Cross-device identification is the process of recognizing a user across different devices and kinds of device - desktop, smartphone, tablet, etc.
Cross-device identification needs a specific user identifier that is common to different devices.
User identification can be based upon login usernames. Most often used logins are Facebook, Google and Twitter usernames. It can also be a username tied to a specific website.
The specific user identifier can also be tied to the different devices associated with a unique user or household through device matching process based on IP adresses or other data.
Cross-device identification is complex and only applies to some specific contexts and some users.
Cross-device identification is a prerequisite to :