Metamask

MetaMask is a non-custodial software wallet, meaning the private keys and seed phrase that control the funds stay encrypted on the user's own device rather than on a company server. Built by developers Aaron Davis and Dan Finlay at ConsenSys and released in 2016, it started as an Ethereum-only browser extension and has since grown into one of the most widely used self-custody wallets in crypto, with a companion mobile app added in 2020.

Technically, MetaMask works by injecting a Web3 provider into the browser, which lets any website request a connection, read a public address, and prompt the user to approve or sign a transaction. This "connect wallet" pattern is the standard way people log into decentralized exchanges, NFT marketplaces, and lending protocols without handing over custody of their assets. Support for ERC-20 tokens arrived in 2017, and coverage later expanded to other EVM-compatible networks such as BNB Chain, Polygon, and Arbitrum, plus native, non-custodial support for Bitcoin and Solana added through MetaMask's Snaps plugin system.

Because it holds no funds itself, MetaMask carries the same trade-offs as any self-custody tool:

• Losing the seed phrase means permanently losing access to the wallet.
• Phishing sites and malicious smart contract approvals are a common attack vector, since a signed approval can grant a scam contract spending rights over tokens.
• Larger balances are often paired with a hardware wallet for offline key storage.

Despite these risks, MetaMask remains a default entry point into Ethereum and broader Web3 activity, and it now also offers built-in swaps, bridging, and a debit-style card for spending crypto directly.