If you have ever clicked "Connect Wallet" on a site and then seen a popup asking you to "sign in" rather than approve a transaction, you have used Sign-In with Ethereum. It is a standard way for websites to confirm that you control a wallet address, without asking for an email, a password, or any personal data.
This article explains what Sign-In with Ethereum actually does, how it differs from a normal transaction or a token approval, and what to check before you sign one of these messages.
What Sign-In with Ethereum is
Sign-In with Ethereum is defined by a standard called EIP-4361 (also written as ERC-4361). It describes a plain text message format that a website can ask your wallet to sign to prove you hold a given address.
The message usually includes:
- The domain making the request (for example,
app.example.com) - Your wallet address
- A short statement describing what you are agreeing to
- The chain ID, so the message is tied to a specific network
- A random, one time value called a nonce
- An issued-at timestamp, and sometimes an expiration time
Your wallet shows you this text, and if you approve, it produces a signature using your private key. That signature proves you control the address without ever exposing the key itself.
How it differs from other prompts
Wallets ask you to approve a few different kinds of requests, and it helps to know which one you are looking at.
Transactions move funds or call a smart contract function. They cost gas and change something on chain, whether that is your balance, an approval, or a contract's state.
Token approvals are a specific type of transaction that gives a contract permission to move tokens from your wallet later. If you want a refresher on how these work and how to check what you have approved, see our guide on token approvals and checking and revoking approvals.
Typed data signatures, covered in our EIP-712 article, are structured, human readable signatures often used for things like gasless approvals or off chain orders.
Sign-In with Ethereum messages are plain text signatures with no on chain effect at all. Signing one does not move any tokens, does not cost gas, and does not grant any contract permission. It is closer to typing a password into a login box than to authorizing a payment.
Because a SIWE signature has no on chain effect by itself, it is generally lower risk than approving a transaction. But "lower risk" is not "no risk," which is why the details in the message still matter.
What to actually check before signing
Even though signing a SIWE message will not move your funds, it is worth reading the prompt rather than clicking through it. A few things are worth a second look.
The domain. The message should name the exact site you are trying to log into. If you are on app.realsite.com but the signature request shows a different domain, or no domain at all, stop and close the popup. A mismatched domain is one of the more reliable signs of a phishing attempt, since the whole point of including the domain in the message is to stop a signature obtained on one site from being replayed on another.
What the message actually says. Your wallet displays the raw text of the request. If it looks like a login statement with a nonce and a domain, that lines up with SIWE. If instead it contains long strings of unreadable hexadecimal data, or language about transferring assets or granting permissions, it is not a simple login message and deserves more scrutiny before you approve anything.
Where the request came from. If a signature prompt appears after clicking a link in an unsolicited email or message rather than from a site you navigated to directly, treat it the same way you would treat any unexpected wallet prompt. Our article on wallet phishing and drainer scams covers this pattern in more detail.
For a broader look at how wallets present different kinds of requests, our guide on wallet signature requests walks through several examples side by side.
Why sites use it
From a website's point of view, Sign-In with Ethereum removes the need to run its own password database, which also removes one common source of account takeovers, namely leaked or reused passwords. From a user's point of view, it means one wallet can serve as your identity across many sites without creating a new account and password everywhere you go.
It also keeps you in control. A site that only uses SIWE for login cannot move your assets just because you signed in, since the login signature and a spending permission are two different kinds of requests that your wallet will always show separately.
The practical takeaway
Sign-In with Ethereum is a convenience feature, not a source of on chain risk by itself. Signing a correctly formed SIWE message will not cost you gas or give a site access to your funds. The habit worth building is the same one that applies to every wallet prompt: read what you are actually signing, confirm the domain matches the site you meant to visit, and treat anything unexpected or unreadable as a reason to pause rather than click through.