# Run a Development Network - MetaMask Connect

> Set up and connect MetaMask to a Hardhat development network for local EVM testing with gas calculation and custom chain configuration.

# Run a development network

Run a personal Ethereum development network using [Hardhat](https://hardhat.org/hardhat-network/docs/overview#hardhat-network)
to develop a dapp in a secure test environment.

:::note
When using a local development blockchain such as Hardhat Network or
[anvil](https://book.getfoundry.sh/anvil/#overview-of-anvil), your node must calculate gas to make
transactions on MetaMask.
:::

## Connect to Hardhat

Follow these steps to connect MetaMask to Hardhat Network.

1. [Set up a Hardhat project.](https://hardhat.org/hardhat-runner/docs/guides/project-setup)

2. Create a new
   [MetaMask seed phrase](https://support.metamask.io/privacy-and-security/what-is-a-secret-recovery-phrase-and-how-to-keep-your-crypto-wallet-secure/)
   specifically for development.

   :::caution important
   Your seed phrase controls all your accounts, so we recommend keeping at least one seed phrase for
   development, separate from any used to store real value.
   You can manage multiple seed phrases by using multiple browser profiles, each with its own
   MetaMask installation.
   :::

3. In your `hardhat.config.js` file, specify a
   [`networks` configuration](https://hardhat.org/hardhat-runner/docs/config#networks-configuration)
   with a `hardhat` network.
   In this `networks.hardhat` configuration:
   - Specify your MetaMask seed phrase in the
     [`accounts.mnemonic`](https://hardhat.org/hardhat-network/docs/reference#accounts) field.

     :::tip
     Alternatively, to prevent committing your seed phrase, we recommend adding your seed phrase to a
     [`.env` file](/services/how-to/javascript-dotenv) and using the
     `process.env` global variable in `hardhat.config.js`.
     :::

   - Specify the [chain ID `1337`](https://hardhat.org/hardhat-network/docs/metamask-issue) in the
     [`chainId`](https://hardhat.org/hardhat-network/docs/reference#chainid) field.

   For example:

   ```js title="hardhat.config.js"
   module.exports = {
     networks: {
       hardhat: {
         accounts: {
           mnemonic: process.env.SEED_PHRASE,
         },
         chainId: 1337,
       },
     },
   }
   ```

   Hardhat automatically gives each of your first 20 accounts 10000 test ether (you can modify
   these numbers in the [`accounts`](https://hardhat.org/hardhat-network/docs/reference#accounts)
   configuration), to quickly start development.

4. Run `npx hardhat node` to run Hardhat Network and expose a JSON-RPC interface.

5. Connect MetaMask to your Hardhat Network RPC URL, `http://127.0.0.1:8545/`.
   In the MetaMask extension:
   1. In the upper left corner, select the network you're currently connected to.

   2. Select **Add network**.

   3. Select **Add a network manually**.

   4. Enter your Hardhat Network RPC URL, `http://127.0.0.1:8545/` (or `http://localhost:8545`).

   5. Enter your Hardhat Network chain ID, `1337` (or `0x539` in hexadecimal format).

   :::tip
   Alternatively, you can add Hardhat Network to MetaMask using
   [`wallet_addEthereumChain`](../../reference/json-rpc-api/index.md).
   :::

## Reset your local nonce calculation

If you restart your development network, you can accidentally confuse MetaMask
because it calculates the next nonce based on both the
network state _and_ the known sent transactions.

To clear MetaMask's transaction queue and reset its nonce calculation, go to **Settings > Advanced**
and select **Reset account**.

## Next steps

- [Manage networks](../manage-networks.md)
- [Send transactions](../send-transactions/index.md)
- [Production readiness checklist](./production-readiness.md)