Creating Mods for Minecraft in Java
Part 1: Installing what you need
This guide explains how to set up a development environment to allow
you create mods for Minecraft in Java. The instructions are explicitly
designed for Windows. If you need instructions for MacOS or Linux
please ask and we'll update the page.
Below is a step-by-step explanation of what you have to do.
- Download the following files
- The Java SE Development Kit (JDK) from here
- Eclipse, the development tool from here
- 7-Zip, an archive manager from here
- The minecraft_server.jar (NOT the exe) from here
- Rizugami's ModLoader - it's the first mod, about halfway down the page here
- The Minecraft Coder Pack (MCP) which you can find here
- Install the individual pieces
- First install the JDK you downloaded - follow the instructions when you run it.
- Install 7-zip
- Install Eclipse by expanding the downloaded zip file to a directory of your choice
- Unzip the MCP to a directory where you'll create your mods.
- Set up the files. As an example, let's assume that the MCP has been installed into C:\MinecraftMods\MCP, Eclipse has been installed into C:\Program FIles\Eclipse, and the Minecraft Game is installed in C:\Users\MyName\Appdata\Roaming\.minecraft.
- Copy the entire bin and resources folders from your Minecraft game installation into the jars folder under the MCP, i.e. from C:\Users\MyName\Appdata\Roaming\.minecraft to C:\MinecraftMods\MCP\jars.
- Open both the copied minecraft.jar and ModLoader in 7-ZIP. Delete the META-INF folder from minecraft.jar, select the entire contents of ModLoader and drag them into minecraft.jar, answering YES to any questions 7-Zip asks. Close the files, saving the updated minecraft.jar
- Copy the minecraft_server.jar into the jars folder of the MCP.
- Run updatemcp.bat from the MCP folder
- Run decompile.bat from the MCP folder
- Create a shortcut to eclipse.exe and add the parameter -data C:\MinecraftMods\MCP\eclipse to the end of the Target in the shortcut's properties.
This should all be set up at this stage. Launch Eclipse from your
shortcut, and it will show the Client and Server projects. If you expand
these you will see the src folder which contains the Java packages, each
of which contains a number of files which are the decompiled sources for
You are now ready to start creating your first mod.