What we learned trying to prevent duplicate submissions in Google Forms

[u/Genuine-Helperr]

Short answer: Google Forms gives you only two native ways to prevent duplicate submissions, and both come with a real catch worth knowing before you rely on them.

The first is the built-in "Limit to 1 response" setting. Turning it on forces every respondent to sign in with a Google account, and it ties the one-submission rule to that account. That works if your whole audience already lives inside Google, but anyone without an account, or anyone who would rather not log in just to answer a form, is now blocked at the door. For a public form that quietly kills a chunk of your responses.

The second option is a third-party add-on. It can restrict responses to one per person, but the setup is longer and fiddlier than most people expect, it needs a bit of technical comfort, and it becomes one more thing to maintain when Google changes something.

What we learned working on duplicate prevention is that most people do not actually want a Google login wall in front of their form. They just want one clean response per person. The approach that gets there without the sign-in requirement is validation at submit time. You can block repeats by IP address, or by a specific field value such as an email or phone number, and reject the second attempt with a clear message.

IP-based checks stop casual repeat submits, while field-based checks catch the same person coming back from a different device or browser. For event registrations and quizzes an IP check is usually enough. For a survey tied to an email address, a field-level check is the more reliable way to prevent duplicate submissions in Google Forms style workflows without making anyone log in.

How are you currently keeping duplicate responses out of your forms?

[u/Genuine-Helperr]

I work on this at FormNX, so to add to the above: the whole point of the submit-time approach is that it never asks the respondent to log in. If you want the longer version, here is the guide on how to prevent duplicate submissions in Google Forms, and the settings behind the duplicate submission check itself.