A post-install event, also called in-app event, is any action a mobile app user takes after downloading an app. An “event” definition can differ according to the app category or in-app actions but some of the most common post-install events are:

• Making In-App Purchase
  
  
• Registering or completing onboarding
  
  
• Interacting with an in-app advertisement
  
  
• Achieving a level in a mobile game
  
  
• Consuming in-app content
  
  
• Adding items to shopping card in a shopping app

In-app events can be tracked via MMPs (mobile measurement platform) and they are very important to track the performance of mobile advertising campaigns and app performance metrics including retention rate, lifetime value (LTV), churn rate, and more.