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Hardhat 3

Using Configuration Variables

In the previous section, you added your private key and RPC URL (which contains an API key) directly to the config file. This isn’t a good practice because it can expose sensitive information. To avoid this, Hardhat supports Configuration Variables.

Update the sepolia network configuration in your hardhat.config.ts like this:

hardhat.config.ts
import hardhatToolboxViemPlugin from "@nomicfoundation/hardhat-toolbox-viem";
import { defineConfig } from "hardhat/config";
import { configVariable, defineConfig } from "hardhat/config";


export default defineConfig({
  plugins: [hardhatToolboxViemPlugin],
  solidity: {
    version: "0.8.28",
  },
  networks: {
    sepolia: {
      type: "http",
      url: "<SEPOLIA_RPC_URL>",
      accounts: ["<SEPOLIA_PRIVATE_KEY>"],
      url: configVariable("SEPOLIA_RPC_URL"),
      accounts: [configVariable("SEPOLIA_PRIVATE_KEY")],
    },
  },
});

This uses configVariable to create Configuration Variables named SEPOLIA_RPC_URL and SEPOLIA_PRIVATE_KEY and use them in your config. Hardhat includes a plugin to securely store and retrieve these values in a local keystore.

Using hardhat-keystore

Section titled “Using hardhat-keystore”

Add these variables to the keystore by running the following command:

Terminal window
npx hardhat keystore set SEPOLIA_RPC_URL

You’ll be prompted to enter the keystore password (or set one if this is your first time) and then enter the variable value. Paste your Sepolia RPC URL as the value.

Run the command again to add the private key:

Terminal window
npx hardhat keystore set SEPOLIA_PRIVATE_KEY

After adding both variables, run the deployment command again:

Terminal window
npx hardhat ignition deploy ignition/modules/Counter.ts --network sepolia

This time, you’ll need to enter the keystore password to retrieve the Configuration Variable values, but you won’t need to put any sensitive information in your config file.

Since you’ve already deployed the contract, you’ll see that nothing new needs to be deployed.