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Base32 vs Base64: when bigger overhead is the better choice

Base64 for machine-to-machine data exchange. Base32 for anything a human will type, read, or transcribe. The overhead difference (33% vs 60%) is negligible for the small payloads (a few dozen bytes) where human readability matters.

Base64 packs 6 bits per character and expands data by 33%. Base32 packs 5 bits per character and expands data by 60%. Base32 seems strictly worse, but it has one critical advantage: it's case-insensitive and avoids visually confusable characters. For data that humans type or read aloud, Base32's extra overhead is worth the usability gain.

By TechCompare · Updated

Encoding focus
Base32 vs Base64
base32-vs-base64
Category
Format Comparison
Comparing encoding schemes side by side
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How this is calculated

Base32 is used for OTP secrets (the 16-character codes you type into Google Authenticator), product license keys, and recovery codes. The RFC 4648 Base32 alphabet excludes 0, 1, 8, and 9 to avoid confusion with O, I/l, B, and g/q. Base64's alphabet includes letters in both cases, digits, +, and /, making it error-prone for human transcription. If a user is going to type the encoded value, Base32. If machines are exchanging it, Base64.

Verdict

The choice hinges on who reads the output. Base64 carries 6 bits per character at 33% overhead but mixes upper and lower case with + and /, which humans mistype. RFC 4648 Base32 drops to 5 bits per character for 60% overhead but excludes the 0, 1, 8, and 9 lookalikes. That trade makes Base32 the standard for OTP secrets and recovery codes.

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Frequently asked questions

Why do 2FA apps use Base32 for secret keys?
Because humans type those secrets. Base32 is case-insensitive and drops visually confusable characters (0, 1, 8, 9 versus O, I/l, B, g/q), so a 16-character code you read off a screen and punch into Google Authenticator survives transcription. Base64 mixes cases and includes + and /, which would turn every manual entry into a support ticket.
How much bigger is Base32 than Base64?
Base32 packs 5 bits per character versus Base64's 6, so output runs about 60% overhead versus Base64's 33%. For the payloads where Base32 earns its keep (2FA secrets, license keys, recovery codes) the data is a few dozen bytes, so the size difference is invisible. Overhead only matters at machine-scale payloads, and those should stay on Base64.
Can Base32 and Base64 values be converted to each other?
Yes, by decoding back to bytes and re-encoding. Both are reversible transforms of the same binary data, so any Base32 value decodes to bytes that re-encode as Base64 and vice versa. There's no information loss in either direction, which is why services that publish Base32 secrets also accept them pasted into Base64-only tools after conversion.

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