Credits and licenses

Bots, hints, the evaluation bar and game review are powered by Stockfish.js (Stockfish 19, “lite single-threaded” build, WebAssembly), a port of the Stockfish engine. It runs entirely in your browser, in a separate Web Worker.

Stockfish and Stockfish.js are distributed under the GNU General Public License v3 (GPL-3.0). Source code of the build used here: github.com/nmrugg/stockfish.js (version 19.0.1, npm package stockfish). License text: COPYING.txt · gnu.org/licenses/gpl-3.0.

Engine files your browser downloads: stockfish-19-lite-single.js, ⤓stockfish-19-lite-single.wasm (download, 1.8 MB).

The 3D board assets come from Poly Haven and are published under CC0 1.0 (public domain). Attribution is not required — we give it as a thank-you.

• 3D pieces “Chess Set” polyhaven.com/a/chess_set
• HDRI lighting “Studio Small 09” polyhaven.com/a/studio_small_09
• Wood texture “Wood Table 001” polyhaven.com/a/wood_table_001

Changes

• Pieces — from the 2k glTF version: the board and duplicate pieces removed (one model per type and color), models centered and scaled (1 unit = 1 square), compressed with meshopt; textures downscaled to 1024 px and re-encoded as WebP.
• HDRI — an unmodified copy of studio_small_09_1k.hdr.
• Wood — 1k maps (diff, nor_gl, arm, rough) re-encoded as WebP.

Libraries

• chess.js BSD-2-Clause
• cm-chessboard MIT
• three.js MIT
• Threlte MIT