Contributing Guide

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Build HMCL

Requirements

To build the HMCL launcher, you need to install JDK 17 (or higher). You can download it here: Download Liberica JDK.

After installing the JDK, make sure the JAVA_HOME environment variable points to the required JDK directory. You can check the JDK version that JAVA_HOME points to like this:

PowerShell:

PS > & "$env:JAVA_HOME/bin/java.exe" -version
openjdk version "25" 2025-09-16 LTS
OpenJDK Runtime Environment (build 25+37-LTS)
OpenJDK 64-Bit Server VM (build 25+37-LTS, mixed mode, sharing)

> $JAVA_HOME/bin/java -version
openjdk version "25" 2025-09-16 LTS
OpenJDK Runtime Environment (build 25+37-LTS)
OpenJDK 64-Bit Server VM (build 25+37-LTS, mixed mode, sharing)

> /usr/libexec/java_home --exec java -version
openjdk version "25" 2025-09-16 LTS
OpenJDK Runtime Environment (build 25+37-LTS)
OpenJDK 64-Bit Server VM (build 25+37-LTS, mixed mode, sharing)

Get HMCL Source Code

• You can get the latest source code via Git:
  shellCopy

  git clone https://github.com/HMCL-dev/HMCL.git
  cd HMCL
  

• You can manually download a specific version of the source code from the GitHub Release page.

Build HMCL

To build HMCL, switch to the root directory of the HMCL project and run the following command:

./gradlew clean makeExecutables

The built HMCL program files are located in the HMCL/build/libs subdirectory under the project root.

Debug Options

[!WARNING] This document describes HMCL's internal features, which we do not guarantee to be stable and may be modified or removed at any time.

Please use these features with caution, as improper use may cause HMCL to behave abnormally or even crash.

HMCL provides a series of debug options to control the behavior of the launcher.

These options can be specified via environment variables or JVM parameters. If both are present, JVM parameters will override the environment variable settings.