In general, user recognition in Mapp Intelligence is based on cookies. If a user visits your website using the "Private Mode" (Firefox, Safari) or "Incognito Mode" (Chrome), his cookies are deleting automatically when he closes the browser. If a user visits your website again afterward, he cannot be recognized as a returning user with the help of cookies.
User recognition gets more precise if the user logs in on your website: If so, a Customer ID can be passed that allows to identify the user as returning visitor.
Further information can be found in the training chapter Basic Metrics.