Accounts, addresses and ENS

An Ethereum address looks like a cat walked across the keyboard: 0x followed by forty characters made of digits and the letters a–f. Nobody remembers one – and one of the most profitable scams of recent years is built on exactly that.

What an address looks like#

An address always has the form 0x + 40 hexadecimal characters, for example 0x71C7…976F. It is derived from the private key in your wallet (or rather from the seed phrase). Upper- and lower-case letters in the address work as a checksum: if one character gets mistyped somewhere, the wallet notices.

One address, many networks#

The same key gives the same address on Ethereum and on EVM-compatible networks – Arbitrum, Base, Optimism, Polygon and others. Convenient, but there is a catch:

• If you send USDC to your own address on the wrong network, the money does not disappear, it is just elsewhere. Switching the network in your wallet is enough. (This applies to ordinary accounts; with a smart wallet or multisig the address on the other network may not be yours, and the money can be lost.)
• If you send it to an exchange address on a network the exchange does not support, it can be lost, or recovering it can take weeks.

So before every transfer check both the address and the network.

ENS: names instead of hexadecimal noodles#

The ENS (Ethereum Name Service) gives an address a readable name, such as jana.eth. A wallet can then send money to "jana.eth" instead of a long string.

• A name is rented for a chosen number of years, paid per year; shorter names cost more.
• If you do not pay the rent, after a 90-day grace period anyone can buy it – and money sent to that name then goes to the new owner.

Address poisoning#

Most people check only the beginning and the end of an address. That is what address poisoning builds on:

1. You send money to a colleague at 0x71C7…976F.
2. A scammer generates an address 0x71C7…976F with the same beginning and end and sends you a zero-value transaction from it.
3. Their address appears in your history. Next time you copy it from there – and the money goes to them.

On Ethereum alone people lost roughly 62 million dollars this way in December 2025 and January 2026.

Common myths#

• "My address on Ethereum and on Arbitrum is different." It is the same – only the network differs.
• "My .eth name is mine forever." Only as long as you pay the rent.
• "Checking the first and last few characters is enough." That is exactly what scammers exploit.