How do we ensure that the same participants do not re-enter the survey?

Attest-audience Surveys
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Attest-audience refers to those surveys where Attest provides the audience to you (rather than when you send the survey to your own audience, details of own-audience are set out further down this article).

We have a number of few security checks & measures in place to ensure that respondents are not able to answer the same survey more than once.
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These are:
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Internet Protocol (IP) address check - Unique IP address prevents duplicate respondents by ensuring that the IP address for the respondent is unique for the study (or group of surveys if we have exclusive samples)

Panelist ID (PID) checks - Upon joining a panel, a respondent is assigned a unique PID to identify the respondent across multiple studies. Unique PID prevents duplicate respondents by checking that the PID for the respondent is unique for both the survey (or group of surveys if applicable). Unique ID - PID alone isn't a unique identifier because you could, in theory, have another respondent with the same PID in another supplier (though highly unlikely, we don't risk it). So we use a unique ID (PID + Supplier code) as a unique identifier for extra security.

Own-Audience Surveys

For own-audience surveys, that is, when respondents receive the link to the survey directly from you, via email or social media for example. In that case, we use an essential cookie (JSESSIONID) to track users. This enables us to ensure respondents cannot retake an own-audience survey using the same device and browser, and it is also how we know that the respondent that answered the first question is the same respondent that answered the second question.

We have less control over the way respondents answer own-audience surveys and there are a few ways someone could retake an own- audience survey. These are: