tokenURItokenId

tokenURI(tokenId) refers to a function commonly used in NFT contracts that implement the ERC-721 standard. It returns a URI that points to a JSON metadata document describing the token identified by tokenId. In the ERC-721 metadata extension, the function is declared as tokenURI(uint256 tokenId) external view returns (string memory).

The purpose of tokenURI is to provide a machine- and human-readable description of the token for wallets, marketplaces, and other clients. The metadata at the URI typically includes information such as the token’s name, description, image or media URL, and optional attributes or traits that help characterize the token.

A widespread implementation pattern is to derive the final URI from a base URI stored in the contract. For example, a contract may store a baseURI and return a string that concatenates baseURI with the tokenId, resulting in a URL like baseURI/tokenId. The URI can point to an HTTP(S) endpoint, a decentralized storage location such as IPFS, or another content-addressed resource. Some contracts compute the URI dynamically or fetch metadata via off-chain services; others keep metadata on-chain, though this is less common due to cost.

Metadata format generally follows the ERC-721 Metadata JSON Schema, with fields such as name, description, image, and attributes (an array of trait_type and value). While the standard defines the function signature and expectations, the exact content and hosting of the metadata are up to the contract and project, emphasizing interoperability and consistent token representation across platforms.