How it works
A retargeting campaign targets a defined group, such as users who have not opened the app for 30 days or who left items in a basket. The ad carries a deep link, so a tap opens the relevant screen. The measurement platform records the click and, when the app opens, attributes the session and the events that follow to the campaign within a re-engagement window. If the user had uninstalled the app and installs it again, this is usually reported as a re-attribution rather than a new install. On iOS, AdAttributionKit can report re-engagement in aggregate form.
Why it matters for an app team
Bringing back someone who already knows the app often costs less than finding a new user, and for apps with repeat purchases it is a large part of revenue. Without separate measurement these conversions are either invisible or mixed in with new installs, which distorts both.
In practice
Example with made-up numbers: a campaign reaches 50,000 lapsed users, 2,000 of them open the app from the ad and 300 make a purchase within seven days. Those 300 purchases are credited to the retargeting campaign, not to the campaigns that originally acquired the users.
Common confusion
A re-engagement is not a new install and should not be billed or reported as one. It is also different from push notifications and email, which are owned channels, although the same deep links can be used there. Building the audience lists is a separate capability from measuring the result.