Credits & licenses
The chess artwork and engine are served locally with their original license notices.
Chessnut pieces
Copyright 2015 Alexis Luengas. The twelve SVG chess pieces are redistributed unmodified under the Apache License 2.0.
Stockfish 19
Stockfish by Tord Romstad, Marco Costalba, Joona Kiiski, Gary Linscott, and contributors. Stockfish.js WebAssembly port by Nathan Rugg / Chess.com, LLC and contributors. Neural network by Chris Bao (sscg13).
This site distributes the unmodified lite single-thread engine from Stockfish.js 19.0.1 under GNU GPL v3. It runs in a separate browser worker.
Original release · GPL v3 license · Authors
Download the corresponding source code and build scripts and the exact lite neural network. Extract the source, put the network in src/, install its build dependencies and Emscripten 6.0.9, and run node build.js --lite --single-threaded --no-split. The source archive includes the complete upstream build instructions.
Supporting libraries
chess.js 1.4.0 by Jeff Hlywa and contributors — BSD-2-Clause license.
ws 8.22.1 by Einar Otto Stangvik, Arnout Kazemier, Luigi Pinca, and contributors — MIT license.
Original visuals
Board themes, layout, and diagrams are rendered with original CSS and the credited piece set. No third-party photos or board textures are used.