Definition

ERC-721

The Ethereum standard for non-fungible tokens (NFTs) — unique tokens where each has a distinct ID and metadata, used for digital art, collectibles, and identity.

Released in 2018 alongside CryptoKitties, ERC-721 added the concept of unique tokens. Each token has its own ID, can have its own URI pointing to metadata (image, audio, etc.), and ownership transfers function similarly to ERC-20 but with token-ID granularity.

ERC-1155 (released 2018) added "semi-fungible" tokens — useful for game items where you might own 50 copies of the same sword. ERC-721 remains dominant for art/collectibles where uniqueness is the point.

Why it matters

ERC-721 is the technical foundation of the NFT category. Understanding it clarifies what NFT ownership actually represents on-chain.

How CryptoRadar24 tracks it

CryptoRadar24 references NFT-related events through broader market trend reporting; we don't track individual NFT collections.

Related terms

NFT (Non-Fungible Token)
A unique cryptographic token representing ownership of a specific digital or physical item, distinct from interchangeable tokens like BTC or ETH.
Smart contract
Self-executing code deployed on a blockchain that runs deterministically when called, without requiring an intermediary.
ERC-20
The Ethereum standard for fungible tokens — interchangeable units like USDC, UNI, AAVE, where every token of a given type is identical.

FAQ

What's the difference between ERC-721 and ERC-1155?

ERC-721 is one-token-one-ID. ERC-1155 supports both fungible and non-fungible tokens in the same contract — more efficient for games where you need both.

Can ERC-721 metadata be changed?

The token URI can be updated by whoever has admin rights (often the contract deployer). The off-chain metadata it points to is even more mutable. "Immutable NFT" is mostly aspirational unless explicitly designed.

What is the gas cost of minting an ERC-721?

Highly variable — typically $5-50 on Ethereum mainnet during normal congestion, $50-200 during NFT-launch peaks. L2 minting costs <$1.

Are all NFTs ERC-721?

On Ethereum mostly yes, with some ERC-1155. On Solana and other chains, equivalent standards exist (Solana SPL, Bitcoin Ordinals).