blake3-wasm-rs

blake3-wasm-rs is a WebAssembly port of the BLAKE3 cryptographic hash function written in Rust. It enables fast and secure hashing right inside browsers and Node.js.

build

# lets build it!

# For NodeJS
wasm-pack build --target nodejs --release

# For the web!
wasm-pack build --target web --release

SIMD is enabled via wasm32_simd feature in Cargo.toml and requires:

# .cargo/config.toml
[target.wasm32-unknown-unknown]
rustflags = ["-C", "target-feature=+simd128"]

Usage

import * as blake3 from 'blake3-wasm-rs';

const data = new TextEncoder().encode('hello world');
const key = new Uint8Array(32).fill(1);

// One-shot hashing
blake3.hash(data);
blake3.hashXof(data, 64);        // variable output length
blake3.keyedHash(data, key);     // key must be exactly 32 bytes
blake3.deriveKey('my context', key);

// Conctruct for Streaming
{
    using h = new blake3.Hasher();
    h.update(data.slice(0, 5));
    h.update(data.slice(5));
    h.finalize();
    h.finalizeXof(64);
    h.reset();
}

// Streaming
// Keyed (MAC mode)
{
    using mac = blake3.Hasher.newKeyed(key);
    mac.update(data);
    mac.finalize();
}

// Streaming
// Key derivation mode
{
    using kdf = blake3.Hasher.newDeriveKey('my app v1 :: subkey');
    kdf.update(key);
    kdf.finalize();
}

// Batch hashing without re-allocating
{
    using h = new blake3.Hasher();
    h.update(chunk1);
    const first = h.finalizeAndReset();
    h.update(chunk2);
    const second = h.finalizeAndReset();
}

Named imports

import { hash, hashXof, keyedHash, deriveKey, Hasher } from 'blake3-wasm-rs';

const data = new TextEncoder().encode('hello world');
const key = new Uint8Array(32).fill(1);

// One-shot hashing
hash(data);
hashXof(data, 64);          // variable output length
keyedHash(data, key);       // key must be exactly 32 bytes
deriveKey('my context', key);

// Streaming
{
    using h = new Hasher();
    h.update(data.slice(0, 5));
    h.update(data.slice(5));
    h.finalize();
    h.finalizeXof(64);
    h.reset();
}

// Keyed (MAC mode)
{
    using mac = Hasher.newKeyed(key);
    mac.update(data);
    mac.finalize();
}

// Key derivation mode
{
    using kdf = Hasher.newDeriveKey('my app v1 :: subkey');
    kdf.update(key);
    kdf.finalize();
}

// Batch hashing without re-allocating
{
    using h = new Hasher();
    h.update(chunk1);
    const first = h.finalizeAndReset();
    h.update(chunk2);
    const second = h.finalizeAndReset();
}

API

Functions

Function	Returns	Description
hash(data)	Uint8Array	One-shot 32-byte BLAKE3 digest
hashXof(data, outLen)	Uint8Array	Variable-length digest (XOF mode)
keyedHash(data, key)	Uint8Array	Keyed hash / MAC (key must be exactly 32 bytes)
deriveKey(context, keyMaterial)	Uint8Array	Derive a 32-byte subkey

Hasher class

Method	Returns	Description
new Hasher()	Hasher	Streaming hasher, unkeyed
Hasher.newKeyed(key)	Hasher	Streaming hasher, MAC mode (key must be exactly 32 bytes)
Hasher.newDeriveKey(context)	Hasher	Streaming hasher, KDF mode
.update(data)	void	Feed data, can be called multiple times
.finalize()	Uint8Array	32-byte digest, non-destructive
.finalizeXof(outLen)	Uint8Array	Variable-length digest, non-destructive
.finalizeAndReset()	Uint8Array	Finalize then reset (useful for batch hashing)
.reset()	void	Reset to initial state, preserves mode
.free()	void	Release WASM memory manually (prefer using instead)

Memory management: In all modern browsers (and wasm-bindgen ≥ 0.2.91), WASM memory is freed automatically via the TC39 weak references proposal when the JS object goes out of scope.

In practice, you often don't need to think about this. For deterministic cleanup or environments without weak reference support (older browsers, some Node.js setups), use using (TypeScript 5.2+ / ES2026) or call .free() manually.

Never call .free() on a using-managed instance otherwise it will double-free.

Benchmarks

Tested on Apple M4, Node.js v24.

Size	@noble/hashes	awasm-noble	awasm-noble (threads)	blake3-wasm
32 B	28 MB/s	105 MB/s	94 MB/s	129 MB/s
1 KB	105 MB/s	843 MB/s	819 MB/s	568 MB/s
64 KB	102 MB/s	1,898 MB/s	1,855 MB/s	2,004 MB/s
1 MB	101 MB/s	1,943 MB/s	4,711 MB/s	1,893 MB/s
10 MB	101 MB/s	1,911 MB/s	6,456 MB/s	2,185 MB/s

Tested on Ryzen 7 5800X, Node.js v24.

Size	@noble/hashes	awasm-noble	awasm-noble (threads)	blake3-wasm
32 B	11 MB/s	34 MB/s	45 MB/s	70 MB/s
1 KB	56 MB/s	499 MB/s	526 MB/s	885 MB/s
64 KB	52 MB/s	1,729 MB/s	1,684 MB/s	2,037 MB/s
1 MB	51 MB/s	1,550 MB/s	4,036 MB/s	1,829 MB/s
10 MB	50 MB/s	1,497 MB/s	4,946 MB/s	1,877 MB/s

Security

The underlying blake3 Rust crate targets algorithmic constant time. However, the JavaScript boundary (via napi-rs or WASM) introduces non-determinism from the V8 runtime that is outside our control. For absolute security, use the blake3 Rust crate directly in a Rust program.

See also

• @noble/hashes | pure JS implementation
• awasm-noble | auditable WASM implementation
• blake3-napi | native Node.js addon, faster for large inputs