This project aims to be the backbone for vintage minecraft modpacks, or simply a solid ground for players who want to enjoy their old favorite mods.

It is based off of CleanroomMC, which is a rewrite/fork of Forge, that aims to bring modern improvements to the older 1.12.2 Minecraft, like the usage of newer Java versions (Java 21), while keeping mod compatibility as high as possible.

The installation isn't straightfoward as you'll require a second step after having installed the modpack via your launcher of choice:

For MultiMC/Prism :

Download CleanroomMC MMC instance : https://github.com/CleanroomMC/Cleanroom/releases/download/0.3.0-alpha/Cleanroom-MMC-instance-0.3.0-alpha.zip
Locate your instance folder, where the libraries, minecraft and patches folder, among other files are located. This folder is easily found by right clicking your instance on the launcher and selecting Folder
Extract the content of Cleanroom-MMC-instance-0.3.0-alpha.zip in that folder.
Override existing data : If you aren't prompted to, you're doing something wrong.

For Curseforge :

Optionally you can use these java arguments :

-XX:+UnlockExperimentalVMOptions -XX:+UseZGC -XX:+ZGenerational -XX:+DisableExplicitGC -XX:+AlwaysPreTouch -XX:+PerfDisableSharedMem -XX:+ParallelRefProcEnabled -XX:+UnlockDiagnosticVMOptions -XX:+UseStringDeduplication -XX:+OptimizeStringConcat -XX:+UseCriticalJavaThreadPriority -XX:+UseNUMA

Under "Settings / Java / JVM arguments:" for MultiMC/Prism
Under for Curseforge

For more info about CleanroomMC, please visit : https://github.com/CleanroomMC/

Granite