CPA (Cost Per Action)

Cost per action (CPA) is the price paid for a specific in-app event — a registration, completed tutorial, first deposit, subscription or purchase. Like CPI, it can be either a pricing model or a calculated metric.

CPA goals move optimization closer to business value. Instead of rewarding any install, the bidding system learns which impressions lead to users who complete the chosen event. The key is choosing an event that happens early enough to give the system frequent feedback, yet predicts long-term value well. For many apps that means a registration or first transaction rather than a later milestone. CPA campaigns need reliable event postbacks from your MMP to work.

If events are too rare for the system to learn from, a common approach is to optimize on an earlier proxy event first and move to the deeper event once volume is sufficient. Review the relationship between proxy and true value regularly, since it can shift as the product changes.