A User ID (short: UID), is a unique string of characters that allows to identify users.
User Identification is used in various areas. User IDs can mostly be found as user identificatiers, which is needed for login. With the combination of the User ID (e.g. an e-mail address) and a password, users log in to apps, websites, computers, etc.
However, the UID is also used for tracking user behavior.
The User ID in tracking
Unlike the user ID for registration, where the ID itself is chosen by the user, in tracking the user ID is assigned automatically and randomly according to a certain pattern. It can contain numbers as well as letters and is assigned directly at the first page view.
These User IDs are also usually not linked to other customer data. The data cannot be merged with concrete names and addresses. Therefore the user ID is an anonymous form of user recognition.
Nevertheless, the user ID plays an important role in tracking in order to accompany users throughout the user journey and/or over several sessions, to analyze user behavior and – with the right tool – to provide personalized offers. A user ID can be assigned via a cookie or stored in the local storage of the browser. This allows the user behavior to be tracked until a user deletes the cookies or the local storage.