Google has announced that it be introducing a new rule to its search ranking algorithm in January 2017, which will downgrade sites which hit users with intrusive interstitials in its search results.

This change wont include all types of interstitials – messages about cookie usage or for age verification and log-in dialogues are fine – but many ads will fall foul of the new rules.

Any non-vital pop-up that obscures the main content of the page, interstitials that have to be dismissed before reaching the content, and layouts which put a full-screen ad above the fold will all count against sites.

The exception are banners that use a reasonable amount of screen space and are easily dismissible – Google gives the example of Safari and Chromes app install banner format.

“Pages that show intrusive interstitials provide a poorer experience to users than other pages where content is immediately accessible,” said product manager Doantam Phan, in Googles announcement of the changes. “This can be problematic on mobile devices where screens are often smaller.”

Google started penalising full-screen app install ads in its search algorithm last September, but this latest change broadens that rule to interstitials of all kinds.

Its reminiscent of the so-called Mobilegeddon tweak to Googles algorithm that came into affect last April, introducing mobile-friendliness as a factor in search rankings. Whether it will provoke the same panicked reaction in the industry – or get its own similarly apocalyptic nickname – remains to be seen but, after last time, Google has been careful to make it clear that this wont be the end of the world.

“Remember, this new signal is just one of hundreds of signals that are used in ranking,” said Phan. “The intent of the search query is still a very strong signal, so a page may still rank highly if it has great, relevant content.”