Minecraft wiki entry for Creating_Forge_mods, associated text: If you have been playing Minecraft Java Edition, you probably already have JRE (Java Runtime Environment). To develop a mod, you will need to find JDK (Java Development Kit), which includes the JRE and an emulator. Create a free account at oracle.com and download JDK Standard Edition version 8. Then follow the instructions for installing it, and make note of the location it installs to. Pay particular attention to the section on Updating the PATH Environment Variable.