ERC-721

ERC-721 is a free and open standard describing how to build non-fungible tokens (NFTs) on the Ethereum blockchain. It defines a set of rules that all ERC-721 compliant tokens must follow, allowing for interoperability across different platforms and applications. The primary feature of ERC-721 tokens is that each token is unique; unlike fungible tokens where each token is identical (e.g., one ETH is the same as another ETH), each ERC-721 token has a distinct identifier, signifying its ownership of a specific asset or piece of data.

This uniqueness enables the representation of ownership of various digital and physical items, such as artwork, collectibles, virtual real estate, and even real-world assets linked to a digital token. The ERC-721 standard specifies mandatory functions that a smart contract must implement, including methods for transferring ownership, querying the owner of a token, and determining the total supply of tokens.

Key characteristics of ERC-721 tokens include:

• Non-Fungibility: Each token is unique and distinguishable from all other tokens.
• Ownership: The standard allows for the clear tracking of ownership of each token.
• Metadata: While not strictly enforced by the standard itself, ERC-721 tokens often link to metadata describing the asset represented by the token. This metadata is typically stored off-chain, often using solutions like IPFS.
• Transferability: Tokens can be transferred from one account to another.
• Interoperability: Due to the standardized interface, ERC-721 tokens can be easily integrated into various marketplaces, wallets, and decentralized applications (dApps) that support the standard.

The development of the ERC-721 standard has been instrumental in the growth of the NFT ecosystem, enabling the creation and trading of unique digital assets in a trustless and transparent manner.