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LibraryMarkets2018Design paperCorpus record

Non-Fungible Token Standard

ERC-721. William Entriken, Dieter Shirley, Jacob Evans and Nastassia Sachs.

Each token id has an owner. Transfer moves that id. An optional metadata URI points at a description. The standard does not say the description is true, or that the object exists off-chain.

A reading of the public document. Not a copy of it, and not a claim about a later network that reused the name.

A title-transfer pitch should say what a court would look at: the token, the URI, or a registry elsewhere.
Evidence
Primary paper
Re-measured
No
Assumptions
3
Records linked
1

Code

Source, repository, and what is actually hosted

  • EIP-721https://eips.ethereum.org/EIPS/eip-721
  • The source URL is not a GitHub repository. No code remote is invented.
  • Full text is not mirrored. Public availability is not a licence to copy the file onto this site.
  • Add to a reading list

01 Claim ledger

What the paper is allowed to say

Each row is a sentence already in the study. The status is the same on every row: a model claim, not a live measurement.

  1. Claim 01 · Paper model

    The defect

    ERC-20 balances are interchangeable. A deed, a ticket, or a particular object is not.

  2. Claim 02 · Paper model

    The rule

    Each token id has an owner. Transfer moves that id. An optional metadata URI points at a description. The standard does not say the description is true, or that the object exists off-chain.

  3. Claim 03 · Paper model

    How it is put together

    Uniqueness is the id, inside one contract. The owner is an address. Metadata is a pointer, not a proof.

  4. Claim 04 · Paper model

    Where the claim stops

    The token is not the object.

02 Three cuts

Observation, model, falsifier

A desk does not stop at the summary. Each claim is cut three ways, using only this study's own assumptions and checks. Nothing here is a new figure.

  1. 01 The defect

    Observation

    What the study says

    ERC-20 balances are interchangeable. A deed, a ticket, or a particular object is not.

    Model

    What has to hold

    The token is not the object.

    Falsifier

    What would retire it

    What does this id correspond to off-chain?

  2. 02 The rule

    Observation

    What the study says

    Each token id has an owner. Transfer moves that id. An optional metadata URI points at a description. The standard does not say the description is true, or that the object exists off-chain.

    Model

    What has to hold

    The token is not the object.

    Falsifier

    What would retire it

    What does this id correspond to off-chain?

  3. 03 How it is put together

    Observation

    What the study says

    Uniqueness is the id, inside one contract. The owner is an address. Metadata is a pointer, not a proof.

    Model

    What has to hold

    Metadata can change or vanish if the URI is a server.

    Falsifier

    What would retire it

    Can the metadata URI be changed, and by whom?

  4. 04 Where the claim stops

    Observation

    What the study says

    The token is not the object.

    Model

    What has to hold

    The token is not the object.

    Falsifier

    What would retire it

    What does this id correspond to off-chain?

03 Sequence

One action, as an operating tape

  1. 01Mint an id to an owner.
  2. 02Transfer the id.
  3. 03A marketplace approves an operator and transfers when a sale settles.
  4. 04What does this id correspond to off-chain?

04 Load-bearing

The argument, and where a pitch drops it

  1. Why it is still on the desk

    The cut

    A title-transfer pitch should say what a court would look at: the token, the URI, or a registry elsewhere.

    Why it carries weight

    If this cut is skipped, the paper's name is being used without the mechanism that makes the name mean anything.

    Where it is dropped

    The token is not the object.

  2. After the text

    The cut

    Markets standardised on this interface. The legal object, if any, is outside the EIP.

    Why it carries weight

    If this cut is skipped, the paper's name is being used without the mechanism that makes the name mean anything.

    Where it is dropped

    The token is not the object.

05 Register

What has to be true

  • Model · Not re-measured

    The token is not the object.

  • Model · Not re-measured

    Two contracts can both have an id 1.

  • Data · Not re-measured

    Metadata can change or vanish if the URI is a server.

06 Divergence

What happened after the paper

Markets standardised on this interface. The legal object, if any, is outside the EIP.

A later client, parameter set, or reward formula is a different object. Cite this paper for the mechanism. Cite a primary release for the network. This desk has not re-run the proof.

07 Pre-mortem

What to check before you use the idea

  4. 0 of 3 marked on this browser. A mark is a reading note, not a pass, a rating, or a recommendation.

08 Anatomy

The paper, in the order a builder needs

The problem it names

ERC-20 balances are interchangeable. A deed, a ticket, or a particular object is not.

What the design proposes

  • Uniqueness is the id, inside one contract.
  • The owner is an address.
  • Metadata is a pointer, not a proof.

How the mechanism is specified

  • Mint an id to an owner.
  • Transfer the id.
  • A marketplace approves an operator and transfers when a sale settles.

What this page does not treat as proven

  • The token is not the object.
  • Two contracts can both have an id 1.
  • Metadata can change or vanish if the URI is a server.

Why the desk still reads it

A title-transfer pitch should say what a court would look at: the token, the URI, or a registry elsewhere.

09 Lexicon

Terms, opened into the record

Token id
The integer that identifies one asset inside this contract.
Operator
An address allowed to move any of an owner's tokens in this contract.

10 Repository

Every linked record on this page

Underlined words open a page that already exists: a concept, a protocol profile, a failure record, or another paper. If a word is not underlined, this desk does not have a record for it.

This is Blockchain Lab's reading of a public design paper. It is not the paper, not a copy of it, and not an offer of tokens, equity, custody or a partnership. Later network behaviour can diverge from the text. Nothing here is investment, legal or technical advice.

Research status: Design paper. Last reviewed: 1 October 2026. This is a reading of a public paper, not investment, legal or security advice.