Liking, messaging, clicking, posting—most of us do these things online without thinking twice. But whether we know it or not, our online activities contribute to an ever-growing digital portrait of who we are—one that is more public than many people realize. This portrait helps companies target content at specific consumers, helps employers look into your background, and helps advertisers track your movements across multiple websites. More and more, your activities in the real world will also create digital footprints—paying a road toll, walking past a security camera, or going from one cellphone to the next. Whatever data you create on or offline, you will be leaving digital footprints behind somewhere. This portrait helps companies target content at specific consumers, helps employers look into your background, and helps advertisers track your movements across multiple websites. More and more, your activities in the real world will also create digital footprints—paying a road toll, walking past a security camera, or going from one cellphone to the next. Whatever data you create on or offline, you will be leaving digital footprints behind somewhere.