ERC-721 Non-Fungible Token Standard

INTRODUCTION

What is a Non-Fungible Token?

A Non-Fungible Token (NFT) serves as a unique identifier for items or individuals. It's ideal for platforms featuring collectibles, access keys, lottery tickets, and numbered seating for events such as concerts or sports games. Due to the versatility and potential of this token type, the ERC-721 standard was established.

What is ERC-721?

ERC-721 provides a standardized approach to NFTs. Essentially, each token is distinctive and may differ in value from another token within the same Smart Contract, possibly due to age, rarity, or even its appearance. Indeed, appearance!

Each NFT is associated with a unique uint256 identifier known as the tokenId. In the context of an ERC-721 Contract, the combination of the contract address and the uint256 tokenId is globally unique. Therefore, a decentralized application (dapp) can convert the tokenId into a visual representation, such as images of zombies, weapons, skills, or even endearing cats!

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A Quick Summary

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BODY

ERC-721, also known as Ethereum Request for Comments 721, was introduced by William Entriken, Dieter Shirley, Jacob Evans, and Nastassia Sachs in January 2018. It's a Non-Fungible Token Standard that creates an API for tokens within Smart Contracts.

The standard offers functionalities such as token transfers between accounts, retrieving an account's current token balance, determining a specific token's owner, and ascertaining the total token supply available on the network. Furthermore, it has provisions that allow an account's token amount to be moved by a third-party account upon approval.

To be recognized as an ERC-721 Non-Fungible Token Contract, a Smart Contract must implement specific methods and events. Once deployed, this contract maintains a record of tokens produced on the Ethereum platform.

From EIP-721:

Methods

• Various functions to manage tokens, including transferring, approval, and querying.

Events

• Notifications of token transfers and approvals.

CryptoKitties Contract extends beyond the standard and includes unique Events, such as "Pregnant" and "Birth".

POPULAR NFTS

• Etherscan NFT Tracker: Lists top NFTs on Ethereum by transfer volume.
• CryptoKitties: Dive into a game that revolves around breedable, collectible, and utterly adorable creatures known as CryptoKitties.
• Sorare: Engage in a worldwide fantasy football game, collecting limited edition items, managing teams, and competing for rewards.
• The Ethereum Name Service (ENS): Securely and decentralizedly address resources, whether on or off the blockchain, using intuitive names.
• POAP: Attain free NFTs by attending events or fulfilling specific actions. Creating and distributing POAPs is cost-free.
• Unstoppable Domains: A San Francisco initiative that establishes domains on blockchains. Blockchain domains transform cryptocurrency addresses into easily decipherable names and can facilitate censorship-resistant web spaces.
• Gods Unchained Cards: Engage in a TCG on the Ethereum blockchain, leveraging NFTs to grant genuine ownership to in-game elements.

Bored Ape Yacht Club: A set of 10,000 distinct NFTs that not only symbolize rare art but also grant membership to an exclusive club. This membership yields privileges that expand as the community's contributions grow.