TheoryChess uses the following open-source work, with thanks to everyone behind it. Each is subject to its own licence.
Stockfish.js
Moves are evaluated by the WebAssembly build of the Stockfish chess engine, running in your browser.
- Version: Stockfish.js 19.0.0 (npm package
[email protected]). The engine files served by the site are copied from this version unmodified. - Source code: github.com/nmrugg/stockfish.js (v19.0.0) and the package source archive stockfish-19.0.0.tgz. Stockfish: stockfishchess.org
- Licence: GNU GPL v3. The licence text is published next to the engine files at /engine/Copying.txt. If you cannot reach the source through the links above, write to [email protected] and we will send it to you.
Opening data
- Source: lichess-org/chess-openings
- Licence: CC0 1.0 (public domain)
Chess pieces (cburnett)
- Design: Colin M.L. Burnett
- Source: lichess-org/lila
- Licence: GNU GPL v2 or later. Used unmodified.
3D chess piece model
- “A Beautiful Game” © 2020 ASWF (Academy Software Foundation), MaterialX Project, originally made by Moeen Sayed and Mujtaba Sayed. glTF conversion © 2022 Ed Mackey.
- Source: Khronos glTF Sample Assets
- Licence: CC BY 4.0
- Changes: one model per piece type was kept; the board, materials and textures were removed; the models were centred, scaled and simplified.
Typeface
- Plus Jakarta Sans, Tokotype. Licence: SIL Open Font License 1.1
Other open-source software
The site is built with open-source libraries such as Next.js, React, NestJS, Prisma, Better Auth, chess.js and Tailwind CSS, distributed under MIT, Apache 2.0 and similar permissive licences. Each library’s licence text ships with its package.