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Multichain quickstart

Get started with MetaMask Connect Multichain in your JavaScript (Vite) dapp.

Prerequisites​

note

This quickstart uses Vite as the build tool for convenience, but MetaMask Connect Multichain works with vanilla JavaScript or any build tool of your choice.

Steps​

1. Install MetaMask Connect Multichain​

Install the multichain client in an existing JavaScript (Vite) project:

npm install @metamask/connect-multichain

2. Initialize MetaMask Connect Multichain​

The following is an example of using MetaMask Connect Multichain for a multichain dapp in a JavaScript (Vite) project:

import { createMultichainClient } from '@metamask/connect-multichain'

const client = await createMultichainClient({
  dapp: {
    name: 'My Multichain Dapp',
    url: window.location.href,
    iconUrl: 'https://mydapp.com/icon.png',
  },
  api: {
    supportedNetworks: {
      'eip155:1': 'https://mainnet.infura.io/v3/YOUR_INFURA_API_KEY',
      'eip155:137': 'https://polygon-mainnet.infura.io/v3/YOUR_INFURA_API_KEY',
      'solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp':
        'https://solana-mainnet.infura.io/v3/YOUR_INFURA_API_KEY',
    },
  },
})

This example configures MetaMask Connect Multichain with the following options:

  • dapp - Ensures trust by showing your dapp's name, url, and iconUrl during connection.
  • api.supportedNetworks - A map of CAIP-2 chain IDs to RPC URLs for all networks supported by the dapp.

3. Connect and use the Multichain client​

Connect to MetaMask, get accounts from the session, and invoke RPC methods on chain of your choice:

await client.connect(['eip155:1', 'eip155:137', 'solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp'], [])

const session = await client.getSession()
const ethAccounts = session.sessionScopes['eip155:1']?.accounts || []
const solAccounts = session.sessionScopes['solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp']?.accounts || []
console.log('ETH accounts:', ethAccounts)
console.log('SOL accounts:', solAccounts)

if (ethAccounts.length > 0) {
  const ethAddress = ethAccounts[0].split(':')[2]
  const ethBalance = await client.invokeMethod({
    scope: 'eip155:1', // Ethereum Mainnet
    request: {
      method: 'eth_getBalance',
      params: [ethAddress, 'latest'],
    },
  })
  console.log('ETH balance:', ethBalance)
}

The user sees a single approval prompt for all requested chains. Use invokeMethod() to call RPC methods on any chain in the session by specifying a scope.

Multichain client methods at a glance​

MethodDescription
connect(scopes, caipAccountIds)Connects to MetaMask with multichain scopes
getSession()Returns the current session with approved accounts
invokeMethod({ scope, request })Calls an RPC method on a specific chain using a scope
disconnect()Disconnects all scopes and ends the session
disconnect(scopes)Disconnects specific scopes without ending the session
on(event, handler)Registers an event handler
off(event, handler)Removes an event handler
getInfuraRpcUrls({ infuraApiKey })Generates Infura RPC URLs keyed by CAIP-2 chain ID

Next steps​

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