Client

How to Install Cleanroom Loader on the Client

About Launchers

The recommended way to run Cleanroom Loader is with a MultiMC-based launcher, such as Prism Launcher or PolyMC.

These are officially supported because other launchers may not properly handle the removal of certain vanilla libraries.

Manual Install

Note

Importing Cleanroom Loader instance is only supported on MultiMC-based launchers. For other launchers, use the installer jar.

Steps:

1. Add Fugue to your mod folder
   (it will not load in a Forge environment)
   
2. Add Scalar Legacy to your mod folder
   (it will not load in a Forge environment)
   
3. ⚠️ Warning: Make sure your instance does not include problematic or deprecated mods.
   See Preparing your modpack for more details.
   
4. Download the Cleanroom-MMC-instance- archive from the Releases page.
   
5. Import it into your launcher.
   (Alternatively, unzip the patches and JSON files into an existing 1.12 instance.)
   
6. In your launcher, select the javaw.exe path of your Java 25 installation. (javaw.exe will not produce any command-line output and it the one that should be used in normal cases, while java.exe will produce a command-line output)
   
7. (Optional) Add JVM arguments as described in the JVM Arguments section.
   

Cleanroom Relauncher

Cleanroom Relauncher is a Client-side mod that allows you to start a Forge 1.12.2 instance and seamlessly switch to Cleanroom Loader.

This is particularly useful for modpack authors who want to distribute Forge-compatible packs that can also run on Cleanroom.
It is supported in both MultiMC-based launchers and standard launchers.
Steps:

1. Add Fugue to your modlist
   
   (it will not load in a Forge environment)
   
2. Add Scalar Legacy to your modlist
   
   (it will not load in a Forge environment)
   
3. ⚠️ Warning: Ensure your instance does not contain problematic or deprecated mods.
   
   See Preparing your modpack for details.
   
4. Add the Cleanroom Relauncher mod to your modlist and launch the game with Java 8.
   
5. In the Cleanroom Relauncher GUI, select the javaw.exe path of your Java 25 installation. (javaw.exe will not produce any command-line output and it the one that should be used in normal cases, while java.exe will produce a command-line output)
   
6. (Optional) Add JVM arguments from the JVM Arguments section.
   
7. Click Relaunch.
   

Notes

• Cleanroom Relauncher’s configuration file can be found at config/relauncher.cfg.
  Deleting this file will prompt the setup GUI on the next launch.
  

  Note

  Cleanroom Relauncher will check for cleanroom updates. Therefore, the UI will launch when an update rolls out.

• ⚠️ Warning: Not all launchers are compatible with Cleanroom Loader.
  Supported launchers:
  • ✅ MultiMC-based launchers (Prism Launcher, PolyMC, etc.)
    
  • ⚠️ CurseForge Launcher (limited support)
    
  • ⚠️ Official Minecraft Launcher (limited support)
    

Contributors

Thermonuclear_Minecraft_Engineer

Last edited 11 days ago

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