FNV-1 and FNV-1a Hash Generator

What is FNV?

FNV is a family of small, fast, non-cryptographic hashes named after Glenn Fowler, Landon Curt Noll, and Kiem-Phong Vo. This tool offers FNV-1 and FNV-1a at both 32-bit and 64-bit widths.

Hash typed text or uploaded files. Results include the unsigned value, fixed-width hexadecimal, and the raw digest bytes.

Why the ordering matters

FNV-1 and FNV-1a differ by exactly one thing: the order of two operations. FNV-1 multiplies the running hash and then XORs in the next byte. FNV-1a XORs first and then multiplies.

That single swap produces entirely different values, and the two are not interchangeable. FNV-1a is generally the one people mean and the one with better distribution on short inputs, but if you are matching an existing system, read its documentation carefully, because the names differ by two characters and the failure mode is a hash that simply never matches.

Are there alternatives?

Fast Hashes covers MurmurHash3, SipHash, and wyhash, which have better distribution and are the modern choice for hash tables. SipHash in particular is keyed, which protects a table against deliberately colliding keys.

CRC-32 and Adler-32 are the tools for detecting corruption. For anything cryptographic, use BLAKE3, SHA3, or SHA256.

Fun facts and more info

FNV's appeal is that it is almost nothing: a multiply and an XOR per byte, no tables, no setup, a few lines in any language. That is why it turns up embedded in file formats and small systems where pulling in a hash library would be absurd.

It is not cryptographic and must not be used for passwords, signatures, authentication, or integrity against an attacker. Anyone can find inputs that collide.