Two months ago, Google warned us that app interstitials may lead to a penalty, if they take up too much of the page, covering most of the content. Well, yesterday, November 2nd, that penalty went live into the overall mobile friendly algorithm.
Google posted the news yesterday afternoon on Google+ saying:
An update to the mobile-friendly algorithm
Starting today, pages with an app install interstitial that hide a significant amount of content on the transition from the search result page won’t be considered mobile-friendly.
Instead of full page interstitials, we recommend that webmasters use more user-friendly formats such as app install banners. We hope that this change will make it easier for searchers to see the content of the pages they are looking for.
No one should be surprised by this but I have yet to see people complaining in the forums that their sites were hit by this penalty.
Forum discussion at Google+.