The milestone comes as Zuckerberg has revealed a new mission for the social network over the past few months. The company, which in the past had focused on connecting the world, is now shifting slightly toward bringing the world closer, a sentiment Zuckerberg echoed in his post announcing the user milestone.

"For 10 years, we focused on doing everything around connecting people with their friends and family," Zuckerberg told Forbes in a recent interview. "Now I think that there is a whole lot of similar work to be done around communities: Meeting new people, getting exposed to new perspectives, making it so that the communities that you join online can translate to the physical world, too."

In a Chicago speech last week, Zuckerberg said he strives for users to find "a sense of purpose and support" on Facebook.

"A church doesn't just come together," Zuckerberg said. "It has a pastor who cares for the well-being of their congregation, makes sure they have food and shelter. A little league team has a coach who motivates the kids and helps them hit better. Leaders set the culture, inspire us, give us a safety net, and look out for us."

The platform has come under scrutiny for its role in disseminating false information. But Facebook announced a new campaign on Tuesday to emphasize the "good" on Facebook, including personalized videos and "thank you" messages to users that react positively to posts and events.