ERC-721 is the Ethereum standard for non-fungible tokens — assets that are individually distinguishable rather than interchangeable. It defines ownership, transfer and approval for unique token IDs, and a metadata extension pointing at the content a token represents.
ERC-721
ERC-721 did for unique assets what ERC-20 did for fungible ones: a common interface, so a wallet or marketplace can display and move an item it has never seen. The metadata extension — a URI per token — is where the asset’s actual content lives, and where most of the durability questions sit.
- Per-token identity - Ownership tracked by token ID rather than by balance.
- Approvals per token or per operator - Delegation at two granularities, both worth understanding before signing one.
- A metadata URI - The token points at its content; whether that pointer survives is a property of where it points.
- Marketplace interoperability - Any conforming marketplace can list any conforming token.
The consumer end of this market is also its weakest published surface: The State of Blockchain & Crypto APIs scores NFT, gaming and consumer web3 at 20.5 with 29.3% publishing a machine-readable contract — the widest gap between public attention and published evidence in the catalog, in the segment built directly on this standard.
Referenced in API Evangelist papers
This standard shows up in my published research. These reports read the machine-readable evidence provider by provider — and put this standard in the context of a real sector.
The State of Blockchain & Crypto APIs
The standard under the market's weakest-published segment — NFT, gaming and consumer web3 at 20.5, with 29.3% publishing a contract.
