.JEM File

A JEM file contains entity model information used to alter models in Minecraft with the OptiFine mod tool installed. It stores information about the model in JSON format, which may include the path to a .PNG image that textures the model and information about various parts of the model.

JEM file open in Microsoft Notepad

You will most likely only encounter a JEM file if you are looking to alter the appearance of entities in Minecraft with the Optifine optimization mod installed. Some entities that Minecraft users modify include cows, creepers, dragons, chickens, books, and chests.

If you are looking to override an entity model, you can place the JEM file in the following directory in the resource pack:

assets/minecraft/optifine/cem

Once the JEM file is placed in the directory, the model will appear in Minecraft as long as the OptiFine optimization mod is installed.

How do I open a JEM file?

You can open and edit JEM files with various model editors, such as Blockbench and Cubik Studio. These tools allow you to visualize the model while you edit JEM files.

Since JEM files are saved in plain text in JSON format, you can also open and edit the files with text editors. Keep in mind that you will not be able to view the models when editing them.