SHA-3 (Keccak)
A 2015 NIST hash standard based on the Keccak sponge construction, designed as a structural alternative to SHA-2.
SHA-3 is the hash family NIST standardised in 2015 (FIPS 202), based on the Keccak sponge construction that won the SHA-3 competition. It is not a replacement for SHA-2 (SHA-2 remains secure) but a structural alternative built on different math, so a future break of one is unlikely to apply to the other. SHA-3 supports the same digest sizes as SHA-2 (224, 256, 384, 512) and adds extendable-output functions (SHAKE128, SHAKE256) for variable-length output. Ethereum uses Keccak-256 (the pre-standardisation variant) for addresses and hashes.