Overview
Blindfold Chess uses open source chess engines to provide its AI opponent functionality. We are grateful to the authors and communities behind these projects, and we provide attribution and license information below.
Bundled Open Source Components
The following components are bundled with this application and delivered to your browser when you use related features. The chess engines among them each run as a separate Web Worker process and communicate with the application only through the standard text-based UCI protocol.
Stockfish
A strong open source UCI chess engine, used here as the default AI opponent.
- Source code:
- https://github.com/official-stockfish/Stockfish
- License:
- GNU General Public License v3.0
Lc0 (Leela Chess Zero)
A neural network chess engine, used here to run Maia weights for human-like AI opponents.
- Source code:
- https://github.com/LeelaChessZero/lc0
- License:
- GNU General Public License v3.0
Maia Chess (neural network weights)
Neural network weights that model human chess play at specific rating levels, developed by the Computational Social Science Lab at the University of Toronto.
- Source code:
- https://github.com/CSSLab/maia-chess
- License:
- GNU General Public License v3.0
libheif (via heic-to)
An HEIF/HEIC image decoder compiled to WebAssembly. It runs in your browser to convert HEIC photos (the iPhone default format) to JPEG before they are uploaded. Bundled through the heic-to library.
- Source code:
- https://github.com/strukturag/libheif
- License:
- GNU Lesser General Public License v3.0
GPL v3 Compliance
The components above are licensed under the GNU General Public License version 3 (GPL v3) and are bundled here without modification. The corresponding source code is publicly available at the upstream repositories linked above.
libheif is additionally provided under the GNU Lesser General Public License version 3 (LGPL v3), which applies the terms of the GPL v3 with additional permissions. It is bundled without modification, and its source code is available at the upstream repository linked above.
View the full GPL v3 license text / Also available at the GNU Project website
Last Updated: May 13, 2026