Facebook has expanded its ad apparatus over time by continuously accumulating details about its users and turning those details into targetable data points.
When Facebook introduced its ad platform in 2007, advertisers could target people using information they had volunteered on the platform.
Three years later, Facebook introduced Custom Audiences, a feature that allowed companies to upload their own lists of people to target. A retailer, for example, could upload its customer list and target ads at those who had recently bought a specific kind of T-shirt.
In mid-2014, Facebook incorporated users’ online browsing history into its ad-targeting platform. The company had been collecting browsing data for years, from any web page that included a Facebook like button or had let people log in through their Facebook accounts.
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