fast58-js

Fast Base58 encode/decode for JavaScript and TypeScript.

fast58-js is a Solana-friendly Base58 tool for addresses, public keys, signatures, and any other byte payload that needs fast Base58 conversion.

It is the spiritual successor to bs58. It uses modern JavaScript, TypeScript types, Bun-first packaging, and focused hot-path work for even better speed.

fast58-js is zero-dependency and keeps a bs58-compatible API shape. It is JavaScript-only: the npm package is built only from packages/fast58-js/src/index.ts and ships only the allowlisted files in package.json. Rust/native benchmark code in this repository is not part of this package build or publish output.

Install

With Bun:

bun add fast58-js

With npm:

npm install fast58-js

With pnpm:

pnpm add fast58-js

With Yarn:

yarn add fast58-js

Usage

import fast58, { decode, decodeUnsafe, encode } from "fast58-js";

const input = new Uint8Array([104, 101, 108, 108, 111]);

const encoded = encode(input);
const decoded = decode(encoded);
const maybeDecoded = decodeUnsafe(encoded);

fast58.encode(input);

API

• encode(input: Uint8Array): string Encodes bytes into a Base58 string.
• decode(input: string): Uint8Array Decodes a Base58 string and throws Error("Non-base58 character") on invalid input.
• decodeUnsafe(input: string): Uint8Array | undefined Decodes a Base58 string and returns undefined on invalid input.
• default Object containing { encode, decodeUnsafe, decode }.

Runtime Support

• ESM: dist/index.mjs
• CommonJS: dist/index.cjs
• Bun export condition: dist/index.bun.mjs
• Types: index.d.ts

Package Contents

The published tarball is intentionally small and JS-only:

• dist/index.mjs
• dist/index.cjs
• dist/index.bun.mjs
• index.d.ts
• logo.png
• README.md
• package.json

Development

• bun run build Builds ESM and CommonJS outputs from src/index.ts.
• bun run bundle Builds ESM, CommonJS, and Bun-specific outputs from src/index.ts.
• bun test Runs package tests.
• bun run bench Runs a fresh bundle first, then benchmarks dist/index.bun.mjs.
• bun run package:check Rebuilds and runs npm pack --dry-run so the release contents can be inspected before publishing.
• bun run release:check Runs tests, lint, rebuilds, and checks the exact npm package contents.

Benchmark

Benchmarks were run on April 8, 2026 with:

• Bun 1.3.11
• darwin 25.3.0
• arm64
• bundled artifact under test: dist/index.bun.mjs
• external libraries: bs58/base-x, @scure/base
• methodology: 5 runs per suite, 3 samples per case, median of per-run geometric means

Overall

Combined encode+decode throughput:

| Suite | fast58-js | Best external | fast58-js vs best external | | --- | ---: | ---: | ---: | | Broad Mix | 3,762,094/s | 2,521,962/s | 1.49x | | 32B Hot Path | 1,188,114/s | 714,990/s | 1.66x | | 64B Hot Path | 273,479/s | 145,262/s | 1.88x | | Large Payloads | 8,314/s | 4,091/s | 2.03x |

Broad Mix Detail

| Library | Encode gmean | Decode gmean | Combined gmean | Encode vs bs58/base-x | Decode vs bs58/base-x | | --- | ---: | ---: | ---: | ---: | ---: | | fast58-js | 2,585,411/s | 5,474,315/s | 3,762,094/s | 1.00x | 2.23x | | bs58/base-x | 2,591,342/s | 2,454,439/s | 2,521,962/s | 1.00x | 1.00x | | @scure/base | 592,242/s | 610,631/s | 601,366/s | 0.23x | 0.25x |

32B Hot Path Detail

| Library | Encode gmean | Decode gmean | Combined gmean | Encode vs bs58/base-x | Decode vs bs58/base-x | | --- | ---: | ---: | ---: | ---: | ---: | | fast58-js | 626,666/s | 2,252,582/s | 1,188,114/s | 0.92x | 3.00x | | bs58/base-x | 680,997/s | 750,680/s | 714,990/s | 1.00x | 1.00x | | @scure/base | 295,056/s | 288,958/s | 291,991/s | 0.43x | 0.38x |

64B Hot Path Detail

| Library | Encode gmean | Decode gmean | Combined gmean | Encode vs bs58/base-x | Decode vs bs58/base-x | | --- | ---: | ---: | ---: | ---: | ---: | | fast58-js | 142,802/s | 523,738/s | 273,479/s | 1.00x | 3.54x | | bs58/base-x | 142,495/s | 148,082/s | 145,262/s | 1.00x | 1.00x | | @scure/base | 77,835/s | 76,054/s | 76,939/s | 0.55x | 0.51x |

Large Payload Detail

| Library | Encode gmean | Decode gmean | Combined gmean | Encode vs bs58/base-x | Decode vs bs58/base-x | | --- | ---: | ---: | ---: | ---: | ---: | | fast58-js | 4,276/s | 16,168/s | 8,314/s | 1.01x | 4.08x | | bs58/base-x | 4,223/s | 3,963/s | 4,091/s | 1.00x | 1.00x | | @scure/base | 2,464/s | 2,432/s | 2,448/s | 0.58x | 0.61x |

fast58-js is still the overall winner in every suite above. The current shape is deliberate: encode stays roughly at parity with bs58/base-x, while decode remains materially faster across the full range and especially strong in the 32B-64B hot path.