I have been trying to implement my own SHA3 256 function in python to try and learn and understand how it works. I have been comparing my hashes with an online sha3 tool found here https://emn178.github.io/online-tools/sha3_256.html and the test files on the NIST website found here https://csrc.nist.gov/projects/cryptographic-standards-and-guidelines/example-values.
I realised that the output hash found in the 1600 bit file found on the NIST file is different from the one on the online tool. I have even used a python sha3 library and the result of the hash is the same as the one on the online tool.
Does anyone know why the NIST output hash is different? I know NIST has made some changes to SHA3 padding but I am still unsure.