Licenses & Credits

Last updated: 24 June 2026

Chess Blues is built with open-source software and uses data from several third parties. We are grateful to their authors and communities. Chess Blues is independent and is not affiliated with, endorsed by, or sponsored by Chess.com or Lichess.

Stockfish chess engine

Move analysis and game review are powered by Stockfish, a free and open-source chess engine, used both in your browser (WebAssembly build) and on our server.

Stockfish is licensed under the GNU General Public License, version 3 (GPL-3.0). In accordance with that license, the complete corresponding source code for the version of Stockfish we distribute is available from the official repository at github.com/official-stockfish/Stockfish. Stockfish is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GPL-3.0 for details.

Third-party data sources

  • Lichess — opening explorer and cloud evaluation data, and game import, via the Lichess API. Lichess is a registered trademark of the Lichess non-profit. Lichess puzzle data is released under Creative Commons CC0.
  • Chess.com — game import via the public Chess.com Published Data API. "Chess.com" is a trademark of Chess.com, LLC, used here only to describe interoperability.
  • OpenAI — AI coaching text, transcription, and voice narration via the OpenAI API.

Software libraries

This product includes open-source libraries (including Next.js, React, FastAPI, python-chess, and others) under permissive licenses such as MIT, Apache-2.0, and BSD. A full list is available in our package manifests.

Artwork

Move-classification badges and decorative chess artwork used in Chess Blues are original to Chess Blues. The on-board chess piece set is provided by the open-source board component we use, under its own license.