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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:

Sign-in with Ethereum request

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.

Sign-in bad domain
Sign-in bad domain pop-up

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.