Mobile and desktop audiences are built using different technologies:
- Desktop campaigns "cookie" the user. Place a retargeting pixel on your landing page to capture desktop users.
Mobile campaigns collect device IDs. For mobile campaigns, you don't need to place a pixel anywhere.
If you're managing both mobile and desktop audiences, create one audience list for mobile and another audience list for desktop. Be sure to name them so that you can clearly tell which audience is mobile and which is desktop - you'll need this later when you're targeting to the audiences.
By building separate lists, you keep track of how many users are in your mobile audience pool and how many are in your desktop audience pool. This is important to know when you run retargeting campaigns in the future, because desktop users can't be retargeted on a mobile device without cross-device support.
Cross-Device Audience Extension
When a campaign enables cross-device support, the campaign targets users on the devices that have been identified by the first-party audience as well as any other devices that are known for the user. See Cross Device for details and an example.