Convert::Base32::Crockford - Encode/Decode Strings using Crockford Base32 Scheme

convert-base32-crockford-pm convert-base32-crockford-pm


    use Digest::SHA 'sha1';
    use Convert::Base32::Crockford;

    my $foo = "foo";
    my $digest = sha1($foo);
    my $base32 = encode_base32($digest);

    die unless $digest eq decode_base32($base32);


Base32 encoding is a human friendly way to encode binary strings. You see these encodings all the time in URLs.

The "standard" encoding scheme is RFC 4648. Convert::Base32 is an excellent module for encoding/decoding this scheme.

Douglas Crockford has proposed an alternate encoding scheme at It has many advantages, discussed below.


This module is a wrapper of Convert::Base32, with the exact same API, but using the Crockford scheme.

It exports these two subroutines:

    my $crockford_base32_string = encode_base32($arbitrary_string);
    my $arbitrary_string = decode_base32($crockford_base32_string);


From a computational perspective, the Crockford scheme offers no real advantages over RFC 4648. However, from the human/usability perspective I am convinced that the Crockford scheme is superior.

Zero is Zero

As with most numerical base encodings (like hex), Crockford counting starts at '0'. RFC 4648 counting starts at 'A', and '0' means 26. It would be very challenging for most humans to count using 4648.

ASCII Sorting

Crockford encoded strings of equal length, will sort in the same ASCII order as their numerical sort order.

Lenient Decode

The Crockford scheme allows extra characters like dash ('-') and common mistypes like 'O' for '0', when decoding. This accomodates some human error and also some human friendly formatting.

More Digits

This is a bit esoteric, but at the time of this writing, I am interested in encodings that contain at least one letter and and least one number. For a given length encoding, the Crockford scheme offers a bigger set of strings that meet this requirement than RFC 4648.


There is a similarly named CPAN module called Encode::Base32::Crockford. It uses the Crockford encoding scheme but it only works on numbers (as of the time this module was written).

Base32 and Base64 are almost always employed to encode binary strings into a human readable form. Encode::Base32::Crockford::base32_encode dies when you try to encode a string that is not string of ASCII digits.


I met Douglas Crockford at the Taiwan OSDC conference in 2010. Smart guy. Thanks for this, Douglas.

Thanks to miyagawa++ for his Convert::Base32 work.


Ingy döt Net <>


Copyright 2011-2014. Ingy döt Net.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.