lichess-org/stockfish.js

stockfish.js

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

[!IMPORTANT] Maintained with bugfixes to keep supporting older browsers, but active development is happening on https://github.com/lichess-org/stockfish-web

Releases

About 1.4MB uncompressed, 250 KB gzipped.

Building

Install Emscripten and uglifyjs, then:

./build.sh

Or using Docker:

docker run --user $(id -u):$(id -g) --volume $(pwd):/home/builder/stockfish.js:rw niklasf/emscripten-for-stockfish

Usage

var wasmSupported = typeof WebAssembly === 'object' && WebAssembly.validate(Uint8Array.of(0x0, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00));

var stockfish = new Worker(wasmSupported ? 'stockfish.wasm.js' : '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.