Base32 Encode Decode rfc 4648

What this tool does

Base32 represents data using only the uppercase letters A-Z and the digits 2-7, a set of 32 characters. It serves the same purpose as Base64 but with a narrower alphabet. Input is read five bits at a time and each group maps to one character, so eight-bit characters carry five bits of payload and the output is roughly 60 percent larger than the input, compared with 33 percent for Base64.

The reason to accept that overhead is the safety of the character set. Base32 is case-insensitive, so values survive systems that do not preserve case, and it deliberately omits characters that are easy to confuse by eye, such as 0 and O or 1 and I. That makes it suitable for values a person has to read aloud or type by hand, and for case-insensitive contexts such as DNS names and some filesystems.

The best known use is two-factor authentication. The secret key you register in an authenticator app is a Base32 string. It also appears in hash notation for some file sharing systems, in DNS-based protocols, and in licence keys that humans must enter.

When to use it

Use it to inspect or produce a TOTP secret for an authenticator app, to place binary values into case-insensitive systems, to build codes that people will type or dictate, or to read back a value stored as Base32.

Input and output examples

Notes and limitations

Base32 is an encoding, not encryption, and anyone can reverse it. A TOTP secret shown in Base32 is not protected, so treat it as a credential. Be aware that several Base32 variants exist: this tool uses the standard RFC 4648 alphabet, while Crockford Base32 and z-base-32 order their characters differently and are not interchangeable. If decoding fails, check which variant produced the value.

Frequently asked questions