Acronym for Platform for Privacy Preferences. An open W3C protocol that allows Internet users to control the type of personal information that is collected by the Web sites they visit. P3P uses User Agents built into browsers and Web applications to allow P3P-enabled Web sites to communicate privacy practices to users before they log on to the Web site. P3P compares the Web site’s privacy policies with the user’s personal set of privacy preferences, and it reports any disagreements to the user.