How to stop someone submitting a Google Form twice

Use 'Limit to 1 response', which works but forces every respondent to sign in to a Google account. Without a sign-in there is no reliable way to identify a person in a browser; personal links or a self-reported email are the practical alternatives.

Last reviewed 1 September 2026

Google Forms has a Limit to 1 response setting. It works, but it has one consequence people rarely expect: it forces every respondent to sign in to a Google account, because that account is how Google recognises them.

The built-in way

Open the form, then Settings → Responses.
Turn on Limit to 1 response.

Anyone without a Google account, or signed in to the wrong one, cannot submit at all. For a school with managed accounts that is fine. For a public survey it will quietly cost you responses, and you will not see the ones you lost.

When you cannot require a sign-in

Without an account there is no perfect answer, because there is nothing that reliably identifies a person in a browser. The practical options, strongest first:

Personal links. Send each person their own link and allow one submission per link. Someone can forward theirs, but they lose their own attempt by doing it.
Ask for an email on the way in and count submissions against it. Self-reported, so it identifies cooperative people rather than authenticating anyone.
A browser cookie. Stops the accidental double-submit. Cleared site data or a private window defeats it.

Be honest with yourself about which problem you have. Stopping an accident — someone pressing submit twice — is easy. Stopping a determined second attempt needs real identity, and the only identity Google Forms can verify is a Google account.

What does not work

Checking IP addresses looks appealing and fails badly: a whole school shares one address, so you would block classmates, while phones on mobile data get a fresh address each time.

AI Forms for Google Docs does this from your phone — no add-on, no laptop. Get it on the App Store.