Base32 Encoder and Decoder
Encode text to Base32 or decode it, with the RFC 4648 alphabet used by TOTP secrets, base32hex, or Crockford's alphabet used by ULIDs.
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Input
Encode or decode Base32
Output
Result
24 characters
Base32 uses only capitals and digits, so it survives case-insensitive systems and being read aloud. TOTP secrets in authenticator apps are RFC 4648 Base32; ULIDs use Crockford's alphabet, which drops I, L, O and U.
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About this tool
Method, assumptions, practical next steps, and limits.
Why Base32 exists
Base32 uses only capital letters and digits, so it survives case-insensitive systems, file names on any file system, and being read aloud or typed from a printout. The cost is size: 60 percent larger than the input, against 33 percent for Base64. RFC 4648 section 6 defines the standard alphabet A-Z and 2-7.
Three alphabets
The authenticator app secrets behind TOTP use the RFC 4648 alphabet. base32hex, section 7 of the same RFC, keeps sort order the same as the raw bytes. Douglas Crockford's variant leaves out I, L, O and U to avoid misreading, and is what ULIDs are written in.