What is MetaMask?

MetaMask is the most popular Ethereum wallet and Web3 gateway, available as a browser extension (Chrome, Firefox, Brave) and mobile app. It serves as the bridge between web browsers and the Ethereum blockchain. Key functions: (1) Wallet management — stores private keys securely in the browser, generates Ethereum accounts from a 12-word seed phrase; (2) Transaction signing — pops up a confirmation window when a DApp requests a transaction, showing gas fees and transaction details; (3) Web3 provider injection — injects window.ethereum into web pages, allowing DApps to request accounts and send transactions; (4) Network switching — supports Ethereum mainnet, testnets (Goerli, Sepolia), and custom networks (Polygon, BSC, Arbitrum); (5) Token management — displays ETH and ERC-20 token balances; (6) Hardware wallet support — integrates with Ledger and Trezor. DApp connection: const accounts = await window.ethereum.request({ method: "eth_requestAccounts" }). MetaMask has ~30 million monthly active users. Its dominance means most DApps primarily support MetaMask-compatible wallet interfaces.