Base32 Encode/Decode

Base32 uses only uppercase letters A through Z and the digits 2 through 7. That makes it longer than base64 — roughly 60% growth against 33% — but it solves problems base64 does not: the result survives systems that ignore letter case, fits inside DNS labels, can be read out over the phone, and uses no character that needs escaping in a URL.

Type the text and the page returns the standard RFC 4648 encoding, padded with "=" at the end. The process groups the input bits five at a time, since 32 is two to the fifth, and each group becomes one letter. Because eight bits do not divide evenly by five, bits are left over at the end and filled with zeros — which is where the padding comes from, keeping the final block a multiple of eight characters.

The most common use today is the secret key for two-factor authentication: the TOTP secret is handed out in base32 precisely so it fits in a QR code and can be typed by hand when the camera fails. It also shows up in Tor .onion addresses, in filenames that must be case-insensitive, and in identifiers inside DNS zones.