What is an Interstitial Ad?

An interstitial (interstitial ad) is a full-screen ad unit shown at a transition: between app screens, game levels, or site pages. The creative replaces the host interface until the user closes it — immediately or after a short delay. The view counts as an impression. It is inventory, not a buying channel: catalogs file it under both in-app ads and web display.

Where it appears

In apps, networks load interstitials via SDK at “natural breaks”: after a level, on a section change, when a task ends. On mobile web they sit between publisher page navigations. On desktop, full-screen units are less common and overlap pop-ups and takeovers. IAB descriptions treat an interstitial as the full viewport, not a 300×250 banner in the article body.

Creatives may be static images, HTML5, video, or playable. Size follows device orientation rather than a fixed banner rectangle. A close control (X, Skip, swipe) is required by most network policies; a unit with no exit is treated as aggressive and is rejected.

Versus rewarded

Rewarded ads (usually rewarded video) are user-started in exchange for in-game currency, a life, or unlocked content. Completion is high because the watch is the condition for the reward. An interstitial offers no bargain: it interrupts the session at a transition. The economics differ. Rewarded units see higher completion and fewer accidental clicks. Interstitials take the whole screen and often post a higher eCPM than banners, with more accidental clicks and UX complaints.

Advertisers see different intent. Rewarded inventory often carries app offers and CPI, where the user already agreed to “watch an ad.” Interstitials behave like classic display: reach, retargeting, an install or lead from the creative with no explicit reward. Mixing the two formats in one report without a split is useless: CTR and post-click CR are not comparable.

Versus banners and pop-ups

Banner / MREC display occupies a slot inside the UI. An interstitial replaces the UI until dismissed.
Pop-up / pop-under opens a new window or overlay, often outside the navigation path. An interstitial is meant as a planned slot in the flow (between screens), not an overlay at load.
In-stream video lives in a player. A video interstitial is a full-screen spot at an app pause, not necessarily a VAST slot in a content player.

Buying and metrics

Publishers sell the slot in mediation: networks compete, the winner pays CPM or waterfall eCPM. Buyers purchase it in the same consoles as other in-app and display: Google Ads App campaigns, Meta, TikTok, DSPs, SDK networks. Billing may be impression- or click-based; the platform can still optimize to CPA or CPI on the same unit.

CTR alone misleads. A full-screen creative inflates clicks via area and mis-taps near Close. More useful: viewability (usually high — the creative fills the screen), bounce and post-click CR in the tracker, install→event chains, complaints, and close rate. Repeated interstitials in one session cut the source app’s retention and the advertiser’s traffic quality.

Platform policies

Google Play and AdMob forbid interstitials on app launch, on exit, and mid-task (typing, an unpaused level). The break must be natural. Google Search separately describes intrusive interstitials: a full-screen layer that blocks content right after a SERP click can hurt page evaluation. That rule is for sites, not the AdMob auction. A landing-page interstitial and an in-app slot sit in different compliance boxes.

Gambling, dating, and nutra more often hit creative policy than the format itself. A misleading fullscreen on a web landing raises disapproval risk regardless of the unit name in the console.

Limits

An interstitial does not create search intent: it is a push impression, like other display, unlike search ads. On iOS, SKAdNetwork and ATT still constrain install measurement; a fullscreen click does not restore user-level postbacks. If the optimization goal is a click rather than a conversion, accidental taps poison platform learning. For the publisher, high frequency breaks the product; for the buyer, the same slot can yield cheap clicks with zero LTV.