In-app marketing is a crucial aspect of engaging and retaining users within an app. It involves using real-time and personalized messages to help users get the most out of the app, whether it's onboarding new users, introducing new features, or collecting user feedback. A well-planned in-app marketing strategy can increase user acquisition, guide users toward positive outcomes, capture user feedback, collect positive reviews, and drive sales. Effective techniques include using notifications, tooltips, splash pages, in-app messages, and modals to communicate with users and encourage desired behaviors. To set up an in-app marketing campaign, one must first define a strategy based on understanding user behavior, choose the right tools such as analytics platforms and message-building technologies, and test and iterate on the strategy to optimize results. By implementing these strategies, businesses can create a more engaging and valuable experience for their users, leading to increased retention and growth.