A system and method for unifying user-level data across a plurality of media platforms are provided. The method includes receiving user-level data events from the plurality of media platforms, wherein each event relates to at least one online advertisement viewed by a plurality of users; processing the received user-level data events to detect a group of user-level data events related to the same user of the plurality of users; combining user-level data from each group of user-level data events related to the same user; assigning a unique user identifier to the combined user-level data to result in a unified user-level data related to a particular user; and storing the unified user-level data in a database, thereby providing consistent user-level data across the plurality of media platforms.