We recommend always choosing a registered participation type for your surveys to ensure you get more reliable data and to help you build your engagement community. Choosing anonymous as the participation type will remove the registration barrier, but you risk receiving multiple submissions from the same user.
One way to try and resolve this is to use the User ID found in the codified survey report. Anonymous visitors to your site are tracked using cookies, predominantly for reporting purposes such as accurately tracking aware, informed, and engaged visitors.
When an anonymous respondent submits a survey, the cookie in their browser lets us establish a unique user ID in the codified survey report. If you see multiples of the same user ID, it indicates multiple submissions by the same user. You can then manually remove these duplicates from your report.
This method may assist, but you should always use caution when deleting responses based on duplicate user IDs.
This method is not foolproof for the following reasons:
The user ID is only recorded for anonymous submissions, not for unverified users. Unverified users must provide a screen name and email address before submissions, so duplicates are still possible with unverified participation.
As cookies are browser-based, if the same participant visits from different browsers or devices, they will appear in your report under different user IDs. Visitors can also delete their cookies; if they respond again after doing so, they will have a different user ID.
People can share computers and browsers, such as a family computer, in a library, or a workplace. While many shared devices automatically delete cookies when people log out of their local account (most notably larger businesses), if the cookies are not deleted, multiple submissions may have the same user ID but still come from separate people.
Remember, this is one way to potentially identify duplicate submissions that we introduced based on feedback. The best way to prevent them remains using registered participation. Caution must always be used when using the user ID to identify and delete duplicates.