Facebook reported having 1 million users by the end of 2004, its first year online.
The service began at Harvard University in February 2004 under the name TheFacebook. It soon expanded to other American universities, including Stanford, Columbia, and Yale, before becoming available to more schools and eventually to the general public.
Reaching one million users within its first year was an important early milestone. At that stage, Facebook was still primarily a university social-networking service rather than the global platform it later became. Its early growth was driven by school-based networks, where users commonly joined using institutional email addresses.
This figure is often confused with later Facebook milestones. The company reached 5.5 million users by the end of 2005 and 12 million by the end of 2006. Those numbers represent later stages of expansion, after the service had spread beyond its initial Harvard audience.