RFC 4648 Base32 Encoder/Decoder in Vanilla JS

#javascript #webdev #tools #encoding

Base32 encoding is everywhere — TOTP secret keys, file IDs, DNS labels. Here is a clean browser-only implementation.

Try it: https://devnestio.pages.dev/base32-encoder/

Encode

function base32Encode(input, alphabet, addPadding) {
  const bytes = new TextEncoder().encode(input);
  let bits = 0, value = 0, out = "";
  for (const byte of bytes) {
    value = (value << 8) | byte;
    bits += 8;
    while (bits >= 5) {
      out += alphabet[(value >>> (bits - 5)) & 31];
      bits -= 5;
    }
  }
  if (bits > 0) out += alphabet[(value << (5 - bits)) & 31];
  if (addPadding) while (out.length % 8 !== 0) out += "=";
  return out;
}

Decode

function base32Decode(input, alphabet) {
  const clean = input.toUpperCase().replace(/=+$/, "").replace(/\s/g, "");
  let bits = 0, value = 0;
  const bytes = [];
  for (const c of clean) {
    const idx = alphabet.indexOf(c);
    if (idx < 0) throw new Error("Invalid char: " + c);
    value = (value << 5) | idx;
    bits += 5;
    if (bits >= 8) { bytes.push((value >>> (bits - 8)) & 0xff); bits -= 8; }
  }
  return new TextDecoder().decode(new Uint8Array(bytes));
}