ERC-721

ERC-721 is the Ethereum standard for non-fungible tokens, where each token has a unique identifier and is not interchangeable with any other token in the same contract. The contract tracks who owns each token ID and exposes a pointer, usually called tokenURI, to metadata describing what that ID represents: an image, a ticket, a domain name or an in-game item. Wallets and marketplaces read the same interface, which is why a token minted by one project appears in any compatible application. Two limits are worth knowing. Ownership recorded on chain proves control of the token entry itself, not automatically the copyright or legal rights to the underlying work, and if the metadata is hosted off chain it can be changed or disappear.