As the Facebook News Feed continues to be optimized to produce a better user experience, paying attention to these updates is critical to ensure your carefully crafted Facebook posts are seen and engaged with.
In this case, Facebook says that they will:
"show people more stories that will load quickly on mobile and fewer stories that might take longer to load, so they can spend more time reading the stories they find relevant."
Facebook already takes into account a user's network connection and speed when they create their personalized News Feed display. If someone is on a slow connection, Facebook is more likely to show them status updates and link posts, while someone on a fast connection might see more videos.
This latest change means that Facebook will estimate the load time for your website and factor that into the equation as well. Slow sites will be bumped down, even if the viewer is on a fast connection. That might dramatically influence your post's reach.
This is because loading times matter in a mobile world:
"As many as 40 percent of website visitors abandon a site after three seconds of delay."
It makes little sense to display content to users that they aren't going to stick around long enough to see.
Google has been factoring load times into their display algorithm for a while, so it is no surprise that Facebook is following suit. Since conversion rates are significantly affected by loading time, it is critical that your website displays the content quickly.
Facebook provides a nice list of actions and tools you can use to measure and improve your website loading time.