What alphabet does standard Base32 use?

RFC 4648 Base32 uses the 32 characters A through Z plus the digits 2 through 7. It deliberately omits 0, 1, 8, and 9 to avoid confusion with the letters O, I, and B, making the encoding safer to read aloud or transcribe by hand.

Why is Base32 used instead of Base64?

Base32 is case-insensitive and avoids ambiguous characters, so it survives systems that uppercase text or that humans must read and type. It is common in TOTP two-factor secret keys, DNS records, and file-sharing hashes, trading a larger size for robustness.

What is the = padding for?

Padding with the equals sign pads the encoded output to a multiple of 8 characters, which keeps fixed-size blocks aligned for streaming decoders. It carries no data and decoding ignores it, so you can usually turn it off for shorter output.

How much larger does Base32 make data?

Base32 packs 5 bits into each character, so the encoded form is about 1.6 times the size of the original bytes, or 8 characters for every 5 input bytes. That is bigger than Base64 but the extra robustness is often worth it.

What happens if I paste invalid characters?

The decoder rejects any character outside the Base32 alphabet and shows which character was invalid. Whitespace and trailing padding are stripped automatically, so wrapped or padded strings decode without manual cleanup.

Base32 Encoder and Decoder

Base32 is a binary-to-text encoding that represents data using only the uppercase letters A to Z and the digits 2 to 7. This tool encodes text into that form and decodes it back, handling padding and stray whitespace for you.

How it works

Encoding reads the input bytes as a continuous stream of bits and slices it into 5-bit groups, mapping each group to one alphabet character:

alphabet = ABCDEFGHIJKLMNOPQRSTUVWXYZ234567   (index 0..31)
take 8 bits at a time, emit a character for every 5 bits accumulated
pad the final group with zero bits, then add '=' to reach a multiple of 8

Decoding reverses this: each character becomes its 5-bit index, the bits are re-concatenated, and every full 8 bits becomes one output byte. Leftover bits from padding are discarded.

Example and tips

The text Gera Tools encodes to I5SXEYJAKRXW63DT. Because the alphabet excludes the easily confused characters 0, 1, 8, and 9, Base32 is the format behind authenticator-app secret keys: you can read it over the phone without ambiguity. If you are storing a value where length matters more than legibility, prefer Base64; choose Base32 when humans must handle the string.