What mechanism does the "Prevent multiple submissions" feature rely on?

The "Prevent multiple submissions" feature primarily relies on browser cookies. When this feature is enabled, a unique cookie is placed in the respondent's browser when they submit their survey. This cookie acts as a marker that prevents the individual from submitting the survey again from the same browser.

By using cookies, Qualtrics can effectively track submissions on a browser-specific basis, thus protecting the integrity of the data collected by ensuring that each participant's responses are counted only once. This method is straightforward and operates at the browser level, making it an efficient way to manage responses without requiring participants to create accounts or modify their user behavior significantly.

While email verification could prevent multiple submissions if a unique link was sent to each respondent, it's not the mechanism used in this specific feature. Similarly, user ID recognition and online session tracking may have relevance in user authentication and data collection but do not represent the primary method used to prevent multiple submissions in Qualtrics. The reliance on browser cookies is what makes this feature particularly user-friendly and effective for survey administrators.