Interstitials

What it actually is

A full-screen ad shown between content transitions — usually a page reload, an article-to-article jump, or a video segment break. The unit takes the whole viewport, has a visible close button (or a forced 5-second timer on some networks), and runs frequency caps to keep the same user from seeing more than one per session.

Inside PropellerAds the interstitial book was the second-largest format after popunder for iGaming verticals in 2021–2022. The reason: when popunder fill softened on tier-2 LATAM (Brazil, Colombia, Mexico) due to publisher rotation, interstitials picked up the deposit-conversion volume at a CPM premium of roughly 20–35%.

Why it works

• Maximum visual impact — full viewport, no scroll competition, no banner blindness
• Fine-tuned templates per vertical: iGaming uses the bonus-stack creative, utility uses the install-CTA template, dating uses the SOI-flow shortcut
• Mobile and desktop, with mobile carrying the dominant share for iGaming
• Frequency capping protects publisher UX — no network worth using runs uncapped interstitials

Best for

• iGaming player attraction at scale, especially during tier-2 LATAM popunder softness windows
• App download campaigns where the install-CTA template earns its keep
• Popunder-scaling — when your popunder campaign saturates on a publisher, interstitial picks up the residual budget at higher CPM but similar CR
• eCommerce flash-sale and time-limited offer creative

What it is not

Interstitials are not the right call when the publisher’s audience has high session depth. A reader who’s three articles in to a long-form magazine piece does not appreciate a full-screen takeover, and the CR reflects that. The format works on session-shallow inventory — news aggregators, sports score sites, utility-tool publishers — and gets punished on session-deep inventory.

Specs

• Pricing models: CPM and CPA. CPA-goal works well here once you have postback volume — the optimiser handles frequency-cap arbitrage automatically
• Devices: Mobile and desktop. Mobile carries roughly 75% of interstitial conversion volume for iGaming
• GEO coverage: 240+ countries. Tier-2 LATAM is where interstitials earned their keep in my book, but the format scales tier-1 too
• Anti-fraud: Multi-layer filtering plus ML scoring on each impression. Frequency cap data also feeds the fraud filter — a single device hitting interstitials at a non-human rate is the easiest fraud signal in the catalogue