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title Sign Messages Across Chains - MetaMask Connect Multichain
sidebar_label Sign messages
description Sign messages and typed data on both EVM and Solana chains from a single MetaMask Connect Multichain session using invokeMethod.
keywords
multichain
evm
solana
sign
personal_sign
signTypedData
signMessage
invokeMethod
multichain signing
cross-chain signature

Sign messages on EVM and Solana

This guide shows you how to sign messages and typed data on both EVM networks and Solana from a single multichain session. No network switching is required.

All signing methods route to the MetaMask wallet and require user approval.

Prerequisites

Follow Step 1 of the quickstart to install the multichain client.

Initialize and connect

Initialize a multichain client using createMultichainClient, and connect to both ecosystems using connect:

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

const client = await createMultichainClient({
  dapp: {
    name: 'Multichain Demo',
    url: window.location.href,
  },
  api: {
    supportedNetworks: {
      ...getInfuraRpcUrls({ infuraApiKey: 'YOUR_INFURA_API_KEY' }),
    },
  },
})

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

Sign an EVM message (personal_sign)

Use invokeMethod with personal_sign to sign a plaintext message. The message must be hex-encoded, and the params order is [message, account]:

const message = 'Hello MetaMask!'
const hexMessage =
  '0x' +
  Array.from(new TextEncoder().encode(message))
    .map(b => b.toString(16).padStart(2, '0'))
    .join('')

const signature = await client.invokeMethod({
  scope: 'eip155:1', // Ethereum Mainnet
  request: {
    method: 'personal_sign',
    params: [hexMessage, '0xYourAddress'],
  },
})
console.log('Signature:', signature)

Target a different chain by changing the scope; for example, eip155:137 for Polygon.

Sign EVM typed data (eth_signTypedData_v4)

Use invokeMethod with eth_signTypedData_v4 to sign EIP-712 structured data. The params order is [account, typedDataJSON]. The typed data must be passed as a JSON string, not an object:

const typedData = {
  types: {
    EIP712Domain: [
      { name: 'name', type: 'string' },
      { name: 'version', type: 'string' },
      { name: 'chainId', type: 'uint256' },
      { name: 'verifyingContract', type: 'address' },
    ],
    Mail: [
      { name: 'from', type: 'string' },
      { name: 'to', type: 'string' },
      { name: 'contents', type: 'string' },
    ],
  },
  primaryType: 'Mail',
  domain: {
    name: 'My Dapp',
    version: '1',
    chainId: 1,
    verifyingContract: '0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC',
  },
  message: {
    from: 'Alice',
    to: 'Bob',
    contents: 'Hello!',
  },
}

const signature = await client.invokeMethod({
  scope: 'eip155:1', // Ethereum Mainnet
  request: {
    method: 'eth_signTypedData_v4',
    params: ['0xYourAddress', JSON.stringify(typedData)],
  },
})
console.log('Typed data signature:', signature)

:::note The EIP712Domain type must be declared in types even though primaryType is never EIP712Domain. Chain IDs in the typed data domain.chainId are integers (for example, 1), not hex strings. :::

Sign a Solana message (solana_signMessage)

Use invokeMethod with solana_signMessage to sign an arbitrary message on Solana. The message must be base64-encoded:

const message = btoa('Hello from Solana!')

const result = await client.invokeMethod({
  scope: 'solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp', // Solana Mainnet
  request: {
    method: 'solana_signMessage',
    params: {
      message,
      pubkey: 'YourSolanaPublicKeyBase58',
    },
  },
})
console.log('Signature:', result.signature)

Error handling

Error code Description Action
4001 User rejected the request Show a retry option. Do not treat as an application error.
-32002 Request already pending Wait for the user to respond in MetaMask before retrying. 

try {
  const signature = await client.invokeMethod({
    scope: 'eip155:1',
    request: {
      method: 'personal_sign',
      params: [hexMessage, '0xYourAddress'],
    },
  })
} catch (err) {
  if (err.code === 4001) {
    console.log('User rejected the signature request')
    return
  }
  if (err.code === -32002) {
    console.log('A signing request is already pending')
    return
  }
  throw err
}

Next steps