Simple minecraft launcher and version manager

Usage no npm install needed!

<script type="module">
  import jmcl from '';



A simple minecraft launcher and version manager running on node. Allows you to launch or download Minecraft with one simple command!

Command line usage


jmcl launch -u <uname> -v <version of minecraft to be launched> 

It will prompt you to enter password if this is first run, where <uname> is the email address of your Mojang(Yggrasil) account.

Add --offline option to launch in offline mode, in which case <uname> should be in-game user name. Should I remove this option to support Mojang?

To open a local TCP server and write all log output of Minecraft to it, add option --pips [<port>]. See webmc for more detail.


jmcl logout -u <your email>

Game installing and deleting

Install Minecraft version specified by <version>:

jmcl install <version>

It will do library and assets file checking if already installed, that is, download missing files and re-download files with bad check sums. To do this check for all installed versions, run

jmcl install-all

Sometimes the version file contains no check sum informations, this only happen to third party clients, not Vanilla. In this case there's no way to check their validity, so these files won't be re-downloaded if they are not missing. You may add --redownload option to the above two commands to force re-download all files that has no check sum information.

To delete a verion:

jmcl remove <version>

This would only remove the main jar package and version file. If you want to delete unnecessay libraries and asset files, you may want to use

jmcl cleanup

which will delete all game files that aren't used by any installed versions.

In addition, use

jmcl list

to list all installed versions, and

jmcl list-all

to view all available versions. Add --release option to list only release versions.

Fabric, Optifine support

Just first install with their officially provided launcher and then you can launch them with jmcl. If you don't know their version name, run jmcl list. But since their version file contains no check sums, you have to use --redownload option if any library file get corrupted, such as a download failure.


I'm sorry that Forge isn't fully supported. Although you can install and launch it the same way as Fabric and Optifine, the libraries listed in its version file is not all the libraries of it. So Forge installation will be corrupted if you run jmcl cleanup. I'm still working on the workarround.


  • Forge support.