promotional bannermobile promotional banner

Cleanroom relauncher unofficial

Launch Cleanroom on any launcher, or update your mmc instance to Cleanroom

THIS IS AN ALTERNATIVE, NOT A FORK!

This mod can:

  • Download and install Cleanroom automatically if you are running MMC-based launchers
  • Download and launch Cleanroom if you are using other launchers

Difference compare to official one:

  • A config option to use local Cleanroom mmc pack, which allow the installation of action builds
  • Allow modpacks to ship default config Cleanroom version and args
  • Proxy config for mmc zip & libraries downloading
  • Maven mirror. Only useful for players in certain regions though
  • Custom library path, allow reusing libraries with existing launchers

Highlight Features for Pack Makers

  • You can ship a custom default Cleanroom mmcpack with your pack, which won't be updated
  • You can ship a JRE with your pack (by filling relative path), so your players don't need to install new Java themselves
  • You can ship all libraries in your pack, which will means instant one-clicked relaunch

About Java 8u51

Official launcher ships with outdated Java 8u51 (released 2015), which doesn't contain certificates of later Let's Encrypt (used by Cleanroom maven) and Azure (used by libraries.minecraft.net).

The mod will add those certs into JVM if old java detected. In fact, I added whole keystore from latest Java.

But there's another bug in 8u51 that will cause deadlock in multi-thread downloading. Updating your JVM is always the best solution.

About bundled libraries & files

  • Apache Httpcomponents 5: Shadowed to use multi-thread download.
  • java-utils: Created by CleanroomMC, used to detect installed JVMs.
  • MigLayout: Used to provide a decent GUI layout.
  • sslcontext-kickstart: Used to import keystore.
  • cacerts.jks: Keystore copied from latest Temurin JRE 8.0.462+8.
  • mmcpack.zip: Latest Cleanroom 0.3.13-alpha mmc zip. Can be verified by comparing checksum to the release one.

 

If you want to…

  1. Update Cleanroom version: remove mmcpack.zip and mmcpack/ folder in relauncher/, then launch the game.
  2. Rollback to Forge: Disable the mod if you are using regular launcher, change game version, lwjgl version and Forge version back to regular in MMC instance setting if you are using that.

Note

By MMC-based launchers, I mean MultiMC, PolyMC and PrismLauncher.

You need to install a Java 21 to use this!

This is a client only mod! For server, please download installer jar from Cleanroom repository.

If anything gone wrong, remove cleanroom_relauncher.cfg config file and try again!

 

FAQ:

  • Q: What is Cleanroom?
  • A: Cleanroom is a 1.12.2 Forge fork, providing newer toolchain, new APIs and 99% compatibility. Our plan is to make 1.12.2 up-to-date with latest toolchain while adding more feature to Forge & vanilla, so we don't need to care about higher versions' X point release * Y Mod API headache.
  • Q: How to install Cleanroom?
  • A: Please follow the instructions in README.
  • Q: Can I include this in my Forge modpack? Will it crash my Forge pack?
  • A: Yes, you can, and it is safe! This mod won't be loaded or crash anything in a Forge environment.
  • Q: Java version?
  • A: 21 or 22. We are planning to support development using latest LTS version Java and running with latest Java.
  • Q: Current state?
  • A: Cleanroom have reached well usability, small packs like Tekkit 2 could be run out-of-box with Fugue, while larger pack like e2ee and Mystics Monstrosity is working after some tweaks. But we are lacking manpower, please join our Discord if you are willing to help.

The Cleanroom relauncher unofficial Team

profile avatar
  • 32
    Followers
  • 25
    Projects
  • 3.3M
    Downloads

More from kappa_maintainerView all

  • SauriaLib project image

    SauriaLib

    • 662
    • Mods

    A GeckoLib 3 fork with fixes and patches, for Cleanroom. Fully compatible with old mods.

    • 662
    • May 6, 2026
    • Mods
  • MoreMekaSuitModules project image

    MoreMekaSuitModules

    • 65.6K
    • Mods

    More Modules have been added to mekanism

    • 65.6K
    • April 1, 2026
    • Mods
  • Fugue project image

    Fugue

    • 704.6K
    • Mods

    A universal incompat patching mod for Cleanroom

    • 704.6K
    • April 1, 2026
    • Mods
  • 换行修复/WrapFix project image

    换行修复/WrapFix

    • 91.1K
    • Mods

    中英文混排换行修复/General line breaking fixing mod

    • 91.1K
    • March 26, 2026
    • Mods
    • +1
  • SauriaLib project image

    SauriaLib

    • 662
    • Mods

    A GeckoLib 3 fork with fixes and patches, for Cleanroom. Fully compatible with old mods.

    • 662
    • May 6, 2026
    • Mods
  • MoreMekaSuitModules project image

    MoreMekaSuitModules

    • 65.6K
    • Mods

    More Modules have been added to mekanism

    • 65.6K
    • April 1, 2026
    • Mods
  • Fugue project image

    Fugue

    • 704.6K
    • Mods

    A universal incompat patching mod for Cleanroom

    • 704.6K
    • April 1, 2026
    • Mods
  • 换行修复/WrapFix project image

    换行修复/WrapFix

    • 91.1K
    • Mods

    中英文混排换行修复/General line breaking fixing mod

    • 91.1K
    • March 26, 2026
    • Mods
    • +1