Facebook Beacon was the advertising program that tracked and reported users’ activity on websites outside Facebook.
Launched on November 6, 2007, Beacon transmitted information from participating third-party websites to Facebook. Activities such as purchases could appear in users’ News Feeds, sometimes without their clear knowledge or consent. The initial system included 44 partner websites.
Beacon caused a major privacy backlash because users initially had little control over whether their off-site actions were shared. A class-action lawsuit followed, and Facebook eventually agreed to a $9.5 million settlement. The service was shut down in September 2009; Mark Zuckerberg later called Beacon a mistake.
Beacon is often confused with Facebook Pixel, a later tracking and advertising measurement tool, or Audience Network, Facebook’s ad-placement network. Beacon’s distinctive feature was its controversial sharing of activity from external sites back to Facebook.