A mobile interstitial is a pop-up or overlay that covers most or all of a page’s content on a mobile device, commonly used for email sign-ups, app download prompts, or promotional offers, before a visitor can access the actual content they came for.
Google has specifically penalized intrusive interstitials that block content immediately upon landing from a search result, since they create a poor user experience — though smaller banners, legally required notices (like cookie consent), and interstitials that appear after genuine engagement are generally treated differently.
Businesses using pop-ups for legitimate marketing purposes should carefully consider timing, size, and dismissibility to avoid both a poor user experience and a potential ranking impact.
Interstitial impact is assessed as part of our Technical SEO service.