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Inner Core Toolchain Guide


Inner Core for Horizon toolchain is a toolchain that can be used to efficiently develop and build mods from your PC.

To work properly this toolchain requires:

  • Python 3.6 or higher
  • node.js 10.15.1 or higher (for typescript modding), you need to have tsc installed (to install run npm install -g tsc)
  • Valid Android NDK installation (for native modding). Preferred version is r16b
  • Java Development Kit 1.8 or higher (for Java modding)

It is also highly recommended you install Visual Studio Code code editor. This editor is highly customizable and this toolchain contains all required settings and files to set up the environment. For the best user experience also install the following plugins for VS Code:

  • TSLint (Microsoft)
  • C/C++ (Microsoft)
  • Java Extension Pack (Microsoft)

You can find detailed explanation about how to set up all the requirements in this video: Inner Core/Horizon Mods Development | Setting up the Environment

Linux version

Here is a fork of toolchain to run under linux: link

Creating a new project

To create a new project for Inner Core, use the script It should be placed in your projects directory and run using python:

python .\ project_folder

The script will create a new project and set it up for native and/or java development. See detailed explanations in the video: Inner Core/Horizon Mods Development | Creating and Importing Projects

Importing existing project

To create a project from an existing Inner Core mod, use the script It should be placed in the mod directory and run using python:

python .\

You can optionally pass old project directory as the first parameter of the script. This script will create required project structure and optionally set up the project for native and/or java development.

Installing Android NDK

To install Android NDK of any version on you computer, you should first download it from the archive: Preferred version is 16b. Unpack the archive to %appdata%/../Local/Android (on Windows) or to /home/Android (on Linux). When you open the directory "Android/android-ndk-r16b", you should see a list of directories. Run the build to see if everything is OK.

First Build

To run your first build, run (Ctrl+Shift+B) Build and Push Everything task. This task performs the required setup and builds the whole project. If your project contains native code, local NDK installation will be created. This can take some time.


make.json is the main configuration file of the project. In this file you can specify everything you need to build a mod for Inner Core. Most of the work, such as scripts generation and build.config creation is done under the hood.

Here's a description of some of the key properties you can specify in your make.json:

  • contains information about the mod name, author, version and description. The information is stored in the corresponding fields
  • global.api specifies what JavaScript API is used in the mod by default
  • make contains information about what libraries should be linked and what ABIs should the project target. You generally don't want to change these settings
  • resources specifies what resources should be included in the output mod. There are currently four resource types available:
    • resource_directory contains textures to use in Minecraft
    • gui contains all the gui textures
    • minecraft_resource_pack contains vanilla resource packs to be used with the mod
    • minecraft_behavior_pack contains vanilla behavior packs to be used with the mod
  • sources specifies what JavaScript files should be included (or built) into the mod build. Every source can be a file, a list of files specified by wildcards or a directory containing .includes file. There are currently four types of sources:
    • main contains main mod logic
    • launcher contains mod launching logics
    • preloader is run before resources injection. This is useful to generate resources programmatically before Minecraft loads them
    • lib contains reusable mod libraries
  • There are also two supported languages:
    • javascript is used for pure javascript project using ES5 language standart. These folders are not compiled and are just built 'as is'.
    • typescript is used for typescript language and ESNext version of Javascript. These folders are built using typescript compiler.
  • compile specifies all the source code that should be compiled. This toolchain currently supports two compilation types:
    • native is used to compile C/C++ sources. Note that Android NDK is required to run this type of compilation
    • java is used to compile Java sources. Note that you have to install JDK of version 1.8 or higher to run this type of compilation
  • additional contains additional directories that should be copied to the mod build. In this example, root directory is copied to the root of the mod

Documentation and Further Resources

All the documentation is available at

Some of the old (but mostly still applicable) information can be found at

To update your local typescript header files (used for hints in JavaScript files), go to, download everything from toolchain/jslibs and unpack to your local toolchain/jslibs folder. The documentation is a subject to regular updates, so be sure to use the latest features it provides 😉

Adding Java directories

By default this toolchain doesn't contain java modules to minimize build time. However, if you need to include a java module into your mod, follow the instructions below.

Unpack archive to the root of mod source. You will get the following files structure:

└─ src
   └─ java
   │  └─ sample
   │     ├─ lib
   │     ├─ src
   │     │  └─ com
   │     │     └─ sample_mod
   │     │        └─ sample_package
   │     │           └─
   │     └─ manifest
   └─ .classpath

In the example above, a sample java module is already created. To add a new one, create a directory in java folder and add it to .classpath file as a new entry:

<classpathentry kind="src" path="src/java/module_name/src"/>

To add .jar libraries to classpath and to the compiler, move your library file to the libs directory and add a new entry to the .classpath file:

<classpathentry kind="lib" path="src/java/sample/lib/lib_name.jar"/>

Working with Android Debug Bridge

Android Debug Bridge allows this toolchain to push mod files to the remote device and to launch Horizon via USB cable. You can specify push path in the make.pushTo property in your make.json. When you run the appropriate build task (Ctrl+Shift+B), only the files that were changed are being pushed.

Building and Publishing a Release Version of the Mod

To build a release version of the mod, run Assemble Mod for Release task. An .icmod archive is being generated and is ready for upload. Go to and upload a new mod or update an existing one.


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