ERC-721
The Ethereum standard for non-fungible tokens, giving each one a unique identifier so no two are alike.
ERC-721 is the standard that made NFTs work. Where ERC-20 tokens are interchangeable, ERC-721 gives every token a unique ID, so a contract can track individual items and owners. CryptoKitties popularized it in 2017; most NFT art uses it today.
The standard defines how ownership transfers and how marketplaces read a token's metadata, the link to its image and traits. That shared interface is why an NFT minted in one app shows up correctly in another wallet.
A related standard, ERC-1155, lets one contract manage both fungible and non-fungible tokens, which gaming projects favor.
Related terms
A blockchain token that represents ownership of a unique item, where no two units are interchangeable.
ERC-20The Ethereum standard that defines how fungible tokens behave, letting wallets and apps support them uniformly.
MintingThe act of creating a new token or NFT and writing it onto a blockchain for the first time.
Floor PriceThe lowest price at which any item in an NFT collection is currently listed for sale.