Eleven years ago, Alexis Madrigal, senior editor of "The Atlantic" magazine, discovered that 56% of its traffic was coming from unknown private sources-not public platforms like Facebook or Twitter. He realized that if marketers were only tracking social media engagement, they were only seeing the tiny tip of the iceberg. There was so much more looming underneath that they knew nothing about. Hence the term dark social. That type of activity can't be seen. Dark social is a private communication channel. It involves one-to-one texts, group chats, group texts, and conversations on private social media communities via platforms like Slack,