When ad revenue drops in a mobile game, the first reaction is usually:
“Did eCPM drop?”
But in practice, eCPM is only one part of the story.
For small mobile game and app teams, I think the better first question is:
Which driver actually changed?
A simple diagnosis usually starts with a few checks.
1. Did impressions change?
Revenue can drop even when eCPM is stable.
If impressions fell, the issue may be traffic, retention, session length, ad placement exposure, or a recent product change.
In this case, looking only at eCPM can send you in the wrong direction.
2. Did eCPM change?
If impressions are stable but eCPM drops, the issue may be demand-side:
- weaker advertiser demand
- country mix changes
- bidder/source performance changes
- floor price or waterfall changes
- seasonality
This is where country, ad format, and ad source breakdowns matter a lot.
3. Did fill rate or match rate change?
A revenue drop with stable traffic and stable eCPM can still happen if fill rate drops.
For example:
- rewarded video requests stay stable
- eCPM stays similar
- fill rate drops from 78% to 54%
In that case, I would check mediation, ad source availability, floor settings, platform status, and country-level fill first.
4. Is the problem concentrated in one country?
A global revenue chart can hide the real problem.
Sometimes the total drop is mostly caused by one high-value country, such as the US, JP, KR, or DE.
Checking country-level revenue, eCPM, impressions, and fill rate often makes the issue much clearer.
5. Is one placement or format responsible?
Rewarded video, interstitial, and banner ads behave differently.
If only one placement drops, the problem may be tied to:
- placement exposure
- ad request logic
- waterfall setup
- user behavior
- one specific ad source
This is more actionable than simply saying “revenue is down.”
Why I am thinking about this
I am building eCPM Bazaar, a small diagnosis workflow for mobile game and app developers who monetize with ads.
The idea is not to replace AdMob, AppLovin MAX, Unity LevelPlay, TopOn, or other dashboards.
The goal is simpler:
Help small teams quickly understand whether a revenue change came from eCPM, impressions, fill rate, country mix, placement, or ad source performance.
Question for developers
If you monetize a mobile game or app with ads:
- What do you check first when revenue drops?
- Do you usually look at eCPM first, or fill/match rate first?
- Would a simple daily diagnosis report be useful, or do existing dashboards already solve this well enough?
I would love to hear how other small teams debug ad revenue changes.