Run a development network

You can run a personal Ethereum development network using Hardhat, which allows you to develop a dapp in a secure test environment.

note

When using a local development blockchain such as Hardhat Network or anvil, your node must calculate gas to make transactions on MetaMask.

Connect to Hardhat Network

Follow these steps to connect MetaMask to Hardhat Network.

1. Set up a Hardhat project.

2. Create a new MetaMask seed phrase specifically for development.

   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 with a hardhat network. In this networks.hardhat configuration:

   • Specify your MetaMask seed phrase in the accounts.mnemonic field.

     tip

     Alternatively, to prevent committing your seed phrase, we recommend adding your seed phrase to a .env file and using the process.env global variable in hardhat.config.js.

   • Specify the chain ID 1337 in the chainId field.

   For example:

   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 configuration), which makes it easy to start development.

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

5. You can now 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 in the interactive API playground.

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

Once you have your development environment set up and development network running, you can connect your dapp to MetaMask by setting up MetaMask SDK, detecting MetaMask, detecting a user's network, and accessing a user's accounts.

For an end-to-end example, you can also follow the Create a simple React dapp tutorial.