The business logic of an interruption
A free app still has to pay for development, servers, and support. One way to do that is to sell advertising: each time an ad appears, the app creates an opportunity to earn money from an advertiser. Pop-ups are hard to ignore, which makes them more valuable as attention-grabbers than a quiet banner—but they also make the app less pleasant to use.
That discomfort can support a second revenue stream. The app offers a paid tier that removes ads, often through a recurring subscription. The free version reaches people unwilling to pay upfront; the subscription earns money from people who value a smoother experience enough to pay regularly. The interruption makes the difference between the two versions visible.
Friction has a limit
This strategy works only while enough users tolerate the free experience and some decide the upgrade is worth its cost. Too few interruptions may not generate much advertising revenue or make the paid tier feel necessary. Too many can drive users away altogether, taking both their attention and the chance of a future subscription with them.
So the design problem is not simply how many pop-ups to show. It is how much friction users will accept before they stop using the app. A pop-up can therefore serve two purposes at once: it may earn money when displayed, and it may remind users that paying is an option. The revenue comes from balancing those purposes—not from annoyance alone.
