Connect and sign

You can connect to MetaMask and sign data in a single interaction from your JavaScript, iOS, Android, or Unity dapp using MetaMask SDK.

The SDK's connectAndSign method provides a streamlined approach for dapps to interact with MetaMask. This method combines the eth_requestAccounts and personal_sign RPC methods, executing them sequentially. connectAndSign takes one parameter, the message string to be signed, and passes the message and the output of eth_requestAccounts directly to personal_sign.

This method enhances dapp user experience, especially on mobile platforms, by allowing users to connect to MetaMask and sign a message in a single interaction, requiring only one switch between the mobile dapp and MetaMask Mobile. This is useful for various purposes such as authentication and transaction verification.

The following instructions describe how to connect and sign in JavaScript. You can also see the Unity instructions.

Prerequisites

• MetaMask SDK set up in your JavaScript dapp.

• MetaMask Mobile version 7.10 or later. Your users must have an updated version of MetaMask Mobile for this feature to work correctly. For older versions of MetaMask, this function may not work as expected.

Use the connectAndSign method

Use the connectAndSign method as follows:

const connectAndSign = async () => {
  try {
    const signResult = await sdk?.connectAndSign({
      msg: "Connect + Sign message",
    });
    setResponse(signResult);
  } catch (err) {
    console.warn("failed to connect..", err);
  }
};

To invoke connectAndSign:

1. Ensure the MetaMaskSDK instance (sdk in this context) is properly initialized and available.
2. Call connectAndSign with the message to be signed.
3. Handle the promise to process the response or catch any errors.

Examples

The following is an example of using the connectAndSign method in a React dapp, integrating it into a functional component:

import React, { useState } from "react";
import { useSDK } from "@metamask/sdk-react";

function MyComponent() {
  const { sdk } = useSDK();
  const [signedMessage, setSignedMessage] = useState("");

  const handleConnectAndSign = async () => {
    try {
      const message = "Your message here";
      const signature = await sdk.connectAndSign({ msg: message });
      setSignedMessage(signature);
    } catch (error) {
      console.error("Error in signing:", error);
    }
  };

  return (
    <div>
      <button onClick={handleConnectAndSign}>Connect and Sign</button>
      {signedMessage && <p>Signed Message: {signedMessage}</p>}
    </div>
  );
}

For a comprehensive React example, see the App.tsx file of the example React dapp.

For examples of using the connectAndSign function in Next.js and Vue.js, see the example Next.js dapp and example Vue.js dapp in the JavaScript SDK GitHub repository.