v4 • minecraft‑java‑core

minecraft‑java‑core is a NodeJS/TypeScript solution for launching both vanilla and modded Minecraft Java Edition without juggling JSON manifests, assets, libraries or Java runtimes yourself. Think of it as the core of an Electron/NW.js/CLI launcher.

Getting support

Need help or just want to chat? Join the community Discord!

Installing

npm i minecraft-java-core
# or
yarn add minecraft-java-core

Requirements: Node ≥ 18, TypeScript (only if you import .ts), 7‑Zip embedded binary.

Standard Example (ESM)

import { Launch, Microsoft } from 'minecraft-java-core';

// ⚠️  In production, perform auth **before** initialising the launcher
//     so you can handle refresh / error flows cleanly.
const auth = await Microsoft.auth({
  client_id: '00000000-0000-0000-0000-000000000000',
  type: 'terminal' // 'electron' | 'nwjs'
});

const launcher = new Launch();

launcher.on('progress', p => console.log(`[DL] ${p}%`))
        .on('data', line => process.stdout.write(line))
        .on('close', () => console.log('Game exited.'));

await launcher.launch({
  root: './minecraft',
  authenticator: auth,
  version: '1.20.4',
  loader: { type: 'fabric', build: '0.15.9' },
  memory: { min: '2G', max: '4G' }
});

Documentation

Launch class

| Function | Type | Description | |----------|---------|------------------------------------------------------------------------| | launch | Promise | Launches Minecraft with the given LaunchOptions (see below). |

LaunchOptions

| Parameter | Type | Description | Required | |-----------|------|-------------|----------| | path | String | Working directory where game files are stored (usually .minecraft). | ✔︎ | | url | String | null | Custom version manifest base URL (only for mirror setups). | — | | authenticator | Object | Microsoft / Mojang / AZauth profile returned by the authenticator. | ✔︎ | | timeout | Integer | Network timeout in milliseconds for downloads. | — | | version | String | 'latest_release', 'latest_snapshot', '1.21.1'. | — | | instance | String | null | Name of the instance if you manage multiple profiles. | — | | detached | Boolean | Detach the Java process from the launcher. | — | | intelEnabledMac | Boolean | Force Rosetta when running on Apple Silicon. | — | | downloadFileMultiple | Integer | Max parallel downloads. | — | | loader.enable | Boolean | Whether to install a mod‑loader (Forge/Fabric/…). | — | | loader.type | String | null | forge, neoforge, fabric, legacyfabric, quilt. | — | | loader.build | String | Loader build tag (e.g. latest, 0.15.9). | — | | loader.path | String | Destination folder for loader files. Defaults to ./loader. | — | | mcp | String | null | Path to MCP configuration for legacy mods. | — | | verify | Boolean | Verify SHA‑1 of downloaded files. | — | | ignored | Array | List of files to skip during verification. | — | | JVM_ARGS | Array | Extra JVM arguments. | — | | GAME_ARGS | Array | Extra Minecraft arguments. | — | | java.path | String | null | Absolute path to Java runtime. | — | | java.version | String | null | Force a specific Java version (e.g. 17). | — | | java.type | String | jre or jdk. | — | | screen.width | Number | null | Width of game window. | — | | screen.height | Number | null | Height of game window. | — | | screen.fullscreen | Boolean | Start the game in fullscreen mode. | — | | memory.min | String | Minimum RAM (e.g. 1G). | ✔︎ | | memory.max | String | Maximum RAM (e.g. 2G). | ✔︎ |

Recommendation: Start with the minimal set (authenticator, path, version, memory) and gradually add overrides only when you need them.

Default configuration

Below is the complete default LaunchOptions object returned by minecraft‑java‑core when you don’t override any field. Use it as a quick reference for every available parameter and its default value.
(Parameters marked nullable can be left null/undefined and the library will figure out sane values.)

const defaultOptions = {
  url: null,                        // Optional custom manifest URL
  authenticator: null,              // Microsoft/Mojang/AZauth profile
  timeout: 10000,                   // Network timeout in ms
  path: '.Minecraft',               // Root directory (alias: root)
  version: 'latest_release',        // Minecraft version (string or 'latest_…')
  instance: null,                   // Multi‑instance name (optional)
  detached: false,                  // Detach Java process from parent
  intelEnabledMac: false,           // Rosetta toggle for Apple Silicon
  downloadFileMultiple: 5,          // Parallel downloads

  loader: {
    path: './loader',               // Where to install loaders
    type: null,                     // forge | neoforge | fabric | …
    build: 'latest',                // Build number / tag
    enable: false,                  // Whether to install the loader
  },

  mcp: null,                        // Path to MCP config (legacy mods)

  verify: false,                    // SHA‑1 check after download
  ignored: [],                      // Files to skip verification
  JVM_ARGS: [],                     // Extra JVM arguments
  GAME_ARGS: [],                    // Extra game arguments

  java: {
    path: null,                     // Custom JVM path
    version: null,                  // Explicit Java version
    type: 'jre',                    // jre | jdk
  },

  screen: {
    width: null,
    height: null,
    fullscreen: false,
  },

  memory: {
    min: '1G',
    max: '2G',
  },
} as const;

Note : Any field you provide when calling Launch.launch() will be merged on top of these defaults; you rarely need to specify more than authenticator, path, version and memory.

Events

| Event Name | Payload | Description | |-------------|---------|--------------------------------------------------------------| | data | String | Raw output from the Java process. | | progress | Number | Global download progress percentage. | | speed | Number | Current download speed (kB/s). | | estimated | Number | Estimated time remaining (s). | | extract | String | Name of the file currently being extracted. | | patch | String | Loader patch currently applied. | | close | void | Emitted when the Java process exits. | | error | Error | Something went wrong. |

Authentication (built‑in)

• Microsoft — OAuth 2 Device Code flow via Xbox Live → XSTS → Minecraft.
• Mojang (legacy) — classic Yggdrasil endpoint.
• AZauth — community Yggdrasil‑compatible server.

The authenticator returns a profile object that you pass directly to Launch.launch().

Utilities

• Downloader — resilient downloader with resume, integrity check & progress/speed events.
• Status — simple TCP ping that returns MOTD, player count & latency.

File structure (simplified)

src/
  Authenticator/       Microsoft, Mojang, AZauth flows
  Minecraft/           Version JSON, assets, libraries, args builder
  Minecraft-Loader/    Forge, NeoForge, Fabric, Quilt, … installers
  StatusServer/        Server ping implementation
  utils/               Downloader & helpers
  Launch.ts            Main entry point
assets/                LWJGL native indexes

Contributors

See the commit history for a full list. Special thanks to:

• Luuxis — original author.
• Community testers & issue reporters.

License

Released under Creative Commons Attribution‑NonCommercial 4.0 International.