09Glossary
The mobile ad revenue dictionary.
Definitions for the words your monetization team uses every day — ad mediation, in-app bidding, eCPM, ARPDAU, ROAS, MMP, ATT, SKAdNetwork, and more.
Ad mediation
- A layer that routes ad requests across multiple demand sources (AdMob, AppLovin, Meta, Unity, IronSource, and others) to maximize fill rate and eCPM from a single SDK integration.
In-app bidding
- A simultaneous auction where every ad network bids on each impression. The highest bid wins. Mobile equivalent of header bidding. Typically lifts eCPM 10–30% over a pure waterfall.
Header bidding
- Web term for simultaneous ad auctions running before the ad server is called. In mobile apps the same pattern is called in-app bidding.
Waterfall
- Sequential ad mediation that queries networks one at a time in a fixed priority order. Each network gets the impression only if the higher-priority networks decline.
eCPM
- Effective cost per mille — revenue per 1,000 ad impressions. The primary metric for comparing ad networks and formats.
ARPDAU
- Average revenue per daily active user. The headline monetization KPI for ad-supported mobile apps. Combines fill rate, eCPM, and ad density.
ROAS
- Return on ad spend — revenue generated per dollar spent on user acquisition. The bridge metric between monetization and growth.
MMP
- Mobile measurement partner. Third-party SDKs (Adjust, AppsFlyer, Singular) that attribute installs and post-install events across ad networks.
ATT
- Apple's App Tracking Transparency framework. Gates IDFA access on explicit user opt-in. Introduced in iOS 14.5 and reshaped mobile attribution.
SKAdNetwork
- Apple's privacy-preserving attribution API. Reports install attribution without sharing user-level identifiers.
Fill rate
- Percentage of ad requests that return a paid ad. Low fill rate caps revenue regardless of eCPM.
Price floor
- Minimum eCPM accepted in the auction. Prevents low-value impressions from clearing and protects yield in high-value geographies.
Frequency cap
- Maximum number of ads shown to a user per session, day, or placement. Used to balance revenue against retention.
Rewarded ad
- Opt-in ad format where the user gets an in-app reward (coins, lives, extra content) for watching to completion. The highest-eCPM mobile format and the gentlest on retention.
Attribution
- The process of crediting an install or in-app event to the marketing source that drove it. Done by MMPs and, post-ATT, increasingly by first-party SDKs and SKAdNetwork.
Firebase-native
- Architecture where all ad and analytics events land directly in the publisher's own Firebase project (Firestore and BigQuery), keeping data residency with the publisher.