As outlined on Statista:
With roughly 2.89 billion monthly active users as of the second quarter of 2021, Facebook is the biggest social network worldwide. In the third quarter of 2012, the number of active Facebook users surpassed one billion, making it the first social network ever to do so. Active users are those who have logged into Facebook during the past 30 days. During the first quarter of 2021, the company stated that 3.51 billion people were using at least one of the company’s core products (Facebook, WhatsApp, Instagram, or Messenger) each month.