Public key and address

A public key is derived mathematically from a private key and can be shared safely. Others use it to verify that a signature was produced by the matching private key. In practice, people usually share an address rather than the raw public key. An address is a shorter, encoded form derived from the public key (or from a script) that tells senders where to send coins.

Bitcoin addresses come in several formats: legacy addresses starting with 1, script addresses starting with 3, and native SegWit and Taproot addresses starting with bc1. Ethereum addresses start with 0x followed by 40 hexadecimal characters.

Always double-check an address before sending, ideally by comparing the first and last several characters, because payments cannot be reversed. Some malware swaps copied addresses in your clipboard for the attacker's.