ERC-721 NFT Standard

ERC-721 is Ethereum's standard for non-fungible tokens (NFTs)—unique, one-of-a-kind digital assets. Each token ID represents a distinct item: a specific artwork, a domain name (ENS), a deed, a game character. Unlike ERC-20 tokens where one equals another, ERC-721 tokens are individually tracked and valued. A single ERC-721 contract can mint 1M+ unique tokens. Each has a tokenId, an owner (wallet address), and metadata (name, image, attributes). The metadata typically lives on IPFS (decentralized storage); the contract stores only the URI pointing to it. Wallets and marketplaces query tokenURI(id) to display the token.