What is ENS?

The ENSENS, the Ethereum Name Service, is a naming system that maps readable names like alice.eth to addresses.See it in the glossary Read the explainer is a naming system that lets you use short names like alice.eth instead of long AddressAn address is the public identifier of a wallet or contract on Ethereum, a long string starting with 0x.See it in the glossary. A raw address is 42 characters of letters and numbers, and one wrong character sends money to the wrong place. You register a name once and point it at an address. Wallets and apps do the lookup for you, so you only see the name.

Two cards joined by an arrow. On the left, the name vitalik.eth. On the right, the address 0xd8dA...6045. The arrow says ENS looks it up, like a phone book turning a contact name into a number. — ENS turns a name people can say into the address a wallet needs.

The phone book is not a website or a company database. It is a set of Smart contractA smart contract is a program stored at an address on the blockchain that anyone can call and that runs exactly as written.See it in the glossary Read the explainer on Ethereum, and the rules for who can register, change or sell a name are written into them. Reading it needs no account, and the same name works in every wallet and app that supports ENS.

How does an ENS name work?

An ENS name works by lookup: the system finds the entry for the name, then reads the details stored there, such as its address.

ENS now has two versions. In the current one, ENSv2, names sit in registries that link to each other. A name like sub.alice.eth is a chain of entries, followed from the top down. One entry point, the Universal Resolver, follows that chain so apps do not have to.

The original version, ENSv1, worked in two steps. A registry named the resolver for a name, and the resolver held the address. Older names keep resolving this way.

In ENSv1, names are not compared as text. ENS turns each name into a fixed-length fingerprint first, a step it calls the namehash. Wallets and libraries do this for you. The ENS Resolver tool looks up a name’s address record using that original registry and resolver, one read after the other.

A resolver can hold more than one address. It can also hold text records, such as an avatar picture, a website or a social handle. This is how a profile page can pull your photo from your name alone.

Is a .eth name an NFT?

A .eth name is an NFT: a token that you own and can transfer. Your WalletA wallet is the app or device that holds your keys and lets you sign transactions and view your assets.See it in the glossary shows it next to your other tokens.

Two token types exist, because ENS changed versions. New names are ERC-1155 tokens held in a registry contract, with a single owner per token. Older names are ERC-721 tokens in a contract called the Base Registrar, and some names may still be of this older kind. You can learn the shape of both standards in ERC-721 vs ERC-1155. For an older name, the token number is the hash of the name’s first part. For vitalik.eth that part is vitalik.

Owning the token means you control the name. You can set where it points, create sub-names under it, or sell it on an NFT marketplace.

Two cards for the name vitalik.eth. On the left, who owns the name, the owner, shown as 0x2208...3a9d. On the right, where the name points, the address record, shown as 0xd8da...6045. A caution note says the two answers can differ. Both read live on 2026-11-11. — Who owns a name and where it points are two records, and they can be different addresses.

The owner is whoever holds the token. The address a name points to is a record the owner chose to write, and the owner can change it later. For vitalik.eth, an older name, the two differ. On 2026-11-11 at block 26,392,402, the token was held by one address, while the name pointed to another. A name is a label, not a wallet.

Primary names: going from address to name

A primary name is the name an address chooses to be shown as. You start from an address and get a name, which is how an explorer or wallet can display vitalik.eth instead of a hex string.

Two records must agree for a primary name to count. The address has to name itself, and the name has to point back to that address. Apps check both, and a careful app shows the raw address if they do not match.

The check matters because anyone can claim any name for their own address. Without the round trip, a stranger could make their address display as someone else. The developer guide on ENS reverse lookups covers the check in code.

What does an ENS name cost, and why does it expire?

A .eth name is rented, not bought outright. You register it for as many years as you pay for, and you must renew before it runs out. The ENS documentation lists 8 US dollars per year for names of five or more letters. Registering for several years at once costs less per year. You pay in USDC or DAI.

Anyone can renew a name, not only the owner. Renewing does not change who owns it.

A timeline in four parts: Registered, until the expiry date. Grace period, 28 days to renew. Price falls, 21 days with a premium that halves daily. Open to anyone, at the normal price. — After expiry, the owner gets a 28 day grace period before the name opens up again.

When a name expires, the owner does not lose it at once. The ENS documentation describes a 28 day grace period, and a temporary premium starts after it. The premium starts very high and halves each day until it reaches zero. It lasts 21 days. After that, the name costs the normal price.

Because a name can lapse, an old name can end up with a new owner. If you rely on a name for payments, set a reminder to renew it. The ENS app shows the expiry date.

See it on a real contract

The card reads the address record for vitalik.eth from an ENS resolver contract. Open the ENS Resolver with the example vitalik.eth to see the resolver found by the original registry, and then the address record read from it.

Address that vitalik.eth points to

Reading live from Ethereum

Resolve vitalik.eth in the ENS Resolver

Show the query

resolver.addr(sel.namehash("vitalik.eth"))

Common mix-ups

“An ENS name is a username on a website.” It is a record in public contracts. No company holds a password for it, and you control it with the wallet that holds the token.
“The name and the address are the same thing.” They are two records. The owner can point the name at any address and change that later.
“If I pay for a name once, it is mine forever.” A .eth name is registered for the years you pay for. It expires unless someone renews it.
“A name in my wallet’s send box is always the right person.” Lookalike names exist. Check the address under the name and send a small test amount first when the sum is large.

Summary

ENS is a public phone book on Ethereum that links readable names to wallet addresses.
A .eth name is an NFT you own, and the address it points to is a separate record you can change.
Names are rented for the years you pay for, so renew before yours expires.

For developers

You can resolve names to addresses, and addresses back to names, with one evmquery request. The guide on ENS reverse lookup without an indexer covers both directions, including the round-trip check.

What is ENS? Ethereum Name Service explained