# Using Configuration Variables

Description: Hardhat 3 Tutorial - Using Configuration Variables

Note: This document was authored using MDX

  Source: https://github.com/NomicFoundation/hardhat-website/tree/main/src/content/docs/docs/tutorial/configuration-variables.mdx

  Components used in this page:
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    - :::tip: A helpful tip callout block. Supports custom title `:::tip[Title]` and icon `:::tip{icon="name"}` syntax.

import Run from "@hh/Run.astro";

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:

```ts del={3,14-15} ins={4,16-17}
// 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`

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

<Run command="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:

<Run command="hardhat keystore set SEPOLIA_PRIVATE_KEY" />

After adding both variables, run the deployment command again:

<Run command="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.

:::tip
Learn more about Configuration Variables and how to use them effectively in [our guide](/docs/guides/configuration-variables).

For a deeper understanding, read the [Configuration Variables explanation](/docs/explanations/configuration-variables).
:::