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Credits and Licences

Chess Mirror includes open-source software written by others. The same list, with the licence texts, is in the app under Licences and source code.

Stockfish: GNU General Public License v3 (GPL-3.0)

• Stockfish.js 19, © 2026 Chess.com, LLC, a WebAssembly build of Stockfish. Source: https://github.com/nmrugg/stockfish.js (release v19.0.0).
• Stockfish by T. Romstad, M. Costalba, J. Kiiski, G. Linscott and other contributors. Source: https://github.com/official-stockfish/Stockfish. Neural network by Chris Bao (sscg13).
• Our change: in the engine's loader, one function was changed so the engine starts from data embedded in the page instead of downloading a separate file. Nothing else in the engine was altered.
• You may copy, study, change and share this engine under the GPL-3.0. You can get the complete corresponding source code at the addresses above. [⚖ confirm the exact source and written-offer wording you must give, and how it applies to the single-file app you distribute.]

chess.js 0.10.3: BSD 2-Clause

Copyright (c) 2020, Jeff Hlywa. Built into the page. The licence text is shown in the app and kept in the file's header.

IBM Plex Sans and IBM Plex Sans Condensed: SIL Open Font License 1.1

Copyright © IBM Corp. Built into the page. The licence text is shown in the app.

Chess piece artwork: "cburnett" set

By Colin M.L. Burnett, available under free licences (GPL, BSD and GFDL) [⚖ choose and state the licence you rely on].

Loaded only if you choose to pay

Paddle.js, loaded from Paddle's own server only when you press "Go Pro". It is not part of this page and is under Paddle's terms.

Names

chess.com, Lichess, Stockfish, IBM, Paddle and Supabase are names of their owners. Chess Mirror is not affiliated with or endorsed by them.