What Is the ERC-721 NFT Standard?
Technology can prove that a digital picture or game item is one of a kind. Behind it is an Ethereum standard called ERC-721. This beginner guide explains a foundational concept for understanding NFTs.
ERC-721 in One Definition
ERC-721 is a technical standard for creating non-fungible tokens, or NFTs, on Ethereum. ERC stands for Ethereum Request for Comments, a specification agreed upon by developers. The number 721 uniquely identifies that specification.
The key phrase is non-fungible. The NFT concept took off with this standard, which gives every token a distinct unique ID.
What Does Non-Fungible Mean?
Understanding fungible versus non-fungible makes ERC-721 easier to grasp.
Swapping your KRW 10,000 banknote for a friend's KRW 10,000 banknote leaves the value unchanged. That is fungibility, as with 1 Bitcoin. But a concert ticket for row A, seat 3, cannot be treated as interchangeable with a back-row ticket even though each is one ticket. Each is unique. This is the non-fungibility represented by ERC-721.
Each ERC-721 token therefore functions like a unique digital certificate.
Differences from ERC-20 and ERC-1155
Ethereum has several token standards. Three commonly compared standards are:
| Standard | Nature | Typical Use |
|---|---|---|
| ERC-20 | Fungible; all units identical | Exchange coins and utility tokens |
| ERC-721 | Non-fungible; each token unique | NFT art and one-of-one collectibles |
| ERC-1155 | Mixed; supports both | Game items and bulk issuance |
- ERC-20: Tokens are not distinguished from one another. It is the standard for ordinary cryptocurrency tokens, including most in the Ethereum ecosystem.
- ERC-721: One unique ID per token, used to represent a true one-of-one.
- ERC-1155: A single smart contract handles several types at once, efficiently representing distinct groups such as 100 identical swords.
Where Is It Used?
ERC-721 is used where unique ownership matters.
- Digital art and collectibles, including NFT collections.
- Limited in-game items and characters.
- Memberships and admission tickets.
- Domain names and digital certificates.
The issuing contract and subsequent ownership transfers are recorded on-chain, so anyone can examine issuance and transaction history through on-chain analysis.
Risks Beginners Need to Understand
ERC-721 is only a technical standard, not a mechanism guaranteeing value. These points deserve a candid look.
- Uniqueness ≠ high value: A unique token is not necessarily expensive or likely to appreciate. Prices depend on demand, can fluctuate greatly, and may approach 0.
- Liquidity: You may be unable to buy or sell when you want.
- Scams and counterfeit issuance: Many imitation NFTs copy famous works and issue them under another contract. Learn basic scam avoidance before trading.
- Technical limits: If the original image is on an external server, the content can break when that server disappears.
This article explains ERC-721 as a technical concept and does not recommend buying or selling any asset. It provides no price prediction or guaranteed returns. Digital assets carry substantial principal-loss risk. Study sufficiently and decide under your own judgment and responsibility.
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