stockfish.js

The strong open source chess engine Stockfish compiled to JavaScript using Emscripten. See it in action for local computer analysis on lichess.org.

Downloads

About 1MB uncompressed, 220 KB gzipped:

• stockfish.js based on original Stockfish
• stockfish.js with multi-variant support by @ddugovic

Building

Install Emscripten, then:

cd src
make ARCH=js build

Usage

var stockfish = new Worker('stockfish.js');

stockfish.addEventListener('message', function (e) {
  console.log(e.data);
});

stockfish.postMessage('uci');

Changes to original Stockfish

• Expose as web worker.
• Web workers are inherently single threaded. Limit to one thread.
• Break down main iterative deepening loop to allow interrupting search.
• Limit total memory to 32 MB.
• Disable Syzygy tablebases.
• Disable benchmark.

Acknowledgements

Thanks to @nmrugg for doing the same thing with Stockfish 6, to @ddugovic for his multi-variant Stockfish fork and to the Stockfish team for ... Stockfish.