Crypto glossary
Browser extension wallet
A browser extension wallet lives inside Chrome, Firefox or Brave, stores encrypted keys locally and injects a provider so websites can request signatures.
Extension wallets such as MetaMask, Phantom or Rabby install like any browser add-on. They keep the user's keys encrypted on the computer, unlocked with a password, and expose an interface that websites can call. When a dApp asks for a transaction or message signature, the extension opens a pop-up showing what is being requested, and nothing happens until the user approves.
This model made DeFi and NFTs usable on the desktop: one click on connect wallet, and the site can read the address and propose actions. Most onchain activity on Ethereum-compatible chains and Solana still passes through such extensions, often paired with a hardware wallet that does the actual signing.
The browser is a hostile place. Fake extensions with copied logos show up in web stores, malicious sites push approvals or signatures that hand over tokens, and other extensions or infostealers on the same machine can target the wallet's files. Use a dedicated browser profile, install only from the official link, read every pop-up, and pair the extension with a hardware device for significant funds.
Example
A user searching for a wallet extension clicks a sponsored result, installs a lookalike add-on and imports her seed phrase into it; the attackers empty her accounts within the hour.