What Is Base32? (And Why It's Different from Base64)

Short answer

Base32 encodes arbitrary binary data using just 32 ASCII characters: A–Z and 2–7. It's bigger than Base64 (uses 32 symbols instead of 64), but it has one important advantage — it's case-insensitive and avoids ambiguous characters (0/O, 1/I/L) — making it ideal for systems where users type the value, like TOTP authentication secrets and QR codes.

The Base32 alphabet (RFC 4648)

Index	Char	Index	Char
0	A	16	Q
1	B	17	R
2	C	18	S
3	D	19	T
4	E	20	U
5	F	21	V
6	G	22	W
7	H	23	X
8	I	24	Y
9	J	25	Z
10	K	26	2
11	L	27	3
12	M	28	4
13	N	29	5
14	O	30	6
15	P	31	7

Base32 vs Base64 — practical differences

	Base32	Base64
Alphabet size	32 chars	64 chars
Characters used	A-Z, 2-7	A-Z, a-z, 0-9, +, /
Output size	~60% larger than input	~33% larger than input
Case-sensitive?	No (a=A)	Yes (a≠A)
Ambiguous chars?	No (avoids 0,1,8,9 entirely)	Yes (0/O, 1/l/I)
URL-safe?	Yes	Standard variant has /+ — needs Base64URL variant
Best for	Human-typed secrets, QR codes	Binary in text contexts (HTTP headers, JSON)

Where you'll encounter Base32

• TOTP / 2FA secrets — Google Authenticator, Authy, 1Password all use Base32 for the shared secret seed because users sometimes type it manually
• Onion services — Tor v3 onion addresses are Base32-encoded
• QR codes for short content — case-insensitive Base32 simplifies scanner correction
• Voice transmission — radio operators, customer-service phone codes — Base32 over a phone line works (no homonyms to confuse)
• DNS labels — DNS is case-insensitive; Base32 fits the constraint

Padding

Base32 output length is always a multiple of 8 characters. If the input doesn't divide evenly, the result is padded with = characters. Some implementations omit the padding (RFC 4648 allows both with/without).

Variants

• RFC 4648 Base32 — the standard (alphabet shown above)
• Crockford Base32 — different alphabet (excludes I, L, O, U); more human-friendly when read aloud
• z-base-32 — used in cryptography; reorders alphabet so common values get more readable letters
• Base32hex — extension that preserves sort order (rare, niche)

Common confusion

If a user reports a TOTP secret "doesn't work" but everything looks fine, they probably typed an O instead of 0 or I instead of 1. Base32 specifically excludes both ambiguous pairs to prevent this — but only if the system rejects those characters during entry.

Related tools

For Base64 (the more common encoding for binary in text contexts): Base64 encoder/decoder. Generate QR codes that use Base32-style content: QR code generator. Hash secrets before encoding: hash generator.