This project is near complete.

MCLC is a NodeJS solution for launching modded and vanilla Minecraft without having to download and format everything yourself. Basically a core for your Electron or script based launchers.

Getting support

Since people seem to use this, I've created a Discord server for anyone who needs to get in contact with me or get help! https://discord.gg/8uYVbXP

Installing

npm i minecraft-launcher-core

Standard Example

const { Client, Authenticator } = require('minecraft-launcher-core');

let opts = {
    clientPackage: null,
    authorization: Authenticator.getAuth("username", "password"),
    root: "./minecraft",
    os: "windows",
    version: {
        number: "1.14",
        type: "release"
    },
    memory: {
        max: "6000",
        min: "4000"
    }
}

const launcher = new Client();
launcher.launch(opts);

launcher.on('debug', (e) => console.log(e));
launcher.on('data', (e) => console.log(e));
launcher.on('error', (e) => console.log(e));

Documentation

Client Functions

Function	Type	Description
launch	Promise	Launches the client with the specified options as a parameter. Returns child the process

launch

Parameter	Type	Description	Required
options.clientPackage	String	Path to the client package zip file.	False
options.root	String	Path where you want the launcher to work in. like C:/Users/user/AppData/Roaming/.mc,	True
options.os	String	windows, osx or linux. MCLC with auto determine the OS if this field isn't provided.	False
options.version.number	String	Minecraft version that is going to be launched.	True
options.version.type	String	Any string. The actual Minecraft launcher uses release and snapshot.	True
options.memory.max	String	Max amount of memory being used by Minectaft.	True
options.memory.min	String	Min amount of memory being used by Minectaft.	True
options.forge	String	Path to Universal Forge Jar.	False
options.javaPath	String	Path to the JRE executable file, will default to java if not entered.	False
options.server.host	String	Host url to the server, don't include the port.	False
options.server.port	String	Port of the host url, will default to 25565 if not entered.	False
options.proxy.host	String	Host url to the proxy, don't include the port.	False
options.proxy.port	String	Port of the host proxy, will default to 8080 if not entered.	False
options.proxy.username	String	Username for the proxy.	False
options.proxy.password	String	Password for the proxy.	False
options.timeout	Integer	Timeout on download requests.	False
options.window.width	String	Width of the Minecraft Client	False
options.window.height	String	Height of the Minecraft Client.	False

Note

If you are loading up a client outside of vanilla Minecraft or Forge (Optifine and for an example), you'll need to download the needed files yourself if you don't provide downloads url downloads like Forge and Fabric. Still need to provide the version jar.

Authenticator Functions

getAuth

Parameter	Type	Description	Required
username	String	Email or username	True
password	String	Password for the Mojang account being used if online mode.	False

validate

Parameter	Type	Description	Required
access_token	String	Token being checked if it can be used to login with (online mode).	True

refreshAuth

Parameter	Type	Description	Required
access_token	String	Token being checked if it can be used to login with (online mode).	True
client_token	String	Token being checked if it's the same client that the access_token was created from.	True
selected_profile	Object	Json Object that was returned from Mojangs auth api.	True

invalidate

Parameter	Type	Description	Required
access_token	String	Token being checked if it can be used to login with (online mode).	True
client_token	String	Token being checked if it's the same client that the access_token was created from.	True

signOut

Parameter	Type	Description	Required
username	String	Username used to login with	True
password	String	Password used to login with	True

Events

Event Name	Type	Description
arguments	Object	Emitted when launch arguments are set for the Minecraft Jar.
data	Buffer	Emitted when information is returned from the Minecraft Process
close	Integer	Code number that is returned by the Minecraft Process
error	String	Emitted when the Minecraft Process errors
package-extract	null	Emitted when clientPackage finishes being extracted
download	String	Emitted when a file successfully downloads
download-status	Object	Emitted when data is received while downloading
debug	String	Emitted when functions occur, made to help debug if errors occur

What should it look like running from console?

Showing the emitted information from debug and data, also using getPid after the process has been created.