How to Make a Minecraft Mod: Fabric Projects, Java Code, and JAR Building

This guide covers creating a mod that outputs a log on its first run, based on Minecraft Java Edition 26.2 and Fabric. It is an introductory example to follow up to the point where the mod file is recognized by the loader and your written Java code executes. Because the structure differs from Bedrock add-ons and Forge/NeoForge projects, do not mix them in a single project.

1. Preparing the Development Environment

The current 26.2 documentation for Fabric recommends JDK 25. Instead of installing only the Java runtime environment, install the development JDK and prepare IntelliJ IDEA or VS Code. Check the currently used Java in your terminal with the command below. The IDE's Project SDK and Gradle JVM must also point to the same version. To create for older versions such as 1.21.1, change the version selection at the top of the documentation and the generator version together, and follow the JDK requirements of that version.

java -version
javac -version

2. Creating a Project in the Fabric Generator

1. Open the official Fabric Template Mod Generator.
2. Set the Mod Name to TroubleMaker Hello, the Mod ID to tmhello, and the Package Name to com.ascgame.tmhello.
3. Match the Minecraft version to 26.2. Advanced options like Kotlin or separate data generation do not need to be added in the first example.
4. Download the ZIP and extract it to a simple path like C:/Projects/TMHello. Determine the project folder according to your actual operating system.
5. Open build.gradle or the project root in your IDE and wait for Gradle importing to finish. Keep the Loader, Loom, and API versions determined by the generator as they are.

3. Understanding What the Files Do

src/main/java is for common Java code, src/main/resources/fabric.mod.json declares the mod ID, entry class, and dependencies, and gradle.properties handles version and project settings. Depending on the generator, client code may be separated into src/client/java. This example changes only the common initialization code. Do not arbitrarily delete all configuration files or overwrite them with settings for other versions found on the internet.

4. Writing Your Initialization Class

Find the generated common ModInitializer implementation file and modify it to the structure below. If you renamed the file to TMHello.java, make sure the package folder and class name match as well. Since SLF4J logging is used, you can verify initialization without item registration APIs that are prone to changing across different game versions.

package com.ascgame.tmhello;

import net.fabricmc.api.ModInitializer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class TMHello implements ModInitializer {
    public static final String MOD_ID = "tmhello";
    private static final Logger LOG = LoggerFactory.getLogger(MOD_ID);

    @Override
    public void onInitialize() {
        LOG.info("TroubleMaker: my first Fabric mod is ready.");
    }
}

While keeping the rest of fabric.mod.json, ensure that entrypoints.main points to the full name of the class above. Below is the part to check, not the entire file. Do not replace existing mixins or client configurations entirely.

{
  "entrypoints": {
    "main": ["com.ascgame.tmhello.TMHello"]
  }
}

5. Development Execution and Final File Building

1. At the project root, run gradlew.bat runClient on Windows or ./gradlew runClient on macOS/Linux.
2. Search for the TroubleMaker phrase in the development client console or run/logs/latest.log. This is an example that outputs once during initialization before entering a world.
3. Close the game and create the distribution file using gradlew.bat build on Windows or ./gradlew build on macOS/Linux.
4. Check the general distribution JAR in build/libs. Do not use development files with sources or dev appended to their names as general distributions.
5. Place the JAR into the mods folder of a separate Fabric instance for the same Minecraft version. If Fabric API is in the generated dependencies, install it matching the same version.
6. Run it with the actual launcher and verify that the same phrase is printed in the instance's logs/latest.log.

6. Common Errors and Recovery

For Unsupported class file version, check the Java version first; for entry class loading errors, check mismatches in package, class name, and entrypoints. If it is silent after placing it in the mods folder, check whether you put it in a different launcher instance. Since this example does not add save data, you can exit the game and remove the JAR to compare. When adding items or blocks later, continue reading the Fabric First Item documentation for the target version, and match the file paths and registration APIs to that version.

7. Information to Include When Sharing

Write the mod ID, supported Minecraft versions, Loader and Fabric API conditions, JDK requirements, and example features and removal methods in the README. Separate the source code and the distribution JAR, and do not include the game executable or other creators' mod files. For the initial version, verify that the logs output correctly in the actual general launcher, then distribute it with a version number like 1.0.0.

Original Documents and Verification Criteria

This introductory guide was written by the TroubleMaker operations team, verified against creator and official tool documents on October 7, 2026. The code and diagrams are custom examples for explanation purposes and do not represent the verified results of actual gameplay of the game on this server. Verify and distribute using a separate test save with the version specified in the text. Compare the latest versions and dependencies for each tool using the original sources below.

Fabric 개발 환경

Fabric 프로젝트 생성

Fabric 모드 빌드

Fabric 공식 생성기