According to Tech Crunch, Matt Idema, vice president of monetization product marketing at Facebook confirmed to them that this is part of Facebook's shift to mobile.

"Mobile is now a necessary component of effective marketing campaigns, and Facebook is helping millions of businesses understand their customers' purchase path across devices," he said.

"Dynamic Ads and Custom Audiences have mobile at their core and are delivering excellent results for businesses, so Facebook Exchange spending has shifted towards those solutions," he added.

Facebook unveiled FBX in 2012. Lately, the social networking website is being shifted to mobile advertising for better revenues. Facebook has also started selling video ads via its Audience Network platform.