Facebook acquired WhatsApp in a $19 billion deal in 2014. WhatsApp is a cross-platform mobile messaging app that was founded in 2009 and had over 450 million active users at the time of the acquisition. The acquisition was Facebook's largest to date and was aimed at gaining a larger share of the growing mobile messaging market and leveraging WhatsApp's large user base and rapid growth to diversify Facebook's revenue sources internationally. The summary analyzes the value of the deal, Facebook and WhatsApp's histories and stats, and reasons for the acquisition such as expanding Facebook's mobile presence and pursuing the growing direct messaging market.