fast-base64

fast-base64

Base64 encoding/decoding optimized for speed. Converts base64 to and from Uint8Array.

• Hand-written in WebAssembly text format for small size.
• Uses SIMD instructions if the Browser supports it.
• Compatible with node and deno.
• ~20x faster than the fastest JS implementation on the first 100kB of input
• ~2-3x faster than the fastest JS on the first 100MB
• The fastest existing JS implementation is the one shipped in this package

npm install fast-base64

import {toBytes, toBase64} from 'fast-base64';

let bytes = await toBytes('SGVsbG8sIHdvcmxkIQ==');
let base64 = await toBase64(bytes);

Alternative exports

We support three versions of the library that have different speed and size trade-offs

• fast-base64: The default is the fastest version, 1.9kB minzipped, async API
• fast-base64/small: Version without SIMD, 1.0kB minzipped, async API, no node support, 2-3x slower
• fast-base64/js: Fastest pure JS version, 600 bytes minzipped, sync API, 2-30x slower

Example for using the pure JS version:

import {toBytes, toBase64} from 'fast-base64/js';

let bytes = toBytes('SGVsbG8sIHdvcmxkIQ=='); // no `await`!
let base64 = toBase64(bytes);

Base64 URL

To support base64url we offer two tiny, fast helper functions (the runtime overhead compared with base64 transcoding itself is negligible):

import {toUrl, fromUrl} from 'fast-base64/url';

let base64url = toUrl('/+A='); // "_-A"
let base64 = fromUrl(base64url); // "/+A="

// you could make our own helper functions for base64url
const toBase64Url = async bytes => toUrl(await toBase64(bytes));
const toBytesUrl = async base64url => await toBytes(fromUrl(base64url));

Curious about Base64?

In making this package, I tried many different approaches for base64 encoding, including using the native atob() and btoa() functions and native dataURI functionality. You can find 4 alternative encoding and 3 decoding methods here: https://github.com/mitschabaude/fast-base64/blob/main/base64-alternative.js

Turns out that one of the fastest bytes to base64 implementations in JS uses the good old FileReader API!

async function toBase64DataUri(bytes) {
  let reader = new FileReader();
  let promise = new Promise(resolve => {
    reader.onload = () => resolve(reader.result);
  });
  let blob = new Blob([bytes.buffer], {type: 'application/octet-stream'});
  reader.readAsDataURL(blob);
  return (await promise).replace('data:application/octet-stream;base64,', '');
}