RandomX bonanza

In-browser Monero (RandomX) miner achieving ~13% of native execution efficiency, packaged with an easy to setup demo environment including a simple proxy with live pool presets. The raw miner payload is sub 600 KB. Shoutout to Opus 4.7 and l1mey112's semifloat implementation.

Requirements

• emcc (Emscripten SDK) ≥ 3.1
• clang
• binaryen (wasm-opt)
• node ≥ 16

Common package-manager examples:

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

Install project dependencies (toolchain check only — ws is vendored under vendor/, no npm install):

make install

Build & run

make build      # → public/randomx.{js,wasm}
make serve      # build + start the proxy on http://localhost:8080
make test       # canonical RandomX hash vs. reference test vector
make clean      # remove build outputs
make fclean     # clean + drop .make/ stamps
make re         # fclean + build

Open http://localhost:8080, press Start. The Wallet setup panel overrides wallet/pool per session (persisted in localStorage).

Browser support

• 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).
• Safari — refuses SharedArrayBuffer outside HTTPS even on localhost, so the local demo won't run there as shipped. Drop a self-signed cert in front of the proxy (e.g. caddy reverse-proxy --to :8080 or any HTTPS fronting of your choice) and Safari works fine — the live preview at https://randomx.cc/ runs in Safari without issues.

Bench

make bench                           # sweep 1,4,32 mining 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

Mirrors the webui worker exactly: threaded-interpreter JIT (+ INLINE_FPRC_ZERO

• V3 regs_in_memory + split_inner_dispatch + supjit kernel) and async dataset init (rxInitDatasetStart / rxInitDatasetProgress / rxInitDatasetJoin). Each pass forks a fresh node process so JIT/pthread state cannot leak between thread counts. CPU model + core count are detected and printed in the summary.

The standalone scripts also work directly:

node bench/bench_webui.mjs --threads 32 --duration 30
node bench/bench_sweep.mjs --sweep 1,4,32 --duration 30
node bench/bench_regfile.mjs                   # JIT codegen micro-bench

Efficiency

Apple M4 base · 10 cores · make bench (30 s/pass) vs. native xmrig --bench=1M at the same thread count:

threads   init     WASM H/s    xmrig H/s    efficiency
─────────────────────────────────────────────────────
   1     7.54 s        90          693         13.0 %
   4     6.95 s       362         2676         13.5 %
  32     6.65 s       586       ~4000 ¹       14.7 %

WASM tracks ~13 % of native per thread and ~15 % at full load.

Payload

Total served to the browser per page load: 577 KB.

index.html       15.1 KB     ui shell
miner.js         35.9 KB     ws client + ui control
worker.js        27.2 KB     wasm engine driver
randomx.js       47.1 KB     emscripten glue
randomx.wasm    451.7 KB     randomx engine + JIT + supjit kernel

Native miners

The proxy exposes a raw TCP stratum endpoint alongside the WebSocket one, so any standard stratum client (xmrig, p2pool, …) can join the same upstream session as the browser tab:

xmrig -o 127.0.0.1:8081 -u <monero-address> -p worker --tls=false

Configuration

config.js:

WALLET            Monero address mined to
POOL_HOST/PORT    upstream pool
WORKER_NAME       stratum worker tag
WS_PORT           HTTP + WebSocket port  (default 8080)
STRATUM_TCP_PORT  raw TCP stratum port   (default 8081)

The Wallet setup panel in the UI overrides these per-session without a restart.

URL parameters:

• ?light=1 — light mode (256 MiB, instant start, low hashrate)
• ?nojit=1 — disable the C-side JIT
• ?threads=N — start with N mining threads (1–32)
• ?init_threads=N — dataset-init parallelism (default 32)
• ?profile=1 — per-phase wall-clock profiling in the worker

Layout

Makefile            install / build / serve / bench / test / clean
config.js           wallet + pool + port defaults
proxy/index.js      HTTP + WS + raw-TCP stratum bridge
public/             browser assets (miner.js, worker.js, built randomx.{js,wasm})
bench/              bench_webui.mjs · bench_sweep.mjs · bench_regfile.mjs · canonical_hash.mjs
wasm/               vendored RandomX C/C++ sources + build.sh
vendor/ws/          vendored npm ws (no npm install required)