RandomX bonanza

In-browser Monero (RandomX) miner achieving up to ~24% of native execution efficiency, packaged with an easy to set up demo environment. The raw miner payload is sub 500 KB. Shoutout to Opus 4.7, Opus 5.5 and l1mey112's semifloat implementation.

Requirements

• emcc (Emscripten SDK) ≥ 3.1
• clang
• binaryen (wasm-opt)
• node ≥ 18

brew install emscripten node binaryen llvm           # macOS
sudo apt install emscripten nodejs clang binaryen    # Debian/Ubuntu
sudo dnf install emscripten nodejs clang binaryen    # Fedora
sudo pacman -S  emscripten nodejs clang binaryen     # Arch

If your distro's emscripten is too old, install the upstream SDK instead:

git clone https://github.com/emscripten-core/emsdk
cd emsdk && ./emsdk install latest && ./emsdk activate latest
source ./emsdk_env.sh

Toolchain check (ws is vendored under vendor/, no npm install):

make install

Build & run

make build       # → public/randomx{,_st}.{js,wasm}
make serve       # build + start the proxy on http://localhost:8080
make test        # canonical RandomX hash vs. reference test vector
make embed       # build + package the jsDelivr embed into dist/
make test-embed  # embed lifecycle and consent tests
make bench       # full-mode hashrate sweep (see Bench)
make bench-light # light-mode hashrate sweep (see Bench)
make clean       # remove build outputs
make fclean      # clean + drop .make/ stamps
make re          # fclean + build

Browser support

Firefox is mostly untested.

• Chromium / Firefox — work out of the box over plain HTTP on localhost, since browsers treat localhost as a secure context (the proxy still sends the COOP/COEP headers SharedArrayBuffer / wasm pthreads need). Served without those headers, the miner falls back to single-thread light-mode workers (see ?sab=0).
• Safari — refuses SharedArrayBuffer outside HTTPS even on localhost, so the local demo won't run there as shipped. Put an HTTPS proxy in front (e.g. caddy reverse-proxy --to :8080) and Safari works fine — the live preview at https://randomx.cc/ runs without issues.

Bench

make bench                           # regfile micro-bench + sweep 1,4,10,32 threads @ 30 s/pass
make bench DURATION=10               # shorter pass
make bench SWEEP=1,8,16,32           # custom thread set
make bench INIT_THREADS=16           # dataset init parallelism (1–32)
make bench SWEEP=32 DURATION=60      # single 32-thread, 60 s pass
make bench PROFILE=arm               # JIT generator profile: auto | arm | x86
make bench-light                     # light-mode sweep (no SharedArrayBuffer), fixed passes

Efficiency

Apple M4 base · 10 cores · make bench (30 s/pass) vs. native xmrig --bench=250K (fast mode) at the same thread count. The xmrig numbers come from xmrig's master branch, chosen deliberately over the better performing dev, to make the number look more interesting.

threads	init	WASM H/s	xmrig H/s	efficiency
1	4.69 s	175	696*	25.1 %
4	4.76 s	647	2673*	24.2 %
10	4.74 s	947	4081*	23.2 %
32	4.69 s	993	3904*	25.4 %

_{* credit where it's due, the dev branch of xmrig performs at least 10% better than the numbers listed}

In the browser on the same machine (32 threads): Chrome ~850–880 H/s, Safari ~800 H/s, Firefox ~700 H/s.

Light mode, make bench-light vs. xmrig --bench=250K --randomx-mode=light (xmrig threads share one cache; the light workers each build their own):

threads	init	WASM H/s	xmrig H/s	efficiency
1	0.49 s	47	70	66.6 %
4	0.56 s	165	254	64.9 %
10	0.88 s	291	546	53.3 %
32	10.90 s	289	533	54.2 %

With full-dataset workers (NF+M = N full-dataset + M light workers):

workers	init	WASM H/s	RAM (est.)
1F	35.20 s	170	~2.5 GiB
1F+3	11.06 s	293	~3.4 GiB
1F+9	6.95 s	360	~5.2 GiB
2F	19.13 s	337	~5.1 GiB
2F+2	11.75 s	417	~5.7 GiB
2F+8	7.02 s	427	~7.4 GiB

This approach is relevant since it doesn't require SharedArrayBuffer.

Payload

Demo page: 433 KB per load.

index.html       33.2 KB     ui shell
miner.js         41.9 KB     ws client + ui control
worker.js        37.6 KB     wasm engine driver
randomx.js       57.8 KB     emscripten glue
randomx.wasm    262.9 KB     randomx engine + JIT + supjit kernel

Embed: 428 KB in full mode, 396 KB in light mode.

embed.js            68.6 KB     loader + widget + API
embed-worker.js      1.1 KB     full-mode thread broker
worker.js           37.6 KB     wasm engine driver
randomx.js          57.8 KB     emscripten glue (full)
randomx.wasm       262.9 KB     randomx engine (full)
randomx_st.js       42.1 KB     emscripten glue (light)
randomx_st.wasm    247.9 KB     randomx engine (light)
fb_full.js          11.8 KB     full-dataset replicas (light, only when replicas are on)

Configuration

See the Documentation of the elegant control plane of our embed script.

Layout

Makefile            install / build / serve / bench / test / embed / clean
config.js           wallet + pool + port defaults
proxy/index.js      HTTP + WS + raw-TCP stratum bridge
public/             browser assets (miner.js, worker.js, embed.js, built randomx{,_st}.{js,wasm})
dist/               jsDelivr/npm-ready embed distribution
scripts/            package-embed.mjs
tests/              embed tests
bench/              bench_webui.mjs · bench_sweep.mjs · bench_regfile.mjs · canonical_hash.mjs · …
docs/               embed script documentation
readme/             README images
wasm/               vendored RandomX C/C++ sources + build.sh
vendor/ws/          vendored npm ws (no npm install required)