
Overview of Interstitials
Interstitials are web pages that appear prior to seeing a page’s main content or after, when scrolling. They are typically implemented to display advertisements (i.e. popup ads, download ads, signup forms), for users to accept cookies, or for users to confirm their age for restricted content. Google continuously updates its algorithm for the goal of providing users with the most relevant content they’re searching for. They aim to accomplish this in the fastest way possible with the most user-friendly experience possible.
What Update Did Google Announce?
Recently, Google has announced a ranking penalty that will affect mobile web sites with intrusive interstitials that block content and make it hard for the user to access. The statement from Google:
“Pages that show intrusive interstitials provide a poorer experience to users than other pages where content is immediately accessible. This can be problematic on mobile devices where screens are often smaller. To improve the mobile search experience, after January 10, 2017, pages where content is not easily accessible to a user on the transition from the mobile search results may not rank as highly.”
Google is mainly targeting overlays that cast a gray shadow on the page that sits behind the interstitial pop-up, preventing users from reading the content.
Which Interstitials Will Be Affected?
• Popups that interfere with the main content at any point after entry.
• Standalone interstitials that user must tap to dismiss before accessing the main content.
• Above-the-fold standalone interstitials where the main content sits underneath the fold.

Which Interstitials Will Not Be Affected?
• Interstitials with legal obligations such as cookie usage or age verification.
• Login dialogs with private content such as email or unindexable content behind a paywall.
• Banners using a reasonable amount of screen space and are easily dismissible (i.e. app-install banners from by Safari and Chrome).

Will This Affect App-Install Banners?
App-install banners will not be penalized if they do not interfere with the main content. Although Google will allow near-full page interstitials for cookies and age verification, app-install banners are required to use much less screen space.
Will This Affect AdSense Page-Level Ads?
AdSense Page-Level Ads do not seem to fit the criteria that Google is looking to penalize sites for. PLAs typically sit on the edge of the screen and are easily dismissible.
Why Do We Care?
If webmasters do not remove or greatly scale back on interstitials displayed on mobile pages, mobile sites will likely be penalized and not appear in SERPs at all. This can cause a drastic loss in traffic and revenue. Lead generation and call-to-action on mobile sites may be limited significantly with ads and banners being less visible. Sites that rely on revenue via organic traffic from mobile devices could likely go out of business if they do not comply with Google’s mobile interstitial requests.
Webmasters that have always followed the practice of publishing quality content that is easy to find, without any disruption of banners or ads will not see any negative impact on mobile site rankings. This update enforces the practice of providing a positive and helpful user experience, which Google continues to improve upon daily in its algorithm and machine learning.
What Should We Do Moving Forward?
Don’t panic. Webmasters can still implement banners and interstitial ads. A simple banner to promote your app in-line with the page’s content is acceptable. Interstitials that use less than 25% of screen space are acceptable. Webmasters and marketing teams are now challenged to execute more creative opportunities that engage users without interstitials. They can analyze mobile traffic sources and position their offers that better target users who are likely to convert. Test out your creative and friendlier user experience ideas and implement the best versions.
In the future, we will likely see Google taking away intrusive desktop interstitials. If your web site is using interstitials that violate the new update, here are some ways to comply with app download interstitials.
Source: https://webmasters.googleblog.com/2016/08/helping-users-easily-access-content-on.html