carbon.mod.json — Full Specification

carbon.mod.json is the metadata file for every mod in the Carbon ecosystem. It must be placed at the root of the mod zip. It is also used by Fabric mods that hook into Allotrope, making it the single standardized format across the entire Carbon Loader ecosystem.

---

Minimal Example (Carbon Mod)

{
  "id": "ruby_mod",
  "name": "Ruby Mod",
  "version": "1.0.0",
  "authors": ["zleo"],
  "description": "Adds ruby items and a weak skeleton mob.",
  "icon": "resources/textures/icon.png",
  "minecraft_version": "1.21",
  "type": "carbon",
  "dependencies": []
}

---

Full Example (Allotrope Mod — both parent and child)

{
  "id": "my_allotrope_mod",
  "name": "My Allotrope Mod",
  "version": "1.0.0",
  "authors": ["yourname"],
  "description": "Injects into both the Parent and Child loaders.",
  "icon": "resources/textures/icon.png",
  "minecraft_version": "1.21",
  "type": "allotrope",
  "dependencies": [],
  "allotrope": {
    "inject_parent": true,
    "inject_child": true,
    "mixins": {
      "parent": [
        "src/stubuiaddon.cj"
      ],
      "child": [
        "src/guifix.cj"
      ]
    }
  }
}

---

Allotrope Mod — Child Only (flat list shorthand)

If only injecting into the child, mixins can be a flat list. Carbon defaults to child injection when no parent/child split is specified.

{
  "id": "guifix",
  "name": "GUI Fix",
  "version": "1.0.0",
  "authors": ["yourname"],
  "minecraft_version": "1.21",
  "type": "allotrope",
  "allotrope": {
    "inject_parent": false,
    "inject_child": true,
    "mixins": [
      "src/guifix.cj"
    ]
  }
}

---

Field Reference

Field	Required	Description
id	Yes	Unique mod ID. Lowercase, underscores only. Used as namespace.
name	Yes	Display name shown in mod list.
version	Yes	Semantic version string, e.g. "1.0.0"
authors	Yes	Array of author names.
description	No	Short description of the mod.
icon	No	Path to icon image inside the zip.
minecraft_version	Yes	Target Minecraft version, e.g. "1.21"
type	Yes	See Type Values below.
dependencies	No	Array of mod IDs this mod requires.
allotrope	Only for allotrope type	Mixin injection config.

---

Type Values

Type	Description
"carbon"	A standard Carbon Lang Script mod.
"allotrope"	Injects Java into Carbon Loader via mixins.
"fabric"	A Fabric mod that uses carbon.mod.json for Carbon ecosystem compatibility.

---

allotrope Block Fields

Field	Description
inject_parent	true if this mod injects into the ParentLoader.
inject_child	true if this mod injects into the ChildSession/Knot.
mixins	Either a flat array (defaults to child) or an object with "parent" and "child" arrays.

---

Mixin Routing Rules

• Flat array → all files routed to child.
• Object with "parent" and "child" keys → explicitly routed.
• A file can appear in both "parent" and "child" if it targets a shared handoff class.
• If a file targets the wrong classloader's classes, Carbon throws an error at load time and the mod does not load.

---

Dependencies

"dependencies": [
  "carbon_lib",
  "sodium",
  "my_other_mod"
]

Dependencies are resolved automatically. If a listed dependency is missing, Carbon auto-fetches it from Modrinth before launching. The key "carbonloader" is also accepted as a dependency identifier.