Address

An address is like an account number on a blockchain. It is a string of letters and numbers that others use to send you coins or tokens. Addresses are derived from a public key by hashing it and encoding the result. Bitcoin addresses commonly start with bc1, 1, or 3 and are 26 to 62 characters long. Ethereum addresses start with 0x followed by 40 hexadecimal characters.

Sharing an address is safe; it reveals nothing that lets someone spend your funds. However, blockchains are public, so anyone who knows an address can see its balance and full transaction history. For privacy, Bitcoin wallets generate a fresh address for each payment, while Ethereum users usually reuse one address.

Sending to the wrong address is the most common irreversible mistake in crypto. Addresses are format-specific: sending bitcoin to an Ethereum address, or sending tokens to a contract that cannot handle them, can lose the funds permanently. Copying addresses carefully, sending a small test amount first, and using the wallet's QR scanner all help avoid errors.