Your First Pack

Create A Project

cobble init --name my_datapack
cd my_datapack

This writes cobble.toml, src/main.cbl, and a .gitignore. cobble init --list-templates shows the other starter templates.

Write Some Code

Replace src/main.cbl with:

from stdlib import event

def on_load():
    /tellraw @a {"text":"Hello from Cobble!", "color":"green"}

def reward(player, amount):
    /give {player} minecraft:diamond {amount}

stdlib.addEventListener(event.LOAD, on_load)

on_load runs whenever the pack loads. reward takes two parameters, so it becomes a macro function.

Build

cobble build --validate

The pack is written to output/. --validate checks every generated command against the Minecraft 26.3 command tree; leave it out for a quick build. cobble check reports source errors without building.

Load It In Minecraft

Copy or build the pack into a world’s datapacks/ folder:

cobble build -o ~/.minecraft/saves/MyWorld/datapacks/my_datapack

~/.minecraft is the Linux location. On Windows it is %APPDATA%\.minecraft ($env:APPDATA\.minecraft in PowerShell), and on macOS ~/Library/Application\ Support/minecraft.

Then, in the world:

/reload
/datapack list
/function my_datapack:reward {player:"@s", amount:3}

/datapack list shows the pack as enabled. To turn it off or on, use /datapack disable "file/my_datapack" and /datapack enable "file/my_datapack".

Rebuild On Save

cobble link --world ~/.minecraft/saves/MyWorld
cobble watch --link

cobble link saves the world’s datapacks/ folder for this project, and cobble watch --link rebuilds into it whenever a source file changes. Run /reload in game to pick up each build.

If Something Goes Wrong

The pack is missing from /datapack list. Check that the folder is directly under datapacks/ and contains pack.mcmeta, and that the world runs Minecraft 26.3.
A function is not found. Run /reload after building, and call it with the project namespace, such as my_datapack:on_load.
Changes do not appear. Check that the build went to the world you have open, then /reload.
Variables look wrong. Cobble keeps numeric variables on the <namespace>.vars objective: /scoreboard players get <name> my_datapack.vars.

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