FNV 1a (64-bit) is Fowler–Noll–Vo is a non-cryptographic hash function. The basis of the FNV hash algorithm was taken from an idea sent as reviewer comments to the IEEE POSIX P1003.2 committee by Glenn Fowler and Phong Vo in 1991. In a subsequent ballot round, Landon Curt Noll improved on their algorithm. In an email message to Landon, they named it the Fowler/Noll/Vo or FNV hash.

The FNV-1a means of creating non-zero FNV offset basis. This is FNV 1a 64 bit flavor. For pure FNV implementations, this is determined solely by the availability of FNV primes for the desired bit length, however, the FNV webpage discusses methods of adapting one of the above versions to a smaller length that may or may not be a power of two.

One of FNV's key advantages is that it is very simple to implement. Start with an initial hash value of FNV offset basis. For each byte in the input, multiply hash by the FNV prime, then XOR it with the byte from the input. The FNV-1a algorithm reverses the multiply and XOR steps.