Event-based optimization, in-app advertising, post-install events, target ROAS, cost-per-engagement, mobile user acquisition — six phrases you’ll keep seeing in 2025 because they describe the fastest-growing way to buy app traffic. Instead of paying for sheer download volume, growth teams now feed ad networks real-time post-install events and let machine-learning bid engines chase revenue, retention, or level-ups — a shift that slashes wasted spend and lifts lifetime value.
Why the industry moved beyond CPI
Marketers discovered that an install often tells them nothing about future spend or retention. RetailDive called post-install events “the tool to correctly optimize app-driven marketing” back in the early days of app UA, foreshadowing the wave we see now. Google cemented the idea with Target ROAS bidding, which lets advertisers specify the dollars they want back for every dollar spent on in-app actions. Meta’s App Event Optimisation (AEO) followed the same logic, delivering ads to users most likely to complete a purchase, registration or level-up.
How today’s platforms execute EBO
TikTok’s May-2025 update expanded App Event Optimization so brands can target events like Purchase or Subscribe rather than installs, explicitly marketing it as the key to maximise LTV. Unity takes things further with a Cost-per-Engagement (CPE) offerwall that only bills advertisers once the chosen event fires— zero guesswork, zero wasted impressions.
DSPs are on the same path. Liftoff’s Cortex ML platform reports stronger ROAS after switching to event-based models across iOS and Android campaigns. AppLovin’s Total ROAS campaigns blend ad-revenue and IAP data so the algorithm can maximise dollars earned rather than installs delivered. ironSource offers two flavours: an Event Optimizer that targets high-quality installs around a specific event, and a ROAS Optimizer tuned to hit precise day-7 payback windows.
Data, Volume & Learning
Whichever platform you pick, one rule stands: feed conversion data early and often. AppsFlyer stresses that recording in-app events is “the ideal tool to determine the value of app users and traffic quality.” Incipia recommends choosing an event that fires at least ten times per day — and ideally within three days of install — so algorithms exit learning quickly. Most networks quote the same benchmark: 10–50 daily events per geo before smart bidding can stabilise.
Pricing models you’ll meet
- tROAS / Ad ROAS (Google, AppLovin, ironSource) bids toward a revenue goal.
- oCPC / tCPA (ironSource, OEM DSPs) adjusts cost per action dynamically.
- CPE (Unity) charges strictly on event completion.
Best practices at a Glance
Record every meaningful action — from tutorial complete to purchase — to give ML the richest signal. Keep an eye out for fraudulent receipts: both Meta and AppsFlyer advise server-side validation for purchase events to stop fake revenue poisoning your bids. Finally, remember that creative fatigue can kill even perfectly optimised bids; Unity’s engagement models help, but refreshing ads weekly still matters.
What comes next?
Apple’s SKAN 4 and Google’s Privacy Sandbox will extend attribution windows, making deeper-funnel events viable on both iOS and Android. Google already supports ad-revenue events in Target ROAS bidding — proof that the line between monetisation and UA is blurring fast.
