# ERC 721 ERC 721 – **the standard for [[Non-Fungible Token|non-fungible tokens]]** // **ERC-721** || **ERC721** 1. Do you want to develop an [[Ethereum (blockchain)]] [[Decentralized Applications (dApp)|DApp]] game like [[CryptoKitties]]? Axiom Zen, a Vancouver, British Columbia, Canada based company launched it in the last week of November 2017, and by the first week of December, it went viral! Players spent millions of US dollars worth of [[Ether (ETH)|Ether]] on it within a week. In this game, players can buy, sell, and breed cute digital kittens. With the transparency that the Ethereum [[Blockchain|blockchain]] platform offers, everyone can see the rules of the game, hence the competition is fair. If you can breed rare breed of digital kittens, you can get a higher price for them. The reason I discussed [[CryptoKitties]] here is that every digital kitten in this game is a unique digital collectible. Each one commands a different price, hence you can’t use [[ERC 20]] standard for the kittens. You need a non fungible token standard, and that’s what ERC 721 is. There are other use cases too for non fungible tokens, for e.g. power distribution sector can use them. A smart contract that will interact with ERC 721 [[Token(s)|tokens]] must implement a separate interface, and hence it needs to follow the [[ERC 165]] standard. Used on [[Ethereum (blockchain)]] blockchain platform, along with [[Ether (ETH)|Ether]] token. On of many [[Ethereum Request for Comments (ERC)]].