Research confirmed that Facebook creates detailed dossiers on people who have never created an account. Through contact uploads, tracking pixels, and Like buttons embedded across the web, Facebook tracks approximately 40% of all browsing activity for both users and non-users. A 2012 data breach first revealed shadow profile data. In 2018, Mark Zuckerberg admitted to Congress that Facebook collects information on non-users. There is no opt-out mechanism for people who never joined.