What is an NFT, and what does the standard actually guarantee?
An NFT is an ownership tracking interface defined in ERC-721. In the standard's own words these tokens are distinguishable and the ownership of each must be tracked separately. We set out what the standard tracks and what it never says.
In short
The definition of an NFT is not in a marketing page but in a standard. ERC-721 describes itself as:
"a standard interface for non-fungible tokens, also known as deeds"
And it states plainly what it provides: "basic functionality to track and transfer NFTs" — tracking and transfer.
Note what is absent from that sentence: no image, no art, no copyright. The standard keeps a ledger.
What "non-fungible" means
The standard's own wording:
"NFTs are distinguishable and you must track the ownership of each one separately."
That is what it means for one token not to substitute for another. One ETH is the same as any other ETH; an NFT is not, which is why each one's owner is tracked separately.
The standard's own examples make the point: all houses are distinct, and no two kittens are alike.
The image is not inside the standard
This is the most misread part. The standard defines an address attached to the token:
"A distinct Uniform Resource Identifier (URI) for a given asset."
What sits on chain is not the image but an address. The image lives somewhere else: on a server, on IPFS, or nowhere at all.
The standard does not guarantee that address keeps working. The metadata schema mentions an "image" field, but the standard itself does not require the image to exist, to persist, or to be accurate.
What the standard never discusses: rights
ERC-721 is an ownership ledger, not a definition of legal rights. Holding the token does not confer copyright, commercial use, or any other right over the attached image. Where such a right exists it comes from the collection's own licence, not from the standard.
The only thing provable on chain is this: this token is at this address. The rest is off chain.
Risks
Biggest uncertainty How particular collections store metadata, and their rights claims, were not examined here.
- The on-chain record does not cover the image. If the address dies the token remains and the image is gone. Permanence depends on the collection's storage choices.
- Token ownership is not rights ownership. A licence is a separate document and the standard does not define it.
- Metadata can be mutable. A
tokenURImay point at a fixed file or at an address someone can change later. - Standard compliance is not a measure of trust. Following ERC-721 does not mean the contract carries no other powers (minting).
What was not examined is listed in the data status above.
Sources
This article rests on the sources below. Whether each has a permanent copy is stated next to it.
- #1
Primary source for the distinguishability definition, the track and transfer function and the `tokenURI` field: the ERC-721 standard itself.
eips.ethereum.org· our own copy· archive copy· no screenshot
Evidence chain: 1 sources
Tweets get deleted, sites go down. Below is whether a durable copy exists for each source.
Sources (1)
- #1
Primary source for the distinguishability definition, the track and transfer function and the `tokenURI` field: the ERC-721 standard itself.
“NFTs are distinguishable and you must track the ownership of each one separately.”
eips.ethereum.org/EIPS/eip-721our own copyopen in a new tab - no screenshot captured
- archived copy
- captured on Sep 5, 2026, 7:44 PM
content hash
bedd672103…65e2a1
Correction history
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Correction:
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Emphasis marker in the quotation converted to a form the markdown round trip preserves; the words of the quotation did not change.