What Is a Non-Fungible Token (NFT)?
A non-fungible token NFT is an owned, transferable, and indivisible data record that digitally represents a linked physical or virtual asset. According to NIST, the record is created and managed by a smart contract on a blockchain.
The NFT is the blockchain record rather than necessarily being the linked asset itself. This distinction is important when interpreting what an NFT represents and what information its smart contract tracks.
What Does Non-Fungible Mean?
Non-fungible means distinguishable rather than interchangeable as an equivalent unit. Each NFT is tracked separately, allowing its ownership and transfers to be recorded individually.
An NFT can represent a link to a virtual asset, such as a digital object, or to a physical asset. The token record and the linked asset remain conceptually distinct.
Why NFTs Matter
NFTs provide a blockchain-based mechanism for associating people with digital objects. NIST also describes them as a mechanism through which representations linked to virtual and physical assets can be sold and exchanged on a blockchain.
Beginners may therefore encounter NFTs when learning about digital objects, asset transfers, smart contracts, and blockchain applications. Understanding the term also helps readers distinguish the token from its linked asset and recognize that an NFT implementation can involve technical and security considerations.
How Does an NFT Work?
A smart contract creates and manages the NFT record on a blockchain. The contract defines how the token’s ownership is tracked and how supported actions, such as transfers and approvals, are handled.
ERC-721: Non-Fungible Token Standard is a documented Ethereum example. It defines a smart-contract interface for tracking NFT ownership, transferring tokens, and approving operators. An operator is authorized through the contract to perform supported actions on behalf of a token owner.
Under ERC-721, every NFT has a unique unsigned integer token ID within its contract. The combination of the contract address and token ID uniquely identifies the NFT on an Ethereum chain. The contract address identifies the relevant smart contract, while the token ID distinguishes the NFT within that contract.
ERC-721 also defines metadata and enumeration interfaces, but these interfaces are optional. An ERC-721 implementation therefore does not have to use those optional interfaces to implement the standard’s core ownership and transfer functions.
Example: A Unique Digital Artwork NFT
Hypothetical example: Imagine that a smart contract manages a distinguishable token linked to a unique digital artwork. This is an educational example and does not describe a real NFT project.
The token might have an individual token ID within the contract. That token ID, combined with the smart contract’s address, would identify the token on the relevant Ethereum chain. The contract would separately track the token’s owner and process a supported transfer from one owner to another.
In this example, the NFT is the managed blockchain record linked to the artwork. The token and the digital artwork should not be treated as if they are the same object.
Related NFT Concepts
- Blockchain: The underlying record system on which an NFT smart contract creates and manages token records.
- Smart contract: The blockchain-based mechanism that creates and manages the NFT record and implements functions such as ownership tracking, approvals, and transfers.
- Token ownership: The ownership entry tracked separately for an NFT by its smart contract.
- Transfer: A smart-contract operation that changes the recorded ownership of a token.
- Operator approval: Authorization recorded through the smart contract that permits an operator to perform supported token actions on an owner’s behalf.
- Token ID: The identifier that distinguishes an ERC-721 NFT within its smart contract.
- Contract address: The address of the smart contract managing the token. On an Ethereum chain, the contract address and token ID work together to identify an NFT.
- Metadata: Additional descriptive information exposed through an optional ERC-721 interface. The metadata interface is not required by the standard.
- Linked asset: The distinguishable virtual or physical asset represented by the NFT record. The linked asset is conceptually separate from the token, smart contract, and blockchain network.
Common NFT Misunderstandings
An NFT is not necessarily the linked asset itself
NIST defines an NFT as a data record that digitally represents a linked asset. The token record and that asset should therefore be understood as related but distinct.
A token ID is not the complete identifier by itself
For an ERC-721 NFT, a token ID is unique within its contract. The contract address and token ID together uniquely identify the NFT on an Ethereum chain, so chain and contract context matter.
ERC-721 metadata is not mandatory
The ERC-721 metadata and enumeration interfaces are optional. Metadata should not be assumed to be a required part of every implementation of the standard.
A blockchain record does not eliminate security concerns
NIST has identified potential security concerns in NFT implementations and emphasizes systematic secure design and implementation. A blockchain-based ownership record should not, by itself, be interpreted as proof that every component of an NFT implementation is secure.
Frequently Asked Questions About NFTs
Can an NFT be transferred?
Yes. Transferability is part of NIST’s NFT definition, and ERC-721 defines smart-contract functionality for transferring tokens and tracking their ownership separately.
Can an NFT represent a physical asset?
Yes. The verified NIST definition covers NFTs linked to physical or virtual assets. The NFT remains a blockchain data record representing the linked asset.
What identifies an ERC-721 NFT?
On an Ethereum chain, the combination of the smart contract address and the token ID uniquely identifies an ERC-721 NFT. The token ID is unique within that contract.
Is metadata required for an ERC-721 NFT?
No. ERC-721 specifies metadata as an optional interface, as it does for enumeration.
Can NFTs have security risks?
Yes. In Non-Fungible Token Security | NIST, NIST identifies 27 potential NFT security issues and states that systematic secure design and implementation can address them. Security depends on the implementation rather than merely on describing a record as an NFT.
Key Takeaway
An NFT is an individually tracked blockchain data record created and managed by a smart contract and linked to a distinguishable virtual or physical asset. Its ownership can be tracked and transferred separately from other tokens.
The most important practical distinction is that the NFT record is not necessarily the linked asset itself. Readers should also consider how the smart contract and the wider implementation address security.
Educational and Financial Disclaimer
This article is for general educational and informational purposes only. It does not constitute investment, financial, legal, or tax advice.
AI-generated images used in this article are educational visual aids. They should not be interpreted as official project interfaces, products, technical diagrams, or exact real-world representations. Separately supplied verified project icons or identity assets are distinct from AI-generated educational images.