#7. Deploying to a live network

Once you're ready to share your dApp with other people, you may want to deploy it to a live network. This way others can access an instance that's not running locally on your system.

The "mainnet" Ethereum network deals with real money, but there are separate "testnet" networks that do not. These testnets provide shared staging environments that do a good job of mimicking the real world scenario without putting real money at stake, and Ethereum has several, like Sepolia and Goerli. We recommend you deploy your contracts to the Sepolia testnet.

At the software level, deploying to a testnet is the same as deploying to mainnet. The only difference is which network you connect to. Let's look into what the code to deploy your contracts using Hardhat Ignition would look like.

In Hardhat Ignition, deployments are defined through Ignition Modules. These modules serve as abstractions, helping you outline and describe the system that you want to deploy. Each Ignition Module encapsulates a group of smart contract instances and operations within your system.

You can think of Ignition Modules as being conceptually similar to JavaScript modules. In JavaScript, you create a module to group definitions of functions, classes, and values, and then you export some of them. In Hardhat Ignition, you create a module where you group definitions of smart contract instances and operations, and you export some of those contracts.

Let's create a new directory ignition inside the project root's directory, then, create a directory named modules inside of the ignition directory. Paste the following into a TokenModule.js file in that directory:

const { buildModule } = require("@nomicfoundation/hardhat-toolbox");

const TokenModule = buildModule("TokenModule", (m) => {
  const token = m.contract("Token");

  return { token };
});

module.exports = TokenModule;

To tell Hardhat to connect to a specific Ethereum network, you can use the --network parameter when running any task, like this:

npx hardhat ignition deploy ./ignition/modules/TokenModule.js --network <network-name>

With our current configuration, running it without the --network parameter would cause the code to run against an embedded instance of Hardhat Network. In this scenario, the deployment actually gets lost when Hardhat finishes running, but it's still useful to test that our deployment code works:

$ npx hardhat ignition deploy ./ignition/modules/TokenModule.js
Compiled 1 Solidity file successfully (evm target: paris).
You are running Hardhat Ignition against an in-process instance of Hardhat Network.
This will execute the deployment, but the results will be lost.
You can use --network <network-name> to deploy to a different network.

Hardhat Ignition 🚀

Deploying [ TokenModule ]

Batch #1
  Executed TokenModule#Token

[ TokenModule ] successfully deployed 🚀

Deployed Addresses

TokenModule#Token - 0x5FbDB2315678afecb367f032d93F642f64180aa3

# Deploying to remote networks

To deploy to a remote network such as mainnet or any testnet, you need to add a network entry to your hardhat.config.js file. We’ll use Sepolia for this example, but you can add any network similarly:

require("@nomicfoundation/hardhat-toolbox");

// Go to https://infura.io, sign up, create a new API key
// in its dashboard, and replace "KEY" with it
const INFURA_API_KEY = "KEY";

// Replace this private key with your Sepolia account private key
// To export your private key from Coinbase Wallet, go to
// Settings > Developer Settings > Show private key
// To export your private key from Metamask, open Metamask and
// go to Account Details > Export Private Key
// Beware: NEVER put real Ether into testing accounts
const SEPOLIA_PRIVATE_KEY = "YOUR SEPOLIA PRIVATE KEY";

module.exports = {
  solidity: "0.8.19",
  networks: {
    sepolia: {
      url: `https://sepolia.infura.io/v3/${INFURA_API_KEY}`,
      accounts: [SEPOLIA_PRIVATE_KEY]
    }
  }
};

require("@nomicfoundation/hardhat-toolbox");

// Go to https://alchemy.com, sign up, create a new App in
// its dashboard, and replace "KEY" with its key
const ALCHEMY_API_KEY = "KEY";

// Replace this private key with your Sepolia account private key
// To export your private key from Coinbase Wallet, go to
// Settings > Developer Settings > Show private key
// To export your private key from Metamask, open Metamask and
// go to Account Details > Export Private Key
// Beware: NEVER put real Ether into testing accounts
const SEPOLIA_PRIVATE_KEY = "YOUR SEPOLIA PRIVATE KEY";

module.exports = {
  solidity: "0.8.19",
  networks: {
    sepolia: {
      url: `https://eth-sepolia.g.alchemy.com/v2/${ALCHEMY_API_KEY}`,
      accounts: [SEPOLIA_PRIVATE_KEY]
    }
  }
};

We're using Infura or Alchemy, but pointing url to any Ethereum node or gateway. Go grab your API key and come back.

To deploy on Sepolia you need to send some Sepolia ether to the address that's going to be making the deployment. You can get testnet ether from a faucet, a service that distributes testing-ETH for free. Here are a few for Sepolia:

• Alchemy Sepolia Faucet
• Coinbase Sepolia Faucet (only works if you are using the Coinbase Wallet)
• Infura Sepolia Faucet
• Chainstack Sepolia Faucet

You'll have to change your wallet's network to Sepolia before transacting.

Finally, run:

npx hardhat ignition deploy ./ignition/modules/TokenModule.js --network sepolia

If everything went well, you should see the deployed contract address.