Licences & corresponding source
Everything this site runs on in your browser is open-source software. The chess engine is distributed unmodified; its corresponding source is available from the upstream repositories linked below.
Stockfish
- Licence
- GNU General Public License, version 3 — full text
- Copyright
- The Stockfish developers (see AUTHORS)
- Distributed files
stockfish-18-lite.js/.wasmandstockfish-18-lite-single.js/.wasm— the lite builds from the npm packagestockfish18.0.5, unmodified. The small NNUE evaluation network is embedded in the WASM binary.- Corresponding source
- nmrugg/stockfish.js (the WebAssembly build) · official-stockfish/Stockfish (upstream engine)
Stockfish is used only for hints, analysis and play against the engine. Whether your solution is correct is decided by the composer's published solution, not by the engine.
Chess piece images
- Asset
- The standard SVG chess pieces, as shipped with react-chessboard
- Author
- Colin M.L. Burnett (Cburnett)
- Licence
- Creative Commons Attribution-ShareAlike 3.0 Unported
- Source
- Wikimedia Commons · used as-is
chess.js
- Version
- 1.4.0
- Licence
- BSD 2-Clause License
- Copyright
- © 2025, Jeff Hlywa
- Source
- jhlywa/chess.js (licence text in the repository)
react-chessboard
- Version
- 4.7.3
- Licence
- MIT License
- Copyright
- © 2022 Ryan Gregory
- Source
- Clariity/react-chessboard
React
- Version
- 19.2
- Licence
- MIT License
- Copyright
- © Meta Platforms, Inc. and affiliates
- Source
- facebook/react
Tailwind CSS
- Version
- 4.2
- Licence
- MIT License
- Copyright
- © Tailwind Labs, Inc.
- Source
- tailwindlabs/tailwindcss
Fonts
Baloo 2, Inter and IBM Plex Mono are served by Google Fonts under the SIL Open Font License 1.1. They are not redistributed by this site.
Problem data
Positions, stipulations, solutions and bibliographic data come from YACPDB. The problems themselves are the work of their composers, who are named on every problem page once it has been solved.
This site's own code
The site's own code is © 2026 Ushiyutvj, all rights reserved. It is not covered by any of the licences above. The source can be read on GitHub for reference; copying it or using it in another site or product needs the author's permission.