Ad spending on social media continues to grow at impressive rates and is taking increasingly more share of marketers’ interactive marketing budgets. Engaging and more interactive formats on mobile devices and better targeting capabilities are the main drivers of the increasing spend on social networks. We expect new mobile app-only social networks and fast-growth ad formats such as video to fuel growth in the future. The forecast details US social media advertising spending and includes a breakout of social media ad spending by mobile and desktop.