Is there a RegEx to validate a Base32 :: RFC 3548

Question

I want to validate a Base32 code before converting it. Is there a way to do this such as regular expression? I need to follow these standards by RFC 3548

Answer 1

This should do it:

^(?:[A-Z2-7]{8})*(?:[A-Z2-7]{2}={6}|[A-Z2-7]{4}={4}|[A-Z2-7]{5}={3}|[A-Z2-7]{7}=)?$

Demo

The (?:[A-Z2-7]{8})* part handles 40-bit sequences. The second part handles the final bytes as specified by the spec. Note that this pattern will accept an empty string too (0 bytes).

In PHP, use this with preg_match:

$isMatch = preg_match('#^(?:[A-Z2-7]{8})*(?:[A-Z2-7]{2}={6}|[A-Z2-7]{4}={4}|[A-Z2-7]{5}={3}|[A-Z2-7]{7}=)?$#', $input);