In one sentence
A blockchain address is a short public identifier, usually derived from a public key by hashing, that tells the network where units or tokens are recorded.
How it works
An address is to a public key roughly what a postcode is to a full street description: shorter, easier to share, and built so that mistakes are caught.
In Bitcoin, the classic address type takes the public key, hashes it with SHA-256 and then RIPEMD-160, and encodes the 20-byte result in a format called Base58Check; these addresses start with "1". Newer formats defined in BIP-173 and BIP-350 use an encoding called bech32 and start with "bc1". In Ethereum, the address is the last 20 bytes of the Keccak-256 hash of the public key, written as "0x" followed by 40 hexadecimal characters. EIP-55 adds a checksum by switching some letters to capitals.
The checksums matter because transfers are generally irreversible. If you mistype one character, software that checks the checksum will notice that the address is invalid and refuse it, rather than sending to a string that nobody controls.
Addresses are pseudonymous. They contain no name, but every transaction to and from them is permanently public. Once an address is linked to a person — through a service, a post, or a pattern of payments — its whole history becomes readable. For this reason many wallets create a new address for each incoming payment.
A simple example
Two people send the same amount to an address that differs in one character. The first copy-pastes it and the checksum matches. The second types it by hand, swaps one letter, and the wallet immediately flags the address as invalid. The checksum did not make the payment safe — it only made a typing slip visible before anything was sent.
Common misconception
Misconception: An address is an account at a company, so someone can reverse a payment sent to the wrong one.
In fact: On a public blockchain there is no operator who can undo a transfer. If units are sent to an address nobody controls, they are normally out of reach for good.
Where you meet it
- Every transaction names the addresses involved.
- Smart contracts and tokens have addresses too.
- Information exchanged under the travel rule includes them.
Related cards
Sources
This card explains a technical concept for general education. It is not a recommendation to acquire, sell or hold any crypto-asset, and it is not financial advice.