Facebook Inc. is pushing online retailers and other advertisers to speed up their mobile websites by factoring how long it takes an advertiser’s linked-to mobile web page to load into its ad auction calculation as to which ad it presents to users.

How fast a mobile website loads is important, Facebook argues, citing a recent Aberdeen Group report that found up to 40% of website visitors abandon a site if it takes 3 seconds to load.

“Nobody wants to wait ages for a website to load,” Facebook writes in a blog post. “A better mobile experience helps businesses form a stronger connection with the people interested in them. Plus, site abandonment hurts business objectives, like completing a purchase or filling out a form. It can also bring challenges to measurement—people often abandon sites before third-party site analytics have time to register a page visit. This can make it harder to track and optimize ad performance.”

Facebook yesterday began prefetching, or preloading, mobile ad content in the Facebook in-app browser even before a consumer taps a link. The technology could speed up a mobile site’s load time by 29%, Facebook says, which decreases the risk of a consumer abandoning a site.

Facebook’s move is in line with Google’s recently including mobile page load times into its search algorithm that determines search result rankings. Like Facebook’s prefetching of ads, Google offers Accelerated Mobile Pages, which is its technology that ensures an ad or article loads quickly. AMP is an open-source framework that allows businesses, including retailers and marketers, to build lightweight mobile pages that load nearly instantly on smartphones. The search engine giant recently announced AMP for Ads and an AMP ad landing page through its DoubleClick unit, which serves ads on the internet.

Unlike Google, which has been publicly calling for businesses to lower their page load times for years, this is the first time that Facebook has made that call, says Brian Klais, founder and president of mobile marketing and mobile search engine optimization firm Pure Oxygen Labs.

“This is confirmation that we live in a mobile-first world,” he says. “I know that retailers struggle with slow load times, in part because many of them have shifted to responsive design. But they need to figure out how to make their pages load quicker because this is a big deal. They need to take speed seriously.”

Responsive design is a format that adapts the look of a single website and codebase to the device a consumer is using, eliminating the operational headaches of maintaining separate websites for smartphones, tablets and computers. Because it carries the coding for multiple devices, responsive sites can load slowly.

There are techniques retailers can use to speed up their site, Klais says. To start, merchants should visit a Google site, https://developers.google.com/speed/pagespeed/insights, which helps retailers identify common mistakes on their mobile site. More advanced techniques include using an adaptive technology that adjusts the content it presents based on a user’s device.

In making its announcement, Facebook urged retailers to consider keeping consumers within Facebook’s own ecosystem. For instance, it suggested retailers use its Canvas ads, which rely on a HTML5 format. The format lets marketers break free of the tight text, image or video-centric post constraints that limit what their posts look like and how consumers can interact with them. Within a single Canvas post, for example, a retailer can mix video, still images, text and call-to-action buttons. When a consumer clicks or taps on a Canvas post in his news feed, the post then opens and takes over the user’s full screen without the consumer leaving Facebook.