Fletcher-32 Checksum Calculator

Build Fletcher-32 from sixteen-bit words

Fletcher-32 extends the Fletcher idea to two 16-bit sums modulo 65535. This implementation groups UTF-8 bytes as big-endian words, pads an odd final byte with a zero low byte, initializes both sums to FFFF, and places the second sum above the first in the hexadecimal result. Stating those conventions prevents hidden disagreement between otherwise reasonable implementations.

For abcde, the word sequence is 6162, 6364, and 6500 in hexadecimal, producing checksum 4ff029c7. The final 6500 demonstrates the documented odd-byte padding. Treating those pairs as little-endian words would produce a different value, so a matching name alone does not guarantee interoperable byte interpretation.

State word ordering and odd-byte padding

Fletcher-32 offers a larger accidental-error space than Fletcher-16 but remains linear, unkeyed, and inappropriate for security decisions. The exact bytes are processed in your browser. Use a standardized cryptographic hash or message authentication code when an attacker might modify data, and confirm the target format's word order, initialization, and reduction behavior before comparing checksums.