@lichess-org/stockfish-web

WebAssembly builds for Stockfish.

This package is optimized for the lichess.org website, which needs multiple builds and chess variants. It is not straight-forward to load and use.

Check out https://github.com/nmrugg/stockfish.js for a simpler browser Stockfish.

Building

./build.py downloads sources to the ./fishes folder, applies diffs from the ./patches folder, and builds targets using local emsdk with a matching version, podman or docker.

# Example: Clean and make all targets with pgo and final bench signature verification
./build.py clean all --pgo --verify-bench

# Example: Clean and make dist targets for web with a preallocated pthread pool size of 8
./build.py --ld-flags='-sENVIRONMENT=web,worker -sPTHREAD_POOL_SIZE=8' clean dist

Use --cxx-flags to override the default emcc flags (-O3 -DNDEBUG --closure=1).

Use --ld-flags to override default linker flags (--ld-flags='-sENVIRONMENT=web,worker,node').

Check ./build.py --help for all available targets.

Edit the Stockfish sources within ./fishes. Contribute your edits via patch file:

# Example: Update `sf_19.patch` with your commits
cd fishes/sf_19
git format-patch stockfish-web/base --stdout > ../../patches/sf_19.patch

Run locally on node

./tools/wasm-cli.ts bootstraps the emscripten module and also automatically downloads the required nnue files into the current working directory.

./build.py
node ./tools/wasm-cli.ts ./sf_19.js
uci

Sources

sf_19_smallnet (Stockfish 19 with sscg13/size-optimize-nnue)

• repo: https://github.com/official-stockfish/Stockfish
• base: edb0d9db
• tag: sf_19 (patches include rebase of sscg13/size-optimize-nnue)
• nnue: nn-61e7af4bb97d.nnue

sf_19 (Stockfish 19)

• repo: https://github.com/official-stockfish/Stockfish
• base: edb0d9db
• tag: sf_19
• nnue: nn-1a298aa575a0.nnue

fsf_14 (Fairy-Stockfish 14)

• repo: https://github.com/fairy-stockfish/Fairy-Stockfish
• base: a621470b
• nnues: see repo links

Older repositories kept for compatibility

stockfish-nnue.wasm

Stockfish 14 without dynamic import() in WebWorker.

stockfish.wasm and stockfish-mv.wasm

SF_classical (strongest handcoded eval) and multi-variant equivalent. No SIMD. No dynamic import() in WebWorker.

stockfish.js

Stockfish 10 in pure JavaScript or WebAssembly without shared memory.