Licences and source code
Explain My Chess is built on open-source software and open data. This page lists each part, its licence and where to get the source.
Components
| Component | Licence | Source |
|---|---|---|
| Stockfish 18.0.8 (WebAssembly build by nmrugg/stockfish.js) | GPL-3.0 | github.com/nmrugg/stockfish.js |
| chess.js | BSD-2-Clause | github.com/jhlywa/chess.js |
| cm-chessboard | MIT | github.com/shaack/cm-chessboard |
| Chessnut piece set by Alexis Luengas | Apache-2.0 | github.com/LexLuengas/chessnut-pieces |
| Opening names (lichess-org/chess-openings) | CC0-1.0 | github.com/lichess-org/chess-openings |
| Fonts: Newsreader, Instrument Sans, JetBrains Mono (self-hosted via Fontsource) | SIL Open Font License 1.1 | openfontlicense.org |
| Icons: Lucide | ISC | lucide.dev |
The Chessnut licence file is also served at /pieces/LICENSE.md.
Stockfish
The analysis engine is Stockfish 18.0.8, in the WebAssembly build by nmrugg/stockfish.js. It is licensed under the GNU General Public License v3.0.
The engine runs in your browser as a separate, unmodified Web Worker file. The rest of the site talks to it only through messages in the UCI protocol. None of our own code includes engine source.
- Upstream engine: github.com/official-stockfish/Stockfish
- WebAssembly build, exact source (tag v18.0.8): github.com/nmrugg/stockfish.js, commit 93c9945
- Our own copy of the complete corresponding source, with build script and network file: /engine/source/stockfish.js-18.0.8-src.tar.gz (SHA-256
c5540cdf2e68985b17f3289e993299144e7025f7632d71439006d8ce643f2f2e) - Build notes and checksums are listed in /engine/SOURCE.md.
The engine files are served unchanged from the /engine/ folder of this site, so you can download exactly what your browser runs.
Example game
The example review uses the Opera Game: Paul Morphy vs Duke Karl of Brunswick and Count Isouard, Paris 1858. The game is in the public domain.