What is MetaMask?

MetaMask is a crypto wallet used to manage blockchain accounts and connect to apps. It is available as a browser extension and mobile app. Assets do not sit inside the application like files: balances and transfer records belong to the relevant blockchain. The wallet provides an interface for account access and transaction authorization.

An app connection can specify which accounts and networks are shared. Ordinary connection permission is different from authority to spend tokens. Additional permissions can change what the app is allowed to do.

Example

Imagine Alex has two accounts in MetaMask. To view a portfolio, Alex connects only the first account to a website. The site can read that address’s on-chain balance; selecting it does not also share the second account. No tokens have been transferred at that point. If the site later requests spending authority, Alex must assess the scope of the new request separately.

Our separate review examines how those account, network and cost controls work in the product.

Definition sources: MetaMask’s getting-started documentation and its app-connection explanation.