Minecraft Decompiled

Decompiled source from Mojang's unobfuscated JARs. No Loom, no Forge toolchains, just Vineflower and Gradle.

Starting with 1.21.11, Mojang ships unobfuscated JARs.

Requirements

• JDK 21+
• GraalVM 21+ (native builds)

Setup

./gradlew setup

Decompiles the client jar, splits into server/client sources, applies patches, done.

Build

./gradlew :server:compileJava
./gradlew :client:compileJava

Run

./gradlew runServer
./gradlew runClient

IntelliJ IDEA

Run runClient/runServer once before opening.

Hot reload requires JetBrains Runtime in Project Structure, IDEA must run under it too:

export IDEA_JDK="/usr/lib/jvm/java-21-jetbrains"

Structure

├── jars/              # vanilla jars
├── libs/              # decompiler linking libs
├── patches/           # decompiler fixes
├── mods/
│   ├── client/        # client patches (mymod.patch)
│   └── server/        # server patches (mymod.patch)
├── server/src/        # shared/server source
├── client/src/        # client-only source
├── native/            # GraalVM substitutions and configs
└── prism-instance/    # PrismLauncher instance template

Modding

Two-layer patch system:

1. patches/ - fixes for decompiler output (don't touch)
2. mods/client/ and mods/server/ - your named patches

Edit source, test, then generate a named patch:

./gradlew modGen -Pargs=client,mymod
./gradlew modGen -Pargs=server,mymod

This saves to mods/client/mymod.patch or mods/server/mymod.patch.

Applying Mods

Apply named patches to the source:

./gradlew modApply -Pargs=client,mod1,mod2,mod3
./gradlew modApply -Pargs=server,mod1,mod2,mod3

Patches are applied in order. If a patch fails:

• Already applied? Use modRevert first
• Conflicting mod? Revert the other mod first

Reverting Mods

Reverse patches (in reverse order):

./gradlew modRevert -Pargs=client,mod1,mod2,mod3
./gradlew modRevert -Pargs=server,mod1,mod2,mod3

If revert fails, the patch was likely already reverted or never applied.

Packing Mods

Pack changed classes into a zip for distribution:

./gradlew modPackClient
./gradlew modPackServer

Compiles current source and outputs changed classes to mods/client.zip or mods/server.zip.

Using with PrismLauncher

Old-school jar modding is back. To use your mods with PrismLauncher:

1. Copy the instance template:

   cp -r prism-instance ~/.local/share/PrismLauncher/instances/my-modded-mc

2. Add your mod classes:

   cp mods/client.zip ~/.local/share/PrismLauncher/instances/my-modded-mc/jarmods/

3. Restart PrismLauncher:

   1. There should be a new instance My Modded Minecraft
   2. You can edit it to toggle Unobfuscated component to disable unobfuscated client
   3. Or you can toggle Mods component to disable your mods

The jarMods system merges your classes on top of the base jar at runtime.

Instance Structure

prism-instance/
├── instance.cfg                    # instance name/type
├── mmc-pack.json                   # components list
├── jarmods/
│   └── client.zip                  # your compiled mod classes
└── patches/
    ├── custom.unobfuscated.json    # unobfuscated jar override
    └── custom.mods.json            # jarMods component

Native Builds

Requires ./gradlew setup first.

Build

./gradlew nativeServer
./gradlew nativeClient

Run

./gradlew runNativeServer
./gradlew runNativeClient

Reachability Metadata

Run the game, trigger as many code paths as possible, then quit. Agent merges into native/configs/, can be run multiple times.

./gradlew nativeServerAgent
./gradlew nativeClientAgent

Decompiler

Uses Vineflower with standard flags. Patches fix type inference issues, lambda captures, and other decompiler artifacts.

Legal

Mojang owns this code. See LICENSE.