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Setup

Prerequisites

You will need:

  • Java Development Kit Version 16 or newer
  • IntelliJ IDEA
  • Intermediate Java knowledge
  • Git and basic git experience
  • The Minecraft Development plugin for IntelliJ
  • Basic JSON knowledge

Download

Create a new repository, either locally or on GitHub/GitLab. If you did not create it locally, go to file -> new from version control and clone the repo

Download the code from the Fabric example mod repo. You will then need to copy the contents into your repository folder.

Note about the Minecraft Development Plugin

While you can handle the initial setup with the plugin, it has major bugs when it comes to 1.17 mod setup. You will also gain experience with Gradle and Loom this way

Initialise your mod

First, open up the gradle.properties file within IntelliJ. It will look something like this:

# Done to increase the memory available to gradle.
org.gradle.jvmargs=-Xmx1G

# Fabric Properties
    # check these on https://fabricmc.net/versions.html
    minecraft_version=1.17.1
    yarn_mappings=1.17.1+build.14
    loader_version=0.11.6

# Mod Properties
    mod_version = 1.0.0
    maven_group = com.example
    archives_base_name = fabric-example-mod

# Dependencies
    fabric_version=0.37.0+1.17

First, you want to delete the dependencies section of your gradle.properties file.

Open up the fabric versions page in your browser.

Replace your # Fabric Properties section with the gradle.properties values found on the versions page.

Next, you need to set your mod information.

Set maven_group to io.github.yourusername and set archives_base_name to the name of your mod, in lower-case letters and without spaces.

Fabric setup

Now we have our Gradle set up, you will need to tell fabric about your mod. Navigate to your fabric.mod.json file found under src/main/resources

It will look something like this:

{
  "schemaVersion": 1,
  "id": "modid",
  "version": "${version}",

  "name": "Example Mod",
  "description": "This is an example description! Tell everyone what your mod is about!",
  "authors": [
    "Me!"
  ],
  "contact": {
    "homepage": "https://fabricmc.net/",
    "sources": "https://github.com/FabricMC/fabric-example-mod"
  },

  "license": "CC0-1.0",
  "icon": "assets/modid/icon.png",

  "environment": "*",
  "entrypoints": {
    "main": [
      "net.fabricmc.example.ExampleMod"
    ]
  },
  "mixins": [
    "modid.mixins.json"
  ],

  "depends": {
    "fabricloader": ">=0.11.3",
    "fabric": "*",
    "minecraft": "1.17.x",
    "java": ">=16"
  },
  "suggests": {
    "another-mod": "*"
  }
}

This files holds all the metadata about our mod, which Fabric uses to load the mod. Here is a list of fields and what you should change them to:

id: The same value as you put for archives_base_name in gradle.properties.

name: The formatted name of your mod. This can include spaces and capital letters.

description: A short, formatted description of your mod

authors: [ "your_username" ]

Fill out the contact section with your relevant links, but you can remove it if you would like.

license: The name and potentially version of the license of your choice. Although we strongly discourage keeping mods closed source, you may indicate this by omitting the field.

environment: Leave at * if you want your mod to work on singleplayer (might cause issues), otherwise change it to server

suggests: Feel free to remove this section

depends: Will be covered in a tutorial showing how to use mod libraries. You can leave it as the default for now

modid.mixins.json: Change it to <your_modid>.mixins.json

You will also need to rename the modid.mixins.json file to <your_modid>.mixins.json, in your src/main/resources folder.

Mixin file

Your <your_modid>.mixins.json file should look like this:

{
  "required": true,
  "minVersion": "0.8",
  "package": "net.fabricmc.example.mixin",
  "compatibilityLevel": "JAVA_16",
  "mixins": [
  ],
  "client": [
    "ExampleMixin"
  ],
  "injectors": {
    "defaultRequire": 1
  }
}

Replace the net.fabricmc.example with your mod package, rename the client block to server and delete the "ExampleMixin" entry.

Entrypoints

Entrypoints are the classes where Fabric starts your mod - a piece of code that runs on game launch. More information can be found on the fabric wiki page.

Dedicated server only

Change the main entry in your entrypoints section to server

You must now determine your package. This will most likely be the maven_group value from your gradle.properties, but with the name of your main class appended. An example would be: io.github.username.modname.ModName.

After specifying this value, we now need to actually create the entrypoint. Delete the net folder found under src/main/java.

Create a folder structure with your package, within the src/main/java directory. io.github.username.modname would become io/github/username/modname.

Once you have created this folder, right click it in IntelliJ and press "Create Java class". The class name should be the value after your package specified in the entrypoints section. In the example case, it would be ModName.

Just one more step now - we need to get Fabric to recognise our main class. Make the class you just created implement DedicatedServerModInitializer if you are targeting dedicated server only, or ModInitializer if you support singleplayer. Add System.out.println("MOD LOADED") to the overridden method IntelliJ should prompt you to make.

Run configurations

Go to the top right-hand corner of IntelliJ, press "Add Configuration", then under "application" you will find Minecraft Server. Select that and press debug. You will need to agree to the EULA, but if all goes well your mod has been loaded!

Export

In the Gradle tab, choose build. You want the jar without -dev or -sources found in build/libs