What is Ad Mediation?
Also known as: Mediation platform, Ad mediation layer
What is ad mediation?
Ad mediation is a software layer inside a mobile app or CTV app that sends one ad request to many ad networks at the same time, picks the highest-paying response, and serves it. It replaces the manual job of calling each network in sequence.
A publisher with 10 ad networks would otherwise need 10 SDKs, 10 dashboards, and 10 sets of priority rules. A mediation platform collapses all of that into one SDK and one waterfall or auction. It handles SDK initialization, request fan-out, response timing, and revenue reporting in a single layer.
The math is simple. More bidders on the same impression means more competitive pressure. More pressure means higher eCPM and higher fill rate. For most in-app publishers, mediation is the single biggest revenue lever after launching the app itself.
Waterfall vs in-app bidding mediation
Mediation has two architectures. Waterfall is the legacy approach. In-app bidding is what every major platform pushes in 2026.
| Dimension | Waterfall mediation | In-app bidding mediation |
|---|---|---|
| Auction type | Sequential, ranked by historical eCPM | Parallel, real-time, single auction |
| Latency | High. Each network call adds 200 to 800 ms | Low. All bids return in one round |
| Pricing visibility | Estimated. Networks bid against a stale floor | Actual. Every network bids the live impression price |
| Configuration | Manual instances, priority tiers, eCPM floors | Automatic. Bidders compete openly |
| Typical eCPM lift vs single network | 5 to 20 percent | 15 to 40 percent |
| Status in 2026 | Deprecated for new apps | Default in AppLovin MAX, AdMob, Unity LevelPlay |
In-app bidding is what header bidding did for the open web, applied to mobile. The IAB Tech Lab OpenRTB 2.6 spec standardizes the bid request format both auctions use.
Major ad mediation platforms
Four platforms control most of the in-app mediation market. The choice usually comes down to which networks the publisher already runs and which app store the app lives in.
| Platform | Owner | Best for | Networks supported | Auction type |
|---|---|---|---|---|
| AppLovin MAX | AppLovin | Gaming apps, rewarded video heavy | 25+ networks, all major demand | In-app bidding (default) |
| Google AdMob | Long-tail apps, AdSense overlap | 15+ networks plus AdMob's own demand | Bidding plus waterfall | |
| Unity LevelPlay | Unity (acquired ironSource 2022) | Unity-built games, ironSource alumni | 20+ networks, deep gaming demand | In-app bidding (default) |
| ironSource LevelPlay | Unity (same brand) | Hyper-casual, mid-core gaming | Same stack as LevelPlay | In-app bidding |
| Meta Audience Network | Meta | Apps with social ad spend overlap | Meta only, used as a demand source inside other mediators | Bidding |
Public docs: Google AdMob mediation, AppLovin MAX, Unity LevelPlay. Each platform publishes SDK integration guides, network adapter lists, and revenue benchmarks.
How a mediation auction picks the winning ad
The flow takes about 300 milliseconds end to end. The mediation SDK in the app sends one bid request to every connected network in parallel. Each network returns a bid price plus a creative. The highest valid bid wins. The mediation SDK serves the creative and logs the impression.
Three filters run before a bid can win.
- Format and size match. A 320x50 banner request rejects a 300x250 bid.
- Floor price. A bid below the publisher's per-country, per-format floor is dropped.
- Brand safety and frequency caps. Per-user caps and blocked advertiser lists filter on the SDK side, not the network side.
The network that wins pays the second-highest bid plus one cent in a second-price auction, or the full bid in a first-price auction. AppLovin MAX, Unity LevelPlay, and AdMob bidding all use first-price by default in 2026. The shift mirrors what happened on the open web after Google Ad Manager moved to first-price in 2019.
Why mediation lifts eCPM and fill rate
Three forces compound when a publisher turns mediation on.
Auction pressure. Six bidders competing for one impression clear at a higher price than two bidders. AppLovin's 2024 mediation report showed an average 22 percent eCPM lift when apps added their fourth, fifth, and sixth in-app bidder.
Higher fill. With more demand sources, the chance that every request returns a paid ad approaches 100 percent. Rewarded video fill rates above 95 percent are standard once mediation is wired correctly. Banner fill clears 90 percent on most apps.
Lower latency tax. Parallel bidding finishes in one round trip, around 200 to 400 ms. A six-network waterfall can take 1.2 to 2 seconds and lose impressions when users close the app mid-load. Faster bids mean fewer dropped impressions, which means higher effective fill.
The combined effect is what app monetization teams call "stack lift." Most apps see a 25 to 50 percent revenue increase in the first two months after migrating from a single network or waterfall to a fully wired in-app bidding mediation stack.
Real-world example with numbers
A casual mobile game has 800,000 daily active users. It runs rewarded video and interstitials. Pre-mediation, it uses one network only.
Baseline numbers, 30-day window:
- Ad requests: 96,000,000
- Fill rate: 78 percent
- Filled impressions: 74,880,000
- Average eCPM: $9.40
- Monthly ad revenue: $703,872
The studio integrates AppLovin MAX with seven bidders (AppLovin Exchange, Meta Audience Network, Google AdMob, Mintegral, Pangle, Unity Ads, Vungle). Two months later:
- Ad requests: 96,000,000 (flat)
- Fill rate: 96 percent
- Filled impressions: 92,160,000
- Average eCPM: $12.80 (auction pressure)
- Monthly ad revenue: $1,179,648
Fill went up 18 points. eCPM went up 36 percent. Revenue went up 68 percent on the same traffic. This is a typical outcome on a gaming app moving from single-source to fully bid-enabled mediation.
Ad mediation in 2026
Three shifts define the current state of mediation.
Bidding is the default. AppLovin MAX and Unity LevelPlay are bidding-first. AdMob defaults new apps to bidding-enabled stacks. Pure waterfall setups are now treated as legacy by every major platform.
SKAdNetwork 4 and Privacy Sandbox shape the auction. iOS 14.5+ stripped IDFA from most users. Android Privacy Sandbox is rolling out to select users in 2025 and 2026. Mediation platforms now route deterministic and probabilistic signals through the bid request to keep CPMs from collapsing. AppLovin's AXON and Google's bidding ML close part of the gap.
Consolidation continues. Unity bought ironSource in 2022. AppLovin acquired MoPub from Twitter in 2021. The number of independent mediators keeps shrinking. Most apps now run two mediators in parallel as a hedge, AppLovin MAX plus AdMob being the most common pair.
For a new app, the practical move in 2026 is short. Ship with one mediation SDK. Wire 6 to 10 in-app bidders. Watch eCPM, fill rate, and ARPDAU together. Pair the data with ad revenue reporting at the placement level. The stack will pay for itself in the first revenue cycle.
Related terms
Frequently asked questions
What is ad mediation in simple terms?
Ad mediation is a referee. One ad slot, many ad networks. The mediation SDK asks every connected network what they will pay, picks the highest bid, and serves that ad. Without mediation, the publisher would have to call each network in sequence, lose time, and leave money on the table.
What is the difference between ad mediation and an ad network?
An ad network is a single source of demand. Meta Audience Network, AdMob, and Unity Ads are networks. Ad mediation sits one layer above and routes one impression to many networks at once. Publishers use a mediation platform to manage 5 to 15 networks from one SDK and one dashboard.
Is ad mediation free?
AppLovin MAX, AdMob mediation, and Unity LevelPlay are free to use. They make money on the ad network side, not the mediation fee. ironSource LevelPlay is also free. Some niche third-party mediators charge a revenue share of 1 to 5 percent. For most apps, the platform fee is zero.
Does ad mediation increase eCPM?
Yes, in nearly every case. Public benchmarks from AppLovin and Unity show eCPM lifts of 15 to 40 percent when an app moves from a single network or waterfall to in-app bidding mediation with 6+ networks. The lift comes from competitive auction pressure, not from any single network paying more.
Waterfall or in-app bidding, which mediation type wins?
In-app bidding wins on almost every metric. It runs a parallel real-time auction, returns one clearing price, and removes the priority guesswork that waterfalls require. AppLovin MAX moved fully to bidding in 2020. Unity LevelPlay and AdMob both default new apps to bidding-first stacks in 2026.