Check your computer before you start

Minecraft modding needs Java 21, IntelliJ IDEA, Fabric and a copy of Minecraft Java Edition. Go through this list first and setup will take minutes instead of a full session.

Lumo's outcome check

What you'll finish with

Your project
Minecraft Modding: Check Your Computer Before You Start
You'll learn
Minecraft modding needs Java 21, IntelliJ IDEA, Fabric and a copy of Minecraft Java Edition. Go through this list first and setup will take minutes instead of a full session.
Finish with
a working setup you can build on
Then extend it
using it as the starting point for your own project
⚠️ Minecraft Java Edition only

This course uses Minecraft Java Edition (the paid PC/Mac version). Minecraft Bedrock (Windows 10 edition, console, mobile) is a different game and uses a completely different modding system. If you have Bedrock, the workshops will not work. Check your launcher: it should say Java Edition.

☑️ Setup checklist

Go through each item before your first workshop session. Items marked Teacher are worth completing before the learner arrives.

  • ☕
    Java JDK 21 is installed Open a terminal and type java -version. You should see openjdk version "21...". If not, download Temurin 21 from adoptium.net (free). During install, tick "Add to PATH" if asked.
  • 💡
    IntelliJ IDEA (Community Edition) is installed Download the free Community Edition from jetbrains.com/idea. This is the editor used for every workshop in the course. It is a large download (about 750 MB) so allow time before the session.
  • 🧱
    Minecraft Java Edition is installed and you can launch it Open the Minecraft Launcher and confirm it says "Java Edition". Run the game at least once before the workshop so all game files are fully downloaded.
  • 💾
    At least 5 GB of free disk space Minecraft, IntelliJ, the JDK and the Fabric mod template together need around 3-4 GB. Gradle will also download dependencies the first time you build, adding another 500 MB. Tight disk space is the most common cause of failed builds.
  • 🔒
    You can install software on this computer You need admin/install rights for Java JDK and IntelliJ. On a school computer this is often blocked. If you are unsure, ask your IT team or a parent before the session starts.
  • 🌐
    The computer can reach adoptium.net and github.com Gradle downloads the Fabric template from GitHub on first build. If your school or home network blocks GitHub or Maven repositories, the first build will hang or fail. Test this before the session by opening github.com in a browser.
  • 📦
    The Fabric mod template opened and built without errors Episode 1 walks through this step by step, but it is worth testing in advance. Open IntelliJ, clone or download the Fabric example mod template from GitHub, and run the Gradle build once. A clean build confirms Java, IntelliJ and the internet connection all work together.

👩‍🏫 Advice for teachers and parents

📋 Do the setup before the learner arrives

Setup (Java, IntelliJ, first Gradle build) takes 20-40 minutes on a good connection. On a restricted school network it can take a full session. Do every step on this checklist yourself first, on the learner's computer, before their timed lesson begins.

  • Use a home or hotspot internet connection for the initial Gradle download if the school network blocks Maven or GitHub.
  • Run the Minecraft Launcher once with the student's account so the game files download fully.
  • IntelliJ's first-run setup and plugin downloads can take several minutes - complete these before the session.
  • If your school uses a firewall or proxy, test adoptium.net, github.com and repo1.maven.org before the session. Blocked repos are the most common classroom failure point.

🔧 Common errors and fixes

💡 Most errors happen during the first Gradle build

Once you have a clean build the rest of the course runs smoothly. Work through the fixes below if the build fails. If you are stuck, the Modding Cheatsheet has a quick-reference for common command errors.

Error or symptom Likely cause Fix
java is not recognised Java not on PATH Reinstall JDK 21 from adoptium.net and tick "Add to PATH" during install. Restart your terminal after.
Wrong Java version shown Old Java version active Set JAVA_HOME to your JDK 21 folder. In Windows: System Properties > Environment Variables > new JAVA_HOME entry.
Gradle build hangs at "Downloading..." Firewall or proxy blocking Maven/GitHub Try on a different network (home or mobile hotspot). If on a school network, ask IT to allow outbound HTTPS to repo1.maven.org, maven.fabricmc.net and github.com.
Could not resolve com.mojang:minecraft Minecraft not launched yet Open the Minecraft Launcher, run Java Edition once, then try the Gradle build again.
Disk quota exceeded or build fails with no clear message Not enough disk space Free up at least 5 GB. Empty the Recycle Bin. Delete any unused large files. Run the build again.
IntelliJ says "No JDK found" IntelliJ not pointing to JDK 21 In IntelliJ: File > Project Structure > Project > SDK. Click "Add SDK" and point it to your JDK 21 folder (usually C:\Program Files\Eclipse Adoptium\jdk-21...).
Access denied or installer fails silently No admin rights Right-click the installer and choose "Run as administrator". On a school computer, ask IT for help.

Ready? Start Episode 1

Everything checks out. Head to Episode 1 to install Fabric and add your first custom item to Minecraft.

Go to Episode 1 - Hello Minecraft! →