Facebook and Twitter don’t like to talk about how, exactly, their algorithms determine users’ interests. According to their privacy policies, both collect basic information you provide in your profile, like your birthday and gender, as well as details around your log-ins, like what devices you use and your location, and your posts and “likes.” Twitter and Facebook may also receive information from your browser cookies, what links you click, and third party apps that you’ve connected to your account. They might also be able to match additional info from their partners to you based on your phone number or email address.
Though the details of their algorithms aren’t clear, Facebook and Twitter are at least attempting to be somewhat transparent about the end result of those programs. Your Twitter and your Facebook ad settings allow you a glimpse into what social media companies (and the advertisers who pay them) think you’re into.