Engine source & licenses

This app uses open-source components with their own licenses. The engine for standard chess runs locally in a dedicated browser Worker. Native Archer opponents, when connected, run on a separately secured server.

Stockfish 18 Lite

Stockfish is developed by the Stockfish contributors. This app distributes Nathan Rugg’s Stockfish.js port, package 18.0.8, in its unmodified Lite single-thread build. Lite is smaller and weaker than full Stockfish 18. The engine is licensed under GNU GPL version 3, without warranty.

Corresponding source and the exact neural-network weights are available here, alongside the binary:

• Stockfish.js source archive · commit 93c994592dcf3b4b21052ab925e9b534df9c0918
• Lite network · nn-9067e33176e8.nnue
• Build instructions, provenance and SHA-256 checksums
• Stockfish.js upstream · Stockfish 18 release

Board and rules

Native Archer play uses our modified Stockfish search with either original frozen networks or the selected fallback200 fine-tuned networks. It is not unmodified Stockfish, and the fine-tuned name is not a strength claim. The exact binary/network identities and search settings are included in each native game export. Native binaries and model files are not downloaded by this website.

• chess.js 1.4.0, Jeff Hlywa: BSD 2-Clause. Used for standard chess rules.
• react-chessboard 5.12.1, Ryan Gregory and contributors: MIT. Used for the interactive board.
• The standard chess piece artwork by Cburnett / Wikimedia Commons is used through react-chessboard, without artwork modifications, under Creative Commons Attribution-ShareAlike 3.0. The board library’s MIT license does not replace the artwork license.
• Archer and interface icons: Lucide, ISC license. The archer combines the BowArrow and ArrowUp interface icons.

Third-party dependency notices cover the installed runtime and development packages. Preserve applicable notices and engine source downloads when redistributing or hosting this app. Deployment at EY requires its own legal and security review.

Privacy in this first release

Your browser receives an HTTP-only private-session cookie. Games, actions, results and dice outcomes are saved on the server and visible only to the two seats’ sessions. Invitations are one-use bearer links. There are no public profiles, chat, analytics or password accounts. Clearing site cookies loses access; export important records before doing so.

This is an untimed experimental ruleset, not a rated competition platform. It does not detect outside engine assistance, certify randomness to a distrustful opponent, or implement an exhaustive solver for every possible dead position.