This method of identifying visitors across devices is no longer recommended. See Cross-device Analytics in the Components user guide.
Cross-device visitor identification helps you connect visitors across multiple devices. Cross-device visitor identification uses the
visitorID variable to associate a user across devices. The
visitorID variable takes the highest priority when identifying unique visitors.
When you send a hit with a custom visitor ID, Adobe checks for any visitor profiles that have a matching visitor ID. If one exists, the visitor profile already in the system is used from that point forward and the previous visitor profile is no longer used.
visitorID variable is typically set after authentication, or after a visitor performs some other action that allows you to uniquely identify them independently of the device that is used. Effective identifiers include a hash of their username, email address, or an internal ID that does not contain any personally identifiable information.
After the customer signs in from each device, they are all tied to the same user profile. If the visitor later signs out on a device, they continue to belong to the same visitor profile because Adobe recognizes that the browser cookie on each device belongs to the same visitor profile. Adobe recommends using the
visitorID variable whenever possible in case the browser cookie is deleted.
Using your own custom visitor ID’s gives you more control over how visitors are identified, but it comes with its limitations.