December 27, 2021

How to create and deploy an ERC-721 (NFT)


Digital collectibles compatible with the ERC-721 standard have become very popular since the launch of Cryptokitties and have moved forward towards mass adoption in recent months. This guide will cover creating and deploying our very own ERC-721 (NFT) using the 0xcert/ethereum-erc721 smart contract library.

What is a Non-Fungible Token?

Fungible means to be the same or interchangeable. For example, Ethereum tokens, all the members of a particular token class, have the same value. The same can be said of Cardano tokens. Fungible tokens are interchangeable 1:1.

With this in mind, NFTs are unique; each one is different. Every single token has unique characteristics and values. The types of things that can be NFTs are collectible cards, artworks, airplane tickets, etc. They are all clearly distinguishable from one another and are not interchangeable. Think of Non-Fungible Tokens (NFTs) as rare collectibles; each has unique characteristics, unusual attributes, and most times, its metadata.

What is ERC-721?

ERC stands for Ethereum Request for Comment, and 721 is the proposal identifier number. ERCs are application-level standards in the Ethereum ecosystem, they can be a smart contract standard for tokens such as ERC-20, the author of an ERC is responsible for building consensus with the Ethereum community and once the proposal is reviewed and approved by the community it becomes a standard. You can track the recent ERC proposal here. ERC-721 was created to propose the functionality to track and transfer NFTs within smart contracts.

ERC-721 is an open standard that describes how to build Non-Fungible tokens on EVM (Ethereum Virtual Machine) compatible blockchains; it is a standard interface for Non-Fungible tokens; it has a set of rules which make it easy to work with NFTs. NFTs are not only of ERC-721 type; they can also be ERC-1155 tokens.

The following are the set of functions and events defined in the ERC-721 standard:

ERC-721 defines some functions with compliance to ERC-20. This makes it easier for existing wallets to display simple token information.

ERC20-like Functions:

  • name: Used to define the token’s name, which other contracts and applications can identify.

  • symbol: Used to define token’s shorthand name or symbol.

  • totalSupply: This function is used to define the total number of tokens on the blockchain; the supply doesn’t have to be constant.

  • balanceOf: Returns number of NFTs owned by an address.

Ownership Functions

  • ownerOf: This function returns the address of the owner of a token. As each ERC-721 token is unique and non-fungible, they are represented on the blockchain by an ID. Other users, contracts, apps can use this ID to determine the owner of the token.

  • approve: This function grants or approves another entity the permission to transfer tokens on the owner’s behalf.

  • takeOwnership: This is an optional function that acts like a withdraw function since an outside party can call it to take tokens out of another user’s account. Therefore, takeOwnership can be used when a user has been approved to own a certain amount of tokens and wishes to withdraw said tokens from another user’s balance.

  • transfer: This is another type of transfer function; it allows the owner to transfer the token to another user, just like other digital tokens/coins.

  • tokenOfOwnerByIndex: This is an optional but recommended function. Each owner can own more than one NFT at the same time. Its unique ID identifies every NFT, and eventually, it can become difficult to keep track of IDs. So the contract stores these IDs in an array and the tokenOfOwnerByIndex function lets us retrieve this information from the array.

Metadata Function

  • tokenMetadata: This optional feature is an interface that lets us discover a token’s metadata or a link to its data.


  • Transfer: This event is fired when the ownership of the token changes from one individual to another. It emits the information on which account transferred the token, which account received the token, and which token (by ID) was transferred.

  • Approve: This event is fired when a user approves another user to take ownership of the token, i.e., it is fired whenever approve function is executed. It emits the information on which account currently owns the token, which account is approved to take ownership of the token in the future, and which token (by ID) is approved to have its ownership transferred.

Use cases of Non-Fungible Tokens (NFTs):

  • Digital art (or physical art): Art pieces are the most popular use cases of NFTs. Digital art auctions were the first application of NFTs and continue to grow.

  • Gaming: Providing in-game purchases and collectibles of games.

  • Real estate: Tokenizing properties and smart contracts and carry buying and selling.

  • Finance: Financial instruments like loans, futures, and other responsibilities. 

  • Software titles: Software licenses to ensure anti-piracy and privacy.

  • Concert tickets/Sports match tickets: To ensure that no fraud happens in ticket selling and fans can have a single place to view past experiences.

  • KYC compliance: Creating a token for a specific user’s KYC.

Getting test ETH

Now that we know what ERC-721 tokens are and how they work let’s see how we can build and deploy our own tokens.

We’ll deploy our contract on the Ropsten testnet. To get started, you will need the Metamask browser extension to create an ETH wallet and some test ETH, which you can get by going to the Ropsten faucet. You'll need to select Ropsten Test Network on your Metamask wallet and copy-paste the wallet address into the text field in the faucet, then click Send me test Ether.

Adding Files to IPFS

Before writing our NFT contract, we need to host our art for NFT and create a metadata file; for this, we’ll use IPFS - a peer-to-peer file storing and sharing distributed system. Download and install IPFS CLI  based on your Operating system by following the installation guide in IPFS docs.  
Following are the steps for hosting the image and metadata file.
Step 1: Creating IPFS repo.
Start the IPFS repo by typing the following in a terminal/cmd window.
$ ipfs init
Step 2: Starting the IPFS daemon.
Start IPFS daemon, open a separate terminal/cmd window and type the following.
$ ipfs daemon
Step 3: Adding an image to IPFS 
Go to the first terminal window and add the image to IPFS (art.png here).
$ ipfs add art.png
Copy the hash starting from Qm and add the “” prefix to it; it must look something like this
Step 4: Adding JSON file to IPFS
Create a JSON file nft.json and save it in the same directory as the image. 
JSON file format: 

    "name": "NFT Art",
    "description": "This image shows the true nature of NFT.",
    "image": "",

Now add the JSON file. 
$ ipfs add nft.json
Copy the hash starting from Qm and add the “” prefix to it; it must look something like this
Save this URL. We'll need this to mint our NFT.

Creating our own token.

For ease and security, we’ll use the 0xcert/ethereum-erc721 contract to create our NFT. With 0xcert/ethereum-erc721, we don’t need to write the whole ERC-721 interface. Instead, we can import the library contract and use its functions.
Head over to the Ethereum Remix IDE and make a new Solidity file, for example - nft.sol
Paste the following code into your new Solidity script:

// SPDX-License-Identifier: MIT
pragma solidity 0.8.0;
import "";
import "";
contract newNFT is NFTokenMetadata, Ownable {
  constructor() {
    nftName = "Synth NFT";
    nftSymbol = "SYN";
  function mint(address _to, uint256 _tokenId, string calldata _uri) external onlyOwner {
    super._mint(_to, _tokenId);
    super._setTokenUri(_tokenId, _uri);

Explanation of the code above: 
Line 1: Specifying SPDX license type, which is an addition after Solidity ^0.6.8. Whenever the source code of a smart contract is made available to the public, these licenses can help resolve/avoid copyright issues. If you do not wish to specify any license type, you can use a special value UNLICENSED or simply skip the whole comment (it won’t result in an error, just a warning).
Line 2: Declaring the solidity version.

Line 4-5: Importing 0xcert/ethereum-erc721 contracts.

Line 7: Starting our Contract named newNFT and mentioning it’s extending NFTokenMetadata and Ownable contracts.

Line 9-12: Initializing the constructor and setting name, a symbol of our token.

Line 14: Declaring function mint with three arguments, variable _to of type address which will store the address of the receiver of NFT token, variable _tokenId of uint256 type which will hold the token id, variable _uri of type string which will store the URI of the JSON file. Declaring mint as external means, it can be accessed from other smart contracts and outside the self scope.

Line 15: Minting token using the address of the receiver and token id.

Line 16: Setting token URI using token id and URI of JSON file.

Compile the smart-contract and deploy it using injected Web3 (make sure to select Ropsten testnet on Metamask before compiling the contract). Approve the transaction from metamask.

If you receive an error message before deployment, “This contract may be abstract,” make sure to select the appropriate contract under the Contract tab.
Confirm the transaction in Metamask

Now go to the “Deployed Contracts” section in Remix and expand the deployed contract. You’ll see a bunch of functions/methods. Expand the mint function and add the following details:

  1. Add your Ropsten address in the _to the field.
  2. Enter any Big number value in the _tokenid field (we suggest 1 since it’s the first).
  3. Add URI of JSON file in the _uri field, which we obtained in the previous section. 

Click on transact and confirm the transaction from metamask. Now you have the token on the Ropsten chain.

You can check other details like name, symbol, owner, or tokenuri by entering the token id we mentioned earlier.


Congratulations on creating your very own NFT, help your artist friends put their artistic work on the Ethereum blockchain, or become an artist yourself. Checkout 0xcert/ethereum-erc721’s GitHub for more examples.
Subscribe to our newsletter for more articles and guides on Ethereum. If you have any feedback, feel free to reach out to us via Twitter. You can always chat with us on our Discord community server, featuring some of the coolest developers you’ll ever meet :)
Ready to try QuickNode? Start your 7-day free trial

Related articles 14

Apr 12, 2022 How to Deploy a Smart Contract on MATIC/Polygon

Ethereum is a very lovely blockchain to work with, but recently, heavy traffic and many people building on it have resulted in the chain being a bit congested. Layer 2 solutions solve this issue by extending Ethereum's scalability. Polygon (FKA MATIC) is one such...

Continue reading
Apr 12, 2022 How to build an Ethereum URL shortener dApp

dApps (decentralized applications) are an integral part of the Ethereum development ecosystem. There are thousands of dApps already residing on the Ethereum blockchain. In this guide, we will learn how to build an Ethereum dApp that...

Continue reading
Jan 31, 2022 How to Create a BEP20 Token

BEP20 is the Binance Smart Chain equivalent to the popular ERC20 specification for tokens on the Ethereum network. The difference is the BEP20 Token isn't run on the Ethereum Network, but the Binance Smart Chain network. Despite this difference, because BSC (Binance Smart...

Continue reading
Dec 27, 2021 An overview of how smart contracts work on Ethereum

Smart contracts are the first-class citizens in the Ethereum blockchain; they are a critical part of Ethereum development. In this guide, we’ll see an overview of how smart contracts work on the Ethereum blockchain. This will include how to set up an Ethereum IDE and then...

Continue reading
Mar 7, 2022 How to create and deploy an ERC20 token

Ethereum network’s launch in 2015 created a lot of buzz in the developer community and sprouted a lot of tokens on the network. Initially there weren’t any templates or guidelines for token development. This resulted in a variety of tokens quite different from each other....

Continue reading
Dec 27, 2021 How to create your own Oracle with an Ethereum smart contract

Ethereum smart contracts are the most valuable features of the Ethereum blockchain network; The development of applications driven by smart contracts on the Ethereum blockchain has skyrocketed recently. These smart-contracts are sandboxed and can’t access the data...

Continue reading
Dec 27, 2021 What is an ABI?

While interacting with a smart contract ABI is one of the essential components. In this guide, let us understand what the ABI of smart contracts is.

Continue reading
Dec 27, 2021 How to call another smart contract from your solidity code

Smart contracts are the most popular feature of the Ethereum network. Smart contracts have functions that sometimes need to be accessed by other smart contracts. Before understanding smart contracts' interactions, let's brush up on our basics about smart...

Continue reading
Dec 27, 2021 How to write an Ethereum smart contract using Solidity

This article is intended for developers new to Ethereum development. In this article, we will talk about Solidity and smart contracts, What they are and what role they actually play in the ethereum development with the end goal of writing a smart contract using...

Continue reading
Mar 14, 2022 How to Create and Deploy an ERC-1155 NFT

ERC1155 has emerged as a gold standard to create NFTs; every major marketplace lists new tokens as an ERC1155 standard. In this guide, we will learn about the ERC1155 token standard and how to create an ERC1155 token.What we will...

Continue reading
Jan 31, 2022 Como crear un Token BEP20

BEP20 es en Binance Smart Chain el equivalente al popular token ERC20 de la red de Ethereum. La diferencia es que el token BEP20 no corre en la red de Ethereum sino en la red de Binance Smart Chain. Más allá de esta diferencia, como BSC (Binance Smart Chain) implementa la...

Continue reading
Feb 12, 2022 How to Create a Smart Contract Factory in Solidity using Hardhat

Hello reader! Today we are going to be leveling up your Solidity skills. We are going to walk you through how to implement the factory contract pattern. Do not worry if you have not heard this term before; all will be explained to you by the end of the...

Continue reading
Apr 12, 2022 How to Create and Deploy a Factory ERC-1155 Contract on Polygon using Truffle

With the increasing popularity of NFTs, Polygon, a fast-growing blockchain, has become the go-to choice for many users and developers. Compared to Ethereum, Polygon allows users and developers to interact with blockchains at a more affordable level. For these reasons,...

Continue reading
Apr 12, 2022 How to Create a Dutch Auction Smart Contract

Often to perform any transaction between two untrusted parties, there is a need for a trusted middle man; smart contracts eliminate this need for a middle man altogether. In this guide, we will learn how to create a dutch auction smart contract which will make the entire...

Continue reading