Deploy an ERC-721 Token

OpenZeppelin provides secure, community-vetted smart contract templates that follow best practices for ERC-721 (NFT) development.

Deployment with Foundry
Deployment with Hardhat

Step 0: Setup Foundry

If your Foundry project isn’t set up yet, please go to the Foundry setup section before proceeding.

Step 1: Create the ERC-721 Contract

Create a contract script in src/MyERC721.sol. Run:

touch src/MyERC721.sol

Add the code:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.19;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";

contract MyERC721 is ERC721 {
    uint256 private _nextTokenId;

    constructor() ERC721("MyNFT", "MNFT") {}

    function mint(address to) public {
        uint256 tokenId = _nextTokenId;
        _safeMint(to, tokenId);
        _nextTokenId++;
    }

    function getNextTokenId() public view returns (uint256) {
        return _nextTokenId;
    }
}

This contract:

Inherits from OpenZeppelin’s ERC721 contract
Sets the name to "MyNFT" and symbol "MNFT"
Includes a mint function allowing the creation of NFTs
Tracks the next available token ID

Step 2: Compile the Contract

Compile your contract:

forge build

Step 3: Prepare Signer for Deployment

This tutorial uses the Foundry Keystore for increased security. Create a new keystore:

cast wallet import skale-deployer --private-key $(cast wallet new | grep 'Private key:' | awk '{print $3}')

Provide a password to encrypt the keystore file when running the command. If you forget the password, it cannot be recovered.

Get your wallet address:

cast wallet address --account skale-deployer

Visit the sFUEL Station, toggle testnet, and fill up on sFUEL.

Make sure testnet mode is enabled on the sFUEL Station if you’re using a testnet SKALE Chain!

Step 4: Deploy the Contract

Deploy your ERC-721 contract:

forge create src/MyERC721.sol:MyERC721 \
    --account skale-deployer \
    --rpc-url skale_testnet \
    --broadcast \
    --legacy

The --legacy flag is required for SKALE Chains. For more information, see Troubleshooting.

Example deployment output:

Enter keystore password:
Deployer: 0x63a38D694de837dDF765f9b2704814275586D812
Deployed to: 0x4A435f6E471f773173774E860EBDcd17B132a2b4
Transaction hash: 0x3f6cc66e860cb82a6a62e3f5181c401e5558d60d622a9157437002e16c1ce488

Step 5: Verify Your Smart Contract

Verify the contract on the block explorer:

forge verify-contract \
    --rpc-url skale_testnet \
    <DEPLOYED_ADDRESS> \
    src/MyERC721.sol:MyERC721 \
    --verifier blockscout \
    --verifier-url https://base-sepolia-testnet-explorer.skalenodes.com/api

Replace <DEPLOYED_ADDRESS> with your smart contract address.

Step 0: Setup Hardhat

If your Hardhat project isn’t set up yet, please go to the Hardhat setup section before proceeding.

Step 1: Create the ERC-721 Contract

Create a contract script in contracts/MyERC721.sol. Run:

touch contracts/MyERC721.sol

Add the code:

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.19;

import "@openzeppelin/contracts/token/ERC721/ERC721.sol";

contract MyERC721 is ERC721 {
    uint256 private _nextTokenId;

    constructor() ERC721("MyNFT", "MNFT") {}

    function mint(address to) public {
        uint256 tokenId = _nextTokenId;
        _safeMint(to, tokenId);
        _nextTokenId++;
    }
}

Step 2: Compile Contracts

npx hardhat compile

Step 3: Create a Deployment Script

Create the deployemnt script in scripts/deploy_erc721.js. Run:

touch scripts/deploy_erc721.js

Add the deployment code:

const hre = require("hardhat");

async function main() {
    const NFT = await hre.ethers.getContractFactory("MyERC721");
    const nft = await NFT.deploy();

    await nft.waitForDeployment();

    console.log("Contract deployed to:", await nft.getAddress());
}

main().catch((error) => {
    console.error(error);
    process.exit(1);
});

Step 4: Run Tests

npx hardhat test

Step 5: Deploy to SKALE

npx hardhat run scripts/deploy_erc721.js --network skale_testnet

SKALE-Specific Considerations

Transaction Type: Hardhat generally handles transaction types automatically, but confirm your version supports legacy transactions if needed.
Gas Configuration:
SKALE has zero gas fees, but still requires sFUEL for transactions.

networks: {
    skale_testnet: {
        url: "...",
        accounts: [...],
        gasPrice: 0, // SKALE has zero gas fees
    },
},

Contract Verification:

npx hardhat verify --network skale_testnet <CONTRACT_ADDRESS> <CONSTRUCTOR_ARGS>

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Deploy an ERC-721 Token