ERC-721 is Ethereum’s standard interface for non-fungible tokens (NFTs). It lets a smart contract track each token separately, identify its owner, and support authorized transfers. A token can represent a digital or physical item, but the standard records token-level data and transfers; it does not by itself grant copyright or prove legal ownership of an item outside the blockchain.
How ERC-721 Identifies a Token
An ERC-721 token is identified by its contract and token ID. The ownerOf method reports the current on-chain owner for an ID, and transfer methods update that record when a permitted transaction succeeds. Two token IDs in the same collection are separately tracked, unlike fungible units under ERC-20, where one unit is intended to be interchangeable with another.
“Non-fungible” describes the token’s distinct identity; it does not mean that an NFT must be an image, that every token has unique artwork, or that its market value is unique or predictable. The standard can be used for collectibles, tickets, records, or other assets, depending on the contract and the project.
Metadata and the Item an NFT Displays
The ERC-721 metadata extension is optional. When a contract supports it, tokenURI can return a URI for metadata such as a name, description, or image. That metadata and media may be stored off-chain, and the standard allows a URI to change. A token’s on-chain transfer history can therefore remain available even if a website, image host, or metadata link changes or stops responding.
Check the contract, token ID, metadata location, and any applicable license or terms before treating an NFT as ownership of artwork or a real-world asset. A token balance alone does not establish rights that the contract or governing documents do not provide.
How It Differs from Other Token Standards
ERC-20 is designed for fungible tokens with interchangeable units. ERC-721 tracks individually identified tokens. ERC-1155 offers a different interface that can manage multiple token types, including fungible and non-fungible items, within one contract. These standards serve different needs; a project’s label does not tell you whether its implementation is secure or what rights it grants.
Social Media Sentiment
A November 3, 2025 r/web3 discussion asked whether using ERC-721 creates a separate fee and how deployment costs work across networks. Replies focused on the distinction between the open standard and network gas costs. It is a small, dated question-and-answer thread that illustrates a practical point of confusion, not a measure of current community opinion.
Last updated: 2026-10
Related Terms
See Also
- OpenSea’s Trading Cards Tab: What Do You Actually Own?
- NFTs and Digital Game Ownership: What Actually Changes (And What Doesn’t)
- Why Calling It a Wallet May Have Been Crypto’s Biggest Mistake
- Exchange crypto with ChangeNOW
Sources
- Ethereum Improvement Proposal 721: Non-Fungible Token Standard — defines the ERC-721 ownership, transfer, approval, and optional metadata interfaces.
- Ethereum Improvement Proposal 20: ERC-20 Token Standard — provides the fungible-token interface used for comparison with separately identified ERC-721 tokens.
- Ethereum Improvement Proposal 1155: Multi Token Standard — describes a separate token interface that can handle multiple token types in one contract.
- r/web3: ERC-721 deployment questions, November 3, 2025 — documents a user’s question about standard-related fees and network deployment costs.