Prism-MC-Updater

Description

A powerful yet simple Minecraft version auto-updater for PrismLauncher and MultiMC instances.

It ensures your selected instance always launches the latest release or snapshot version of Minecraft — without needing to manually adjust the configuration every time Mojang pushes an update.

Features

• Supports both release and snapshot Minecraft versions
• Fully compatible with PrismLauncher wrapper commands
• Can still be used as a pre-launch command (works in MultiMC, but may not be effective in newer PrismLauncher versions due to config overwrite behavior)
• Detects whether an update is needed before patching
• Can auto-relaunch the launcher with updated version settings if needed

Installation

1. Download the latest script from:

   • Codeberg Releases
   • GitHub Releases

2. Make the script executable (Linux/macOS):

   chmod +x mc-update.py

Requirements

• Python 3.x installed
• MultiMC or PrismLauncher installed

Usage

A) PrismLauncher Wrapper Mode (Recommended for Prism)

1. Open PrismLauncher.
2. Right-click your instance → Folder
3. Place the script inside the opened instance directory
4. Right-click your instance → Edit → Settings tab.
5. Under Custom Commands, paste the following into the Wrapper Command field:

Basic usage (default: latest release)

• Linux/macOS:

  python3 "$INST_DIR/mc-update.py"

• Windows:

  python "%INST_DIR%\\mc-update.py"

Most of these commands are defined for Linux/macOS
If you are on Windows you will need to change them to fit the format above.

With snapshot version:

python3 "$INST_DIR/mc-update.py" --snapshot

With custom Prism path and subprocess logging:

python3 "$INST_DIR/mc-update.py" --snapshot --prism_path "/usr/bin/prismlauncher" --subprocess_log

With optirun or other GPU wrappers:

python3 "$INST_DIR/mc-update.py" --end_up_wrapper optirun

All wrapper arguments go before --end_up_wrapper. Anything after that is treated as the command to run Minecraft (usually inserted automatically by PrismLauncher).

B) MultiMC Pre-Launch Command (Still works)

For legacy behavior (or when using MultiMC instead of PrismLauncher):

1. Open MultiMC.
2. Right-click your instance → Folder
3. Place the script inside the opened instance directory
4. Go to your instance's Settings → Custom Commands tab.
5. Add the following as the pre-launch command:

Release version (default):

• Linux/macOS:

  python3 "$INST_DIR/mc-update.py"

• Windows:

  python "%INST_DIR%\\mc-update.py"

Snapshot version:

python3 "$INST_DIR/mc-update.py" --snapshot

Options

Behavior

• If the instance already has the latest version: it starts normally.
• If an update is needed:
  • The wrapper exits, and a delayed subprocess patches the config and relaunches the instance using PrismLauncher.
• If run as a pre-launch command in MultiMC: the config is patched before the launcher starts the game.

FAQ

What happens if I updated the game manually?

Well it will say it's up to date and close itself.
Afterwards the game should start as usual.

Can I compile the script with PyInstaller?

I did not test it.
You can try it, it may work but no promises.

What is the difference between wrapper and pre-command?

Both the wrapper and pre-command options allow you to run custom scripts before launching Minecraft,
but they serve slightly different purposes and are handled differently by PrismLauncher and MultiMC.

Pre-Command (Simple)

• Runs before anything else.
• Executes your script before the launcher touches any game files or starts Minecraft.
• Ideal for simple one-shot tasks like updating files or running quick checks.
• Works well in MultiMC.
• In PrismLauncher, this may not work as expected, because it applies config changes after the pre-command runs, potentially overwriting them.

Wrapper (Advanced – Recommended for PrismLauncher)

• Replaces the actual Minecraft launch command.
• PrismLauncher starts your script instead of the game.
• This script receives the full game command as arguments, allowing it to:
  • Check if an update is needed
  • Close cleanly if not (game would run after that)
  • Or relaunch PrismLauncher after patching the version
• More flexible and reliable for complex tasks
• Required if you want proper version patching in PrismLauncher, since config changes need to happen after Prism’s own logic completes.