How Minecraft Mods Are Packed Internally

A technical breakdown of how Forge and Fabric Minecraft mods are structured inside their JARs — mixins, assets, lang files, bytecode transformers, and obfuscation mappings.

The Container: A JAR Within a Game's Classpath

Mod Metadata: mods.toml and fabric.mod.json

Class Files: Your Mod's Logic

Mixins: Bytecode Surgery

Assets: Textures, Models, Sounds, Localizations

Data: Recipes, Loot Tables, Advancements

Obfuscation and Remapping

What You Can Safely Change