Parse Base64 and Base64URL like crypto-js, returns Uint8Array.

This library implements the following logic:

• Invalid characters in the input are treated as 0 (equivalent to 'A').
• When parsing Base64, the '=' in the input is treated as a terminator; it and any characters after it will be ignored.
• If the last block has only 1 character, that character will be discarded.

Built for @openccw/sb3-crypto.

Setup

npm

npm i parse-base64-like-crypto-js@latest

import parseBase64 from "parse-base64-like-crypto-js";

Other Package Managers

You can also use other package managers (e.g. pnpm or yarn) in place of npm.

jsDelivr

See https://www.jsdelivr.com/package/npm/parse-base64-like-crypto-js

<script src="https://cdn.jsdelivr.net/npm/parse-base64-like-crypto-js"></script>

UNPKG

<script src="https://unpkg.com/parse-base64-like-crypto-js"></script>

Inline

You can embed browser.min.js directly into your script.
It will define the parseBase64 function using var.

Example

// Base64
parseBase64("ABCD.EFG0 12+/+/====")

// Base64URL
// It treats '=' as 0, not as a terminator.
parseBase64("ABCD.EFG0 12-_-_====", true)

// parse Base64 from bytes
var b64 = Uint8Array.of(65,66,67,68,46,69,70,71,48,32,49,50,43,47,43,47,61,61,61,61)
parseBase64(b64)

// parse Base64 with output length
parseBase64("KzdnFCBRvq3e5516c98e2044f55d85b07a4db4a185f", false, 32)

It will return a Uint8Array.

Benchmark

> pnpm benchmark
$ node scripts/benchmark.mjs
==============================================================================
 Benchmark: parse-base64-like-crypto-js vs crypto-js
 Node.js: v26.8.1 | OS: win32 x64
==============================================================================

Scenario: Small string (32 B decoded, ~44 chars Base64)
  crypto-js (parse):                      399,466 ops/s  (   2.50 µs/op)
  crypto-js (parse -> Uint8Array):        292,563 ops/s  (   3.42 µs/op)
  parseBase64:                          7,144,176 ops/s  (    140 ns/op) -> 17.88x (vs parse) / 24.42x (vs full)

Scenario: Medium string (1 KB decoded, ~1.37 KB Base64)
  crypto-js (parse):                      114,822 ops/s  (   8.71 µs/op)
  crypto-js (parse -> Uint8Array):         87,560 ops/s  (  11.42 µs/op)
  parseBase64:                            264,885 ops/s  (   3.78 µs/op) -> 2.31x (vs parse) / 3.03x (vs full)

Scenario: Large string (64 KB decoded, ~87 KB Base64)
  crypto-js (parse):                        2,076 ops/s  ( 481.69 µs/op)
  crypto-js (parse -> Uint8Array):          1,732 ops/s  ( 577.26 µs/op)
  parseBase64:                              4,653 ops/s  ( 214.90 µs/op) -> 2.24x (vs parse) / 2.69x (vs full)

Scenario: Base64URL string (1 KB decoded)
  crypto-js (parse):                       95,224 ops/s  (  10.50 µs/op)
  crypto-js (parse -> Uint8Array):         81,858 ops/s  (  12.22 µs/op)
  parseBase64:                            285,898 ops/s  (   3.50 µs/op) -> 3.00x (vs parse) / 3.49x (vs full)

Scenario: Uint8Array input (32 B decoded, ASCII bytes)
  crypto-js (parse):                      352,035 ops/s  (   2.84 µs/op)
  crypto-js (parse -> Uint8Array):        280,866 ops/s  (   3.56 µs/op)
  parseBase64:                          8,286,401 ops/s  (    121 ns/op) -> 23.54x (vs parse) / 29.50x (vs full)

Scenario: Uint8Array input (1 KB decoded, ASCII bytes)
  crypto-js (parse):                      100,676 ops/s  (   9.93 µs/op)
  crypto-js (parse -> Uint8Array):         81,310 ops/s  (  12.30 µs/op)
  parseBase64:                            394,818 ops/s  (   2.53 µs/op) -> 3.92x (vs parse) / 4.86x (vs full)

==============================================================================
 Summary Table
==============================================================================
┌─────────┬─────────────────────────────────────────────────┬───────────────────┬──────────────────┬─────────────────┬────────────────────┬───────────────────┐
│ (index) │ Scenario                                        │ crypto-js (parse) │ crypto-js (full) │ parseBase64     │ Speedup (vs parse) │ Speedup (vs full) │
├─────────┼─────────────────────────────────────────────────┼───────────────────┼──────────────────┼─────────────────┼────────────────────┼───────────────────┤
│ 0       │ 'Small string (32 B decoded, ~44 chars Base64)' │ '399.5k ops/s'    │ '292.6k ops/s'   │ '7144.2k ops/s' │ '17.88x'           │ '24.42x'          │
│ 1       │ 'Medium string (1 KB decoded, ~1.37 KB Base64)' │ '114.8k ops/s'    │ '87.6k ops/s'    │ '264.9k ops/s'  │ '2.31x'            │ '3.03x'           │
│ 2       │ 'Large string (64 KB decoded, ~87 KB Base64)'   │ '2.1k ops/s'      │ '1.7k ops/s'     │ '4.7k ops/s'    │ '2.24x'            │ '2.69x'           │
│ 3       │ 'Base64URL string (1 KB decoded)'               │ '95.2k ops/s'     │ '81.9k ops/s'    │ '285.9k ops/s'  │ '3.00x'            │ '3.49x'           │
│ 4       │ 'Uint8Array input (32 B decoded, ASCII bytes)'  │ '352.0k ops/s'    │ '280.9k ops/s'   │ '8286.4k ops/s' │ '23.54x'           │ '29.50x'          │
│ 5       │ 'Uint8Array input (1 KB decoded, ASCII bytes)'  │ '100.7k ops/s'    │ '81.3k ops/s'    │ '394.8k ops/s'  │ '3.92x'            │ '4.86x'           │
└─────────┴─────────────────────────────────────────────────┴───────────────────┴──────────────────┴─────────────────┴────────────────────┴───────────────────┘

License

Unlicense