# Introduction

Welcome to MetaMask’s Developer Documentation. This documentation is for learning to develop applications for MetaMask.

Breaking Provider Changes

We are in the process of shipping changes that will break some Ethereum web applications. These changes have already shipped for the MetaMask browser extension, and may ship for MetaMask Mobile at any time. Please read our Migration Guide for more details.

Action is required for Ethereum application developers only. MetaMask users do not need to do anything.

# Why MetaMask

MetaMask was created to meet the needs of secure and usable Ethereum-based web sites. In particular, it handles account management and connecting the user to the blockchain.

# Account Management

MetaMask allows users to manage accounts and their keys in a variety of ways, including hardware wallets, while isolating them from the site context. This is a great security improvement over storing the user keys on a single central server, or even in local storage, which can allow for mass account thefts.

This security feature also comes with developer convenience: For developers, you simply interact with the globally available ethereum API that identifies the users of web3-compatible browsers (like MetaMask users), and whenever you request a transaction signature (like eth_sendTransaction, eth_signTypedData, or others), MetaMask will prompt the user in as comprehensible a way as possible. This keeps users informed, and leaves attackers left trying to phish individual users rather than performing mass hacks (although DNS hacks can still be used for phishing en masse).

# Blockchain Connection

MetaMask comes pre-loaded with fast connections to the Ethereum blockchain and several test networks via our friends at Infura. This allows you to get started without synchronizing a full node, while still providing the option to upgrade your security and use the blockchain provider of your choice.

Today, MetaMask is compatible with any blockchain that exposes an Ethereum-compatible JSON RPC API, including custom and private blockchains. For development, we recommend running a test blockchain like Ganache.

We’re aware that there are constantly new private blockchains that people are interested in connecting MetaMask to, and we are building towards easier integration with these many options.

# New Dapp Developers