bitcoin-kernel / node

A browser-native Bitcoin node. Validate Bitcoin's consensus rules in a tab, persist the chain to OPFS, and sync through a thin local bridge. Built on the bitcoin-kernel engine.

Status: early. The Tier 0 core runs in Node today (testnet4). See the roadmap.

Try it now (Node)

npm install
npm test                      # deterministic testnet4 consensus checks
npm run bench                 # header-validation throughput
node src/sync-testnet4.js     # live: sync + fully validate the testnet4 header chain

sync-testnet4.js connects to a real testnet4 peer over TCP, syncs the header chain, fully validates it incrementally (proof of work, difficulty, the BIP 94 timewarp fix, the 20-minute min-difficulty walk-back), handles reorgs by the most-work rule, persists it, resumes from disk on the next run, and cross-checks the tip against other p2p peers (never a third-party explorer). Recent run: 140k headers, all validated, persisted; a resume completed in 0.3s. Header validation measures ~15-21k headers/sec on the pure-JS engine.

Headless and browser-ready by design

The platform-specific pieces are interfaces, so the core logic is pure and proven headless before it ever touches a browser:

• src/store/header-store.js — the HeaderStore interface with MemoryHeaderStore (tests) and FileHeaderStore (Node). The browser adds OpfsHeaderStore with the same logic over an OPFS sync access handle.
• src/chain/header-sync.js — HeaderSync, a platform-agnostic engine that resumes, validates each header, and reorgs by most-work. It depends only on the store interface, the engine, and a transport-agnostic fetchHeaders(locator).

So the browser node is two swaps: FileHeaderStore → OpfsHeaderStore, and the TCP Peer → a WS-bridge Peer. Everything else is the same code, covered by headless unit tests (npm test).

The idea: usable first, trustless later

Three resource tiers. Opt into more to trust less.

Tier	Does	Cost	Device
0 Lite	headers + Neutrino wallet (BIP 157/158)	~100 MB, minutes	phone
1 Validating	assumeutxo snapshot, validate new blocks live	a few GB	laptop
2 Full	backfill genesis to tip, fully trustless	~650 GB, lots of RAM	desktop

Pillars

• Storage: OPFS (synchronous access handles in a Web Worker). In Node, a flat file stands in.
• Compute: WASM-SIMD secp256k1 + Web Workers; the UTXO set lives in RAM, not a DB.
• Networking: a small local WebSocket-to-TCP bridge (a browser cannot open raw TCP).

Everything is built for both mainnet and testnet4 by passing the network; testnet4 is the default first target because it is small and exercises the trickiest difficulty rules. Every milestone is gated by a benchmark.

Independent community project, not affiliated with Bitcoin Core.