A modern app usually earns from several ad networks at the same time, and something has to decide which network gets each impression. Ad Mediation is that decision layer. It sits between your app and your demand sources, checks what each one will pay for a given impression, and serves the ad that returns the most, all in the fraction of a second before the slot loads.

How it works

You integrate a single mediation SDK into your app instead of wiring up every network by hand. The mediation layer holds connections to all the demand sources you have signed up for and, on each ad request, works out which one should fill the slot. Its aim is to raise your effective earnings across the whole stack, which usually means lifting both your Fill Rate and your eCPM together. Mediation does not create demand by itself. It organizes the demand you already have so the highest-paying option wins each impression.

Waterfall vs. in-app bidding

Mediation picks a winner in one of two ways. The legacy Waterfall ranks networks in a fixed order, usually by their past eCPM, and offers each impression to them one at a time until one fills. It is simple but slow, and it can miss revenue when a network lower in the order would actually have paid more for that specific user. In-App Bidding replaces the fixed queue with a live auction where every connected source bids on the impression at once and the highest bid wins. Bidding reflects the true value of each impression and removes the manual work of maintaining tiers. Many publishers run a hybrid, with bidding sources competing against any remaining waterfall lines.

Why mediation matters for publishers

An app tied to a single Ad Network takes whatever that one source offers and loses money whenever a better price exists elsewhere. Mediation turns your inventory into a contest instead. More sources competing for each impression pushes the winning price up, and a wider pool of demand means more requests fill rather than going empty. You get higher yield from the same traffic, with one dashboard and one SDK to manage rather than many separate integrations.

Where an offerwall fits in your mediation stack

An offerwall is a separate kind of demand source, not just another banner network. It earns on completed offers rather than passive views, which is why it tends to post some of the highest eCPMs in the stack. Because it monetizes engaged users through a different mechanism, an offerwall captures revenue that banner and interstitial networks never would. RevU integrates alongside a publisher's existing mediation setup, so its offerwall runs next to the current networks and adds incremental revenue rather than replacing what already works.

Common mistakes to avoid

• Leaving stale waterfall tiers in place. Prices move constantly, so an order set months ago quietly costs you yield.

• Judging a source by eCPM alone. A high eCPM means little if that source rarely fills, so read it next to fill rate.

• Treating mediation as set-and-forget. The stack needs regular review as networks, floors, and demand shift.