The MetaMask browser extension turns Google Chrome into an Ethereum browser, letting websites retrieve data from the blockchain, and letting users securely manage identities and sign transactions.
Your account vault is encrypted and locally stored within your browser, meaning no account information ever touches our servers. However, with your secret phrase, you can easily restore your vault with the same accounts.
At first glance, Metamask enables you to send ether like a normal wallet application, but Metamask's true strength lies in enabling your browser to visit Ethereum enabled websites.
When you visit a Dapp like Tokens with MetaMask installed, that website has access to the Ethereum blockchain via the standard Web3 Javascript API. When it wants to write to the blockchain, it asks web3 to send the transaction, prompting MetaMask to ask for user confirmation.
Now I have my own MetaMaskCoins! I can check my balance or, if I want to send some to another account, I can click the copy link on it. I check its balance, see it has none, then send it some meta-coins!
This has been nice, but it’s all been on the test-net. I can always switch what blockchain I’m working on, say the main blockhain, and I’m ready issue a token with the full security of the Ethereum blockchain.
MetaMask connects to these blockchains with no synchronization time because we host blockchain nodes by default. You can always point MetaMask at your own Ethereum RPC Server, and fully control your connection to the blockchain.
And that’s how MetaMask lets ordinary websites talk to a trusted Ethereum provider, all while letting the user store and manage their own private keys. We hope this will help enable a new wave of blockchain-enabled websites.