KubeJS
Edit recipes, add new custom items, script world events, all in JavaScript!
About this Mod
KubeJS
What does this mod do?
This mod lets you create scripts in JavaScript language to manage your server, add new blocks and items, change recipes and tags, add custom handlers for quest mods, change worldgen and more!
How to use it?
Run the game with mod installed once. It should generate kubejs folder in your minecraft directory with example scripts. startup scripts only get run once when the game loads. Those are for registering items, setting up configs etc. Server/data scripts are loaded when you join a world, those are better for things like clearlag, displaying custom login messages and world/player related things in general.
Video tutorial for 1.19.2
Can I reload scripts?
Yes, use /reload. Note: Not everything is reloadable. Some things require you to restart game, some only world, some work on fly.
I don't know JavaScript / I need help with this mod!
There's examples and pre-made scripts on KubeJS Wiki.
I have a question / suggestion / bug report!
If wiki didn't have the answer for what you were looking for, you can ask questions, make feature suggestions and report bugs here: KubeJS Support
Available Versions
How to Install KubeJS on Your Server
Order Server
Order a Minecraft Java server with at least 3 GB RAM (4 GB recommended).
Set fabric Loader
In the panel under "Egg", select the fabric loader and matching Minecraft version (26.1.2).
Install Mod
Open the mod browser in the dashboard and search for "KubeJS". Click "Install" – done! Alternatively, upload the .jar via SFTP to the /mods folder.
Compatibility
Mod Loaders
Minecraft Versions
26.1.2, 1.21.1, 1.21 (+5 more)
Server-side
~ OptionalRecommended RAM
4 GB(min. 3 GB)Frequently Asked Questions
KubeJS server crashes on startup – what to do?
Most common cause: wrong fabric version or insufficient RAM. Check the server log (latest.log) for "OutOfMemoryError" or "Mixin" errors. With Mado Hosting: ensure at least 3 GB RAM is allocated and the loader matches the mod version (26.1.2). You can switch loaders with one click in the panel.
Is KubeJS compatible with fabric and forge and neoforge and quilt?
KubeJS officially supports fabric, forge, neoforge, quilt for Minecraft 26.1.2, 1.21.1, 1.21. Note: Forge and Fabric mods are NOT cross-compatible – pick one loader and stick with it. The Mado dashboard automatically detects incompatible loader combinations.
Server lagging with KubeJS – how to optimize performance?
Recommended RAM: 4 GB (per 8 players). Use /spark profiler to check if KubeJS consumes the most tick time. Common fixes: reduce server view-distance to 8-10, install "performant" or "starlight" as supplementary mods on Forge. With Mado Hosting, your server runs on NVMe SSDs with dedicated CPU cores for minimal latency.
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Install KubeJS with just one click on your server.