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A mod manager for The Legend of Zelda: Breath of the Wild

Project description


BCML: BOTW Cross-Platform Mod Loader

A mod merging and managing tool for The Legend of Zelda: Breath of the Wild

BCML Banner


Why a mod loader for BOTW? Installing a mod is usually easy enough once you have a homebrewed console or a emulator. Is there a need for a special tool?

Yes. As soon as you start trying to install multiple mods, you will find complications. The BOTW game ROM is fundamentally structured for performance and storage use on a family console, without any support for modification. As such, files like the resource size table or TitleBG.pack will almost inevtiably begin to clash once you have more than a mod or two. Symptoms can include mods simply taking no effect, odd bugs, actors that don't load, hanging on the load screen, or complete crashing. BCML exists to resolve this problem. It identifies, isolates, and merges the changes made by each mod into a single modpack that just works.


  • Windows 10 (7-8 might work but are not supported) or basically any modern Linux distribution
  • A legal, unpacked game dump of The Legend of Zelda: Breath of the Wild for Switch (version 1.6.0) or Wii U (version 1.5.0)
  • The latest x64 Visual C++ redistributable
  • Cemu (optional)


There are three ways to install BCML.


Install Python 3.7+ (64 bit version), making sure to add it to your PATH, and then run pip install bcml. Note that, because of the cefpython3 dependency, on Windows only Python 3.7 is supported, but 3.8+ can be used on Linux.

Windows Installer

Download the setup executable from the latest GitHub release or from GameBanana. Double click to run and install BCML. Note: You can install wherever you like, but if you install to a location that required administrator permissions, you may run into complications down the line. Simply C:\BCML is often a good choice.

Building from Source

Building from source requires, in addition to the general prerequisites:

  • Python 3.7+ 64 bit

  • Node.js v14

  • The following Python packages:

    • aamp>=1.4.1
    • byml>=2.3.1
    • oead>=1.1.1
    • mkdocs>=1.1.2
    • mkdocs-material>=5.4.0
    • pyYaml~=5.3.1
    • requests~=2.23.0
    • rstb>=1.2.0
    • setuptools~=46.4.0
    • xxhash~=1.4.3
    • wheel~=0.34.2

Steps to build from source:

  1. Prepare the webpack bundle

    1. Open terminal to bcml/assets
    2. Run npm install
    3. Run npm build (or npm test to watch while editing)
  2. Build the docs

    1. Open terminal to repo root folder
    2. Run mkdocs build -d bcml/assets/help
  3. Install BCML with python install or run without installing with python -m bcml

Usage and Troubleshooting

For information on how to use BCML, see the Help dialog in-app or read the documentation on the repo. For issues and troubleshooting, please check the official Troubleshooting page.


BOTW is an immensely complex game, and there are a number of new mergers that could be written. If you find an aspect of the game that can be complicated by mod conflicts, but BCML doesn't yet handle it, feel free to try writing a merger for it and submitting a PR.


This software is licensed under the terms of the GNU General Public License, version 3 or later. The source is publicly available on GitHub.

This software includes the 7-Zip console application 7z.exe and the library 7z.dll, which are licensed under the GNU Lesser General Public License. The source code for this application is available for free at

This software includes a lightly modified copy of the console application msyt.exe by Kyle Clemens, copyrighted 2018 under the MIT License. The source code for this application is available for free at The only change is a replacement of serde_yaml with serde_json.

This software includes part of a modified copy of the pywebview Python package, copyright 2020 Roman Sirokov under the BSD-3-Clause License. The source code for the original library is available for free at

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