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Connect to MetaMask using JavaScript

Get started with MetaMask SDK in your JavaScript dapp.

Prerequisites​

  • Node.js version 19 or later installed.
  • A package manager installed, such as npm, Yarn, pnpm, or bun.
  • MetaMask installed in your browser or on mobile.

Steps​

1. Install the SDK​

Install the SDK in an existing JavaScript project:

npm install @metamask/sdk

2. Initialize the SDK​

The following are examples of using the SDK in various JavaScript environments:

import { MetaMaskSDK } from "@metamask/sdk"

const MMSDK = new MetaMaskSDK({
  dappMetadata: {
    name: "Example JavaScript dapp",
    url: window.location.href,
    // iconUrl: "https://mydapp.com/icon.png" // Optional
  },
  infuraAPIKey: process.env.INFURA_API_KEY,
})

These examples configure the SDK with the following options:

  • dappMetadata - Ensures trust by showing your dapp's name, url, and iconUrl during connection.

  • infuraAPIKey - Enables read-only RPC and load‑balancing.

3. Connect and use provider​

Connect to MetaMask and get the provider for RPC requests:

const provider = MMSDK.getProvider()

const accounts = await MMSDK.connect()
console.log("Connected account:", accounts[0])

const result = await provider.request({
  method: "eth_accounts",
  params: [],
})
console.log("eth_accounts result:", result)

MMSDK.connect() handles cross-platform connection (desktop and mobile), including deeplinking.

Use provider.request() for arbitrary JSON-RPC requests like eth_chainId or eth_getBalance, or for batching requests via metamask_batch.

Common SDK methods at a glance​

MethodDescription
connect()Triggers wallet connection flow
connectAndSign({ msg: '...' })Connects and prompts user to sign a message
getProvider()Returns the provider object for RPC requests
provider.request({ method, params })Calls any Ethereum JSON‑RPC method
Batched RPCUse metamask_batch to group multiple JSON-RPC requests

Usage example​

// 1. Connect and get accounts
const accounts = await MMSDK.connect()

// 2. Connect and sign in one step
const signResult = await MMSDK.connectAndSign({
  msg: "Sign in to Dapp",
})

// 3. Get provider for RPC requests
const provider = MMSDK.getProvider()

// 4. Make an RPC request
const result = await provider.request({
  method: "eth_accounts",
  params: [],
})

// 5. Batch multiple RPC requests
const batchResults = await provider.request({
  method: "metamask_batch",
  params: [
    { method: "eth_accounts" },
    { method: "eth_chainId" }
  ]
})
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