stockfish.wasm
WebAssembly port of the strong chess engine
Stockfish. See it in action
on https://lichess.org/analysis.
Superceded by Stockfish with NNUE
This port is branched from SF_classical
.
See https://github.com/hi-ogawa/Stockfish for a WebAssembly port with NNUE support.
Requirements
Uses the latest WebAssembly threading proposal. Requires these HTTP headers
on the top level response:
Cross-Origin-Embedder-Policy: require-corp
Cross-Origin-Opener-Policy: same-origin
And the following header on the included files:
Cross-Origin-Embedder-Policy: require-corp
Chromium based (desktop only)
- Since Chromium 79: Full support.
- Chromium 74: Supports treading, but cannot allocate additional memory.
The default allocation suffices for up to 2 threads and 16 MB hash.
- Chromium 70 to 73: Needs flag
chrome://flags/#enable-webassembly-threads
or
Origin Trial.
Firefox
- Since Firefox 79: Full support.
- Firefox 72 to 78: Structured cloning can no longer be enabled with flags, except on nightlies.
- Firefox 71: Requires
javascript.options.shared_memory
and dom.postMessage.sharedArrayBuffer.withCOOP_COEP
to be enabled in about:flags
. - Firefox 68 to 70: Requires
javascript.options.shared_memory
to be enabled in about:flags
Other browsers
No support.
See stockfish.js for a more
portable but single-threaded version.
Feature detection
function wasmThreadsSupported() {
const source = Uint8Array.of(0x0, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00);
if (
typeof WebAssembly !== "object" ||
typeof WebAssembly.validate !== "function"
)
return false;
if (!WebAssembly.validate(source)) return false;
if (typeof SharedArrayBuffer !== "function") return false;
if (typeof Atomics !== "object") return false;
const mem = new WebAssembly.Memory({ shared: true, initial: 8, maximum: 16 });
if (!(mem.buffer instanceof SharedArrayBuffer)) return false;
try {
window.postMessage(mem, "*");
} catch (e) {
return false;
}
try {
mem.grow(8);
} catch (e) {
return false;
}
return true;
}
Current limitations
- Hashtable: 1024 MB. You may want to check
navigator.deviceMemory
before allocating. - Threads: 32. You may want to check
navigator.hardwareConcurrency
.
May be capped lower (e.g., dom.workers.maxPerDomain
in Firefox). - Can hang when UCI protocol is misused. (Do not send invalid commands or
positions. While the engine is searching, do not change options or start
additional searches).
- No NNUE support.
- No Syzygy tablebase support.
Building
Assuming em++ (^2.0.13
) is available:
npm run-script prepare
Usage
Requires stockfish.js
, stockfish.wasm
and stockfish.worker.js
(total size ~400K, ~150K gzipped) to be served from the same directory.
<script src="stockfish.js"></script>
<script>
Stockfish().then((sf) => {
sf.addMessageListener((line) => {
console.log(line);
});
sf.postMessage("uci");
});
</script>
Or from recent node (v14.4.0 tested) with flags
--experimental-wasm-threads --experimental-wasm-bulk-memory
:
const Stockfish = require("stockfish.wasm");
Stockfish().then((sf) => {
});
License
Thanks to the Stockfish team for sharing the engine under the GPL3.