YYToolkit

YYToolkit is a tool for creating mods and altering GameMaker games, supported on Windows 8.1 → Windows 11.

Features

• Plugin Support
  • Run custom code in the game's context via a robust callback system
  • Detour game functions to your plugin to implement custom functionality
• Well-documented
  • The wiki has most API functions documented for both YYTK Legacy and YYTK Next
• Full access to GameMaker functions, scripts, and variables
• Full compatibility with existing tools like UndertaleModTool or Dogscepter
• Runtime loading / unloading
  • Mods can be managed seamlessly while the game is running

Getting help

• Help with YYToolkit or Aurie Framework - Arch Wizards Server
• General game modding questions - Underminers Server

YYTK Editions

YYTK is split on two branches, that being Legacy and Stable (Next).

Note

❌ = Unsupported 🟠 = Limited support 🟡 = Supported, unreliable ✅ = Supported

Point of comparison	YYToolkit Legacy	YYToolkit Next
GM 1.4.x	🟡	❌
GM 2.x.x	✅	🟠
GM 2022.x	🟠	✅
GM 2023.x	❌	✅
GM 2024.x beta	❌	✅
VM runner support	✅	🟡
x86 runner support	✅	🟡
x64 runner support	🟡	✅
Active Development	❌	✅
Accessing global variables	✅	✅
Accessing local variables	🟠	✅
Accessing built-in variables	❌	✅
Accessing data structures	❌	✅
Accessing scripts	🟡	✅
Accessing rooms	❌	✅
Manipulating object events	❌	🟠

Contributors

• YYTK Next
  • mashirochan for the awesome work on streamlining the installation process
  • PippleCultist for reporting bugs
  • ramennnoodle for creating how-to guides on getting YYToolkit and Aurie running on Linux
• YYTK Legacy
  • MousieDev for creating makefiles (which probably don't work at this point)
  • Miepee for the awesome icon!
  • TheEternalShine for testing and giving feedback on in-development versions of the tool.