MetaMask is a web extension that allows you to manage your Ethereum private keys via your web browser. By doing so, it serves as a wallet for Ether and ERC20 tokens, and allows you to visit the distributed web of tomorrow in your browser today. To be more specific, it allows you to run Ethereum Dapps (Decentralized Apps) right in your browser without running a full Ethereum node. (In other words, you don't have to download and sync the full blockchain on your device or computer). Our mission is to make Ethereum as easy to use for as many people as possible.