, "days_push": 10, "days_rel": 10, "gap_med": 30.5, "n_releases_24m": 13}
- flags: none
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 2012, forks 355 (observed 2026-08-28T04:06:05.095189+00:00)

## What it is
A GUI and CLI tool for modding, decompiling, and unpacking Undertale, Deltarune, and other GameMaker Studio games. It provides editors for GameMaker assets and code, GML decompilation/compilation, and scriptable extensibility via C#.

## Use cases
- mod undertale
- decompile gamemaker game code
- unpack data.win file
- edit deltarune sprites and rooms
- decompile gml bytecode
- extract assets from game maker studio game
- script batch edits on gamemaker data files

## When to choose
- modding or inspecting Undertale, Deltarune, or any GameMaker Studio 1/2 game
- you need accurate byte-level round-tripping of data.win files
- you want GML decompilation plus asset editors in one tool
- you need automation via CLI or C# scripts

## When to avoid
- you need a native Linux/macOS GUI - only CLI or Wine work there
- the game is not built with GameMaker
- you want a general-purpose game engine editor rather than a data file modding tool

## Facets
- artifact type: application
- maturity: active
- function: editor, parser, reverse-engineering, cli, gui
- domain: developer-tools, reverse-engineering, gaming-tools
- platform: windows, cli, cross-platform
- tags: gamemaker, undertale, deltarune, gml, decompiler, unpacker, modding, data-win, game-development

## Member repositories
- UnderminersTeam/UndertaleModTool (main) score 95

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:06:05.095189+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T03:01:01.675925+00:00, confidence not recorded.
  - readme: https://github.com/UnderminersTeam/UndertaleModTool (fetched 2026-08-28T04:06:05.095189+00:00, sha 669cab43e073)
  - homepage: https://underminersteam.github.io/ (fetched 2026-08-29T10:40:52.976087+00:00, sha 5cea6489c702)
- Data as of 2026-08-30T08:39:29.467469+00:00.