Integrating MetaMask with your React application is essential for building decentralized applications (dApps) on Ethereum or any EVM-compatible blockchain. In this guide, we’ll walk through:

1. Connecting MetaMask to a React app
2. Retrieving wallet address
3. Sending and signing a transaction using ethers.js

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Prerequisites

Before we start, make sure you have:

• A React application (npx create-react-app my-dapp)
• MetaMask installed in your browser
• ethers.js library installed:

npm install ethers

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1. Detect MetaMask

MetaMask injects an ethereum object into the browser’s window. To check if MetaMask is installed:

if (typeof window.ethereum !== 'undefined') {
  console.log('MetaMask is installed!');
}

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2. Connect to MetaMask

Create a button that connects to MetaMask and retrieves the current user’s address:

import React, { useState } from 'react';

const ConnectWallet = () => {
  const [account, setAccount] = useState(null);

  const connectWallet = async () => {
    if (typeof window.ethereum === 'undefined') {
      alert('Please install MetaMask!');
      return;
    }

    try {
      const accounts = await window.ethereum.request({ method: 'eth_requestAccounts' });
      setAccount(accounts[0]);
    } catch (error) {
      console.error('Connection error:', error);
    }
  };

  return (
    <div>
      <button onClick={connectWallet}>
        {account ? `Connected: ${account}` : 'Connect MetaMask'}
      </button>
    </div>
  );
};

export default ConnectWallet;

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3. Sign and Send a Transaction

Now let’s add the ability to send a small ETH transaction. We’ll use ethers.js for convenience and reliability.

Add ethers.js and setup provider + signer:

import { ethers } from 'ethers';

const sendTransaction = async () => {
  if (!window.ethereum) {
    alert('MetaMask is not available');
    return;
  }

  try {
    // Connect to provider and get signer
    const provider = new ethers.providers.Web3Provider(window.ethereum);
    const signer = provider.getSigner();

    const recipient = '0xAbC123...DEF456'; // Replace with actual address
    const tx = {
      to: recipient,
      value: ethers.utils.parseEther('0.01'), // sending 0.01 ETH
    };

    const txResponse = await signer.sendTransaction(tx);
    console.log('Transaction sent:', txResponse.hash);

    const receipt = await txResponse.wait();
    console.log('Transaction confirmed:', receipt);
  } catch (error) {
    console.error('Transaction failed:', error);
  }
};

Add a Button to Trigger It:

<button onClick={sendTransaction}>Send 0.01 ETH</button>

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Optional: Sign a Message

Instead of sending ETH, you can ask the user to sign a message:

const signMessage = async () => {
  const provider = new ethers.providers.Web3Provider(window.ethereum);
  const signer = provider.getSigner();
  const signature = await signer.signMessage("Sign this to prove you own the wallet.");
  console.log("Signature:", signature);
};

---

Security Tips

• Never expose private keys in frontend code.
• Always validate to addresses before sending ETH.
• Monitor for window.ethereum.on('accountsChanged') to detect wallet changes.

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Final Thoughts

With just a few lines of code, your React app can:

• Detect MetaMask
• Connect to the user’s wallet
• Sign or send transactions using ethers.js

This is a core part of any dApp UX. Once this is in place, you can extend functionality to include ERC-20 token transfers, smart contract interactions, and wallet authentication.

---

Full Component Example

import React, { useState } from 'react';
import { ethers } from 'ethers';

const WalletConnector = () => {
  const [account, setAccount] = useState(null);

  const connectWallet = async () => {
    if (!window.ethereum) {
      alert('Please install MetaMask');
      return;
    }

    const accounts = await window.ethereum.request({ method: 'eth_requestAccounts' });
    setAccount(accounts[0]);
  };

  const sendTransaction = async () => {
    const provider = new ethers.providers.Web3Provider(window.ethereum);
    const signer = provider.getSigner();
    const tx = {
      to: '0xAbC123...DEF456', // replace with valid address
      value: ethers.utils.parseEther('0.01'),
    };
    const txResponse = await signer.sendTransaction(tx);
    console.log('Sent:', txResponse.hash);
    await txResponse.wait();
    console.log('Confirmed');
  };

  return (
    <div>
      <button onClick={connectWallet}>
        {account ? `Connected: ${account}` : 'Connect MetaMask'}
      </button>
      {account && (
        <button onClick={sendTransaction}>Send 0.01 ETH</button>
      )}
    </div>
  );
};

export default WalletConnector;