Sign in with Ethereum

You can set up Sign-In with Ethereum (SIWE) to enable users to easily sign in to your dapp by authenticating with their MetaMask wallet.

MetaMask supports the SIWE standard message format as specified in ERC-4361. When your dapp prompts a user to sign a message that follows the SIWE format, MetaMask parses the message and gives the user a friendly interface prompting them to sign in to your dapp:

Domain binding

MetaMask supports domain binding with SIWE to help prevent phishing attacks. When a site asks a user to sign a SIWE message, but the domain in the message doesn't match the site the user is on, MetaMask displays a warning in the sign-in interface. The user must explicitly select to proceed, accepting the risk of a phishing attack.

important

MetaMask displays a prominent warning for mismatched domains, but does not block users from bypassing the warning and accepting the sign-in request. This is to not break existing dapps that may have use cases for mismatched domains.

Example

The following is an example of setting up SIWE with MetaMask using personal_sign:

index.js

const siweSign = async (siweMessage) => {
  try {
    const from = accounts[0];
    const msg = `0x${Buffer.from(siweMessage, "utf8").toString("hex")}`;
    const sign = await provider // Or window.ethereum if you don't support EIP-6963.
      .request({
        method: "personal_sign",
        params: [msg, from],
      });
    siweResult.innerHTML = sign;
  } catch (err) {
    console.error(err);
    siweResult.innerHTML = `Error: ${err.message}`;
  }
};

siwe.onclick = async () => {
  const domain = window.location.host;
  const from = accounts[0];
  const siweMessage = `${domain} wants you to sign in with your Ethereum account:\n${from}\n\nI accept the MetaMask Terms of Service: https://community.metamask.io/tos\n\nURI: https://${domain}\nVersion: 1\nChain ID: 1\nNonce: 32891757\nIssued At: 2021-09-30T16:25:24.000Z`;
  siweSign(siweMessage);
};

The following HTML displays the SIWE button:

index.html

<h4>Sign-In with Ethereum</h4>
<button type="button" id="siwe">Sign-In with Ethereum</button>
<p class="alert">Result:<span id="siweResult"></span></p>

See the live example and test dapp source code for more information.