Licenses and credits
Chess411 is built on open source software and artwork. This page lists what the site ships, who made it, and the terms it comes under.
Stockfish
Every analysis feature on Chess411 runs on Stockfish, the strongest open source chess engine. Stockfish is copyright T. Romstad, M. Costalba, J. Kiiski, G. Linscott and other contributors, and is free software licensed under the GNU General Public License, version 3.
The next move calculator runs Stockfish 18 directly in your browser using Stockfish.js, the WebAssembly build of Stockfish, copyright Chess.com, LLC, also released under the GPL v3, with NNUE evaluation networks by Linmiao Xu. Game review runs Stockfish 18 natively on our own servers.
The complete source code for the engine is available at github.com/official-stockfish/Stockfish, and the source for the exact browser build we ship is available at github.com/nmrugg/stockfish.js. A copy of the license ships with this site at /stockfish/gpl-3.0.txt.
Chess piece sets
The piece images on our boards are the work of their original authors and are redistributed under their original licenses. The Settings dialog names the author and license of whichever set you have selected, and the full table of credits ships with the site at /pieces/LICENSES.txt.
Board scanning
The position scanner reads screenshots and photos in your browser using ONNX Runtime Web, copyright Microsoft Corporation, released under the MIT license.