Google has announced that it will begin cracking down on “intrusive interstitials” on January 10, 2017, because this type of ad “can be problematic on mobile devices where screens are often smaller.”

Google will be potentially penalizing — i.e., lowering the rankings — of these web pages. Google said “pages where content is not easily accessible to a user on the transition from the mobile search results may not rank as highly.”

Google explained which types of interstitials are going to be problematic, including:

Showing a popup that covers the main content, either immediately after the user navigates to a page from the search results, or while they are looking through the page.

Displaying a standalone interstitial that the user has to dismiss before accessing the main content.

Using a layout where the above-the-fold portion of the page appears similar to a standalone interstitial, but the original content has been inlined underneath the fold.

Here is a diagram from Google to convey the above points:

Google listed three types of interstitials that “would not be affected by the new signal” if “used responsibly.” Those types are:

Interstitials that appear to be in response to a legal obligation, such as for cookie usage or for age verification.

Login dialogs on sites where content is not publicly indexable. For example, this would include private content such as email or unindexable content that is behind a paywall.

Banners that use a reasonable amount of screen space and are easily dismissible. For example, the app install banners provided by Safari and Chrome are examples of banners that use a reasonable amount of screen space.

Here is a diagram from Google to convey the above points:

In November 2015, Google launched app install interstitial penalty. Google is doing away with that version and somewhat rolling in that penalty with this new interstitial penalty. Google wrote:

We previously explored a signal that checked for interstitials that ask a user to install a mobile app. As we continued our development efforts, we saw the need to broaden our focus to interstitials more generally. Accordingly, to avoid duplication in our signals, we’ve removed the check for app-install interstitials from the mobile-friendly test and have incorporated it into this new signal in Search.

Search Engine Land will stay on top of this rollout when it happens next year.