OpenComputers for Minecraft 1.21.1

This repository is a community-maintained NeoForge port of the original OpenComputers. It keeps the classic Lua computers, robots, drones, component network, and OpenOS experience on modern Minecraft.

Warning

The 1.21.1 port is under active development. Back up worlds before testing it, and expect incomplete integrations and compatibility work.

Requirements

• Minecraft 1.21.1
• NeoForge 21.1 or newer
• Java 21
• ScalableCatsForce for NeoForge 3.3.3

Installation

Download a release or CI build and put both of these files in the instance's mods directory:

• opencomputers-*.jar
• scalablecatsforce-neoforge-*-with-library.jar

The ScalableCatsForce JAR is included beside OpenComputers in local build outputs and CI artifacts.

Building

Clone the repository and run:

.\gradlew.bat build

On Linux or macOS, use ./gradlew build. Java 21 is required. Build artifacts are written to build/libs.

For an IntelliJ IDEA development environment, enable the Scala plugin and import the repository as a Gradle project. Launch the game with the Minecraft Client Gradle run configuration or the runClient Gradle task. Do not run net.neoforged.devlaunch.Main directly; that bypasses ModDev's launch preparation.

If IntelliJ reports that build/moddev/clientRunVmArgs.txt is missing, run:

.\gradlew.bat prepareClientRun

Then launch Minecraft Client or runClient again. The normal runClient task already depends on prepareClientRun, including after clean.

Project status

The port currently targets NeoForge 1.21.1. Remaining integrations and planned features are tracked in ROADMAP.md. The original OpenComputers wiki is still useful for gameplay and Lua API concepts, but some installation and mod-integration details describe older Minecraft versions.

Useful project links:

• Issues
• Actions and development builds
• Releases
• In-game manual sources
• Lua/OpenOS sources
• Java API sources

Contributing

Bug fixes, focused ports, documentation improvements, translations, and small Lua programs are welcome. Please keep changes scoped, preserve compatibility where practical, and run gradlew build before opening a pull request.

Translations live in src/main/resources/assets/opencomputers/lang. The English locale is the source of truth for keys. Instructions for adding loot-disk programs are in the loot README.

Using the API

API artifacts use the Maven coordinates li.cil.oc:opencomputers with the api classifier. Published versions are available from:

repositories {
    maven { url = "https://maven.michiyo.me/releases/" }
}

dependencies {
    compileOnly "li.cil.oc:opencomputers:<version>:api"
}

Match <version> to the release or build you target.

License

OpenComputers code is available under the MIT License. Most original assets and localization strings are dedicated to the public domain under CC0; exceptions are identified in the main license. Bundled and adapted third-party work is documented in THIRD_PARTY_NOTICES.md, with the corresponding license texts in LICENSES.

OpenComputers may be included in modpacks, subject to those license terms and attribution notices.

Thanks to Florian "Sangar" Nücke, Vexatos, payonel, magik6k, Lord Joda, the OpenComputers contributors, and the maintainers of the modern ports.