The Ethereum Name Service is a distributed, open naming system built on the Ethereum blockchain. It maps human-readable names like 'alice.eth' to machine-readable identifiers such as cryptocurrency addresses and content hashes, operating on a hierarchical domain structure similar to DNS.

ENS enables reverse resolution, allowing metadata to be associated with addresses. Domain owners have full control over their subdomains, and top-level domains are governed by registrar smart contracts. The system is deployed on the Ethereum mainnet and testnets, with compatible applications automatically detecting the correct network deployment.