Facebook first reached 1 billion daily active users in 2015. Mark Zuckerberg announced in August that more than 1 billion people had used Facebook on a single day, marking a major milestone for the social network.
This milestone is often confused with Facebook's earlier monthly-user achievement. Facebook reached 1 billion monthly active users in October 2012, but daily active users measure a much more frequent level of engagement. By late 2015, Facebook was reporting slightly more than 1 billion daily active users on average.
The achievement reflected Facebook's rapid expansion beyond its original college audience, particularly through smartphones and mobile internet access. It also showed why mobile apps and data connections had become central to the company's growth. Instagram and WhatsApp were already Facebook-owned by then, but the 1-billion daily figure referred to Facebook itself.