How to prevent more than one submission?

Repeated submissions can distort a survey when the same person sends the form several times from the same device. In Porsline’s online survey builder, One Submission per Device gives you a simple way to limit repeat submissions from the same browser.

This video also explains when it is better to flag possible duplicates for review instead of blocking them, and when you need stronger respondent-level control.

What You Will Learn About Duplicate Responses

• Activate One Submission per Device to block another submission from the same browser.
• Recognise the message respondents see after an attempted repeat submission.
• Use Flag as Spam when you prefer to keep responses but identify possible duplicates.
• Review flagged responses later in the Results Table.
• Understand why browser-based restrictions cannot guarantee one response per person.
• Choose Respondent Authentication when stricter access control is required.

The distinction is important: One Submission per Device controls repeated activity from a browser or device. It does not establish a respondent’s identity.

Where Duplicate-Response Controls Are Useful

Reduce Repeat Entries in Open Research Surveys

A research team sharing a general survey link may want to reduce the chance that the same device contributes several responses. In market research surveys, One Submission per Device can provide a practical first layer of duplicate control, while Flag as Spam lets researchers inspect possible repeated entries rather than excluding them automatically.

This is most appropriate when the survey does not require verified individual access.

Protect a Defined Academic Study Sample

An academic researcher may work with a predefined participant group where each person should contribute only one response. For academic research surveys, a device-based restriction may not be sufficient because a participant can change browsers or devices.

When participation must be tied more strictly to an approved individual, Respondent Authentication can use a Code, SMS OTP or Email instead.

Before publishing your survey, decide whether you need to discourage repeated submissions, identify them for review or enforce access for a predefined group. Test the chosen setting from the respondent side, including a second submission attempt, before distributing the real survey.