Google has announced that they will be changing how they rank mobile websites that use app install interstitials. What is an app install interstitial? It is an ad or pop-up which asks you to download a mobile app – it blocks the content that you expected to see on the web page until you either close the ad or follow the call to action. This is a common technique to use for advertising on mobile websites to get more app users. The thing is, this technique can create a bad user experience regardless of how effective it might be for advertisers. As a result, Google is making changes to their mobile search algorithm to combat this as they see it as a growing issue for mobile web users. Websites that use an app install interstitial in a way that blocks the majority of the expected content will likely see ranking losses in mobile searches. The actual penalty appears to be that Google will not consider an offending website to be mobile friendly. The changes will go into affect on November 1st and it will be a part of how Google determines how to rank mobile websites. Google’s Mobile Friendly Test has already been updated to account for this new change. Google is suggesting to use less intrusive ads that don’t block the entirety of the page content, or use the built in app install banners currently supported by Safari and Chrome browsers.