An ad unit is the building block of in-app monetization. It is one defined slot where an ad can appear, with a set size, position, and rules for how and when it shows. When a publisher plans how an app will earn from advertising, they are really deciding which ad units to place, where to put them, and how often to show them.

How it works

Each ad unit is configured in the app's ad SDK and mapped to one or more demand sources. When a user reaches a point where the unit is allowed to show, the SDK requests an ad, an auction or waterfall decides which advertiser wins, and the creative renders inside the slot. The unit then reports impressions, clicks, and revenue so the publisher can see how it performs. Because every unit has its own size and behavior, each one also carries its own typical eCPM, fill rate, and effect on the user experience.

Common ad unit types

• Banner ad. A small strip that stays on screen during use, with low earnings and low friction.

• Interstitial ad. A full-screen ad shown at natural breaks, earning more but interrupting more.

• Rewarded video. An opt-in video that grants a reward on completion, with high engagement and eCPM.

• Native. An ad styled to match the surrounding content so it blends into the feed.

• Offerwall. A browsable menu of offers users opt into in exchange for a reward.

Forced vs. opt-in units

Some ad units interrupt the user without asking. A banner sits on the screen and an Interstitial Ad blocks it at a break. Others are opt-in: the user chooses to engage in exchange for something. Rewarded Video and the offerwall both fall into this second group, which is why they tend to be better tolerated even though they can earn more per user. Sorting your units this way is often more useful than sorting them by size.

Why the ad unit mix matters

No single unit monetizes an app well on its own. Banners earn a little from almost everyone, interstitials earn more at a cost to session flow, and rewarded formats earn the most from users who choose to engage. Publishers tune the mix to balance revenue against retention, and they watch each unit's eCPM and its effect on churn rather than judging units in isolation.

The offerwall as a high-value ad unit

The offerwall is the ad unit users opt into rather than have forced on them. Instead of a single creative, it presents a menu of offers, and it earns on completed actions rather than passive views. Because a completion is worth far more than an impression, a well-placed offerwall often posts the highest eCPM in the stack while giving users a reason to return. It fits naturally alongside Rewarded Video as the opt-in half of a healthy ad unit mix.

Common mistakes to avoid

• Stacking too many interruptive units so ad frequency drives users away.

• Judging a unit by eCPM alone while ignoring fill rate and its effect on retention.

• Treating every placement the same instead of matching the unit to the moment in the session.