ENS Name Lookup

Resolve an ENS name to its Ethereum address, or reverse-resolve an address to its ENS name.

How It Works

The Ethereum Name Service (ENS) maps human-readable names like vitalik.eth to machine-readable Ethereum addresses, and vice versa. It works similarly to DNS for the internet, but runs entirely on the Ethereum blockchain.

Forward Resolution

When you enter an ENS name, this tool performs two on-chain lookups:

1. Find the Resolver — Queries the ENS Registry contract to find which resolver contract is responsible for the name.
2. Resolve the Address — Calls the resolver's addr() function with the namehash of the ENS name to retrieve the Ethereum address.

Reverse Resolution

Given an Ethereum address, the tool looks up whether an ENS name has been set as the primary name (reverse record) for that address:

1. Compute Reverse Node — Constructs the reverse lookup name: <address>.addr.reverse.
2. Query Resolver — Finds the resolver for the reverse node from the ENS Registry.
3. Get Name — Calls the resolver's name() function to retrieve the primary ENS name.

Namehash Algorithm

ENS uses a recursive hashing algorithm called namehash to convert domain names into a fixed-length identifier (bytes32). The name is split by dots, and each label is hashed with Keccak-256, then combined right-to-left:

namehash("")          = 0x00...00
namehash("eth")       = keccak256(namehash("") + keccak256("eth"))
namehash("vitalik.eth") = keccak256(namehash("eth") + keccak256("vitalik"))

Key Contracts

• ENS Registry — 0x00000000000C2E074eC69A0dFb2997BA6C7d2e1e — the central registry that maps namehashes to their resolver and owner.
• Resolver — Each name can point to its own resolver contract, which stores the address, content hash, text records, and other data.