A young girl poses provocatively in a dark hotel room. For a set fee, any willing customer can pay to have sex with her. For investigators attempting to track down sex traffickers and their victims, these online advertisements can contain critical clues. The smallest of details in a room could give away its location, but there are too many ads for law enforcement to scan each of them for clues. That’s where TraffickCam comes in. It’s a simple phone app that uses crowdsourced snapshots of hotel rooms to help law enforcement locate victims and prosecute sex traffickers.