The agreement also provides for an additional US$3 billion in restricted stock units to be granted to WhatsApp’s founders and employees that will vest over four years subsequent to closing.

WhatsApp has built a leading and rapidly growing real-time mobile messaging service, with over 450 million people using the service each month and 70% of those people active on a given day.

The acquisition supports Facebook and WhatsApp’s shared mission to bring more connectivity and utility to the world by delivering core internet services efficiently and affordably. The combination will help accelerate growth and user engagement across both companies.

"WhatsApp is on a path to connect 1 billion people. The services that reach that milestone are all incredibly valuable," said Mark Zuckerberg, Facebook founder and CEO. "I’ve known Jan for a long time and I’m excited to partner with him and his team to make the world more open and connected."

Jan Koum, WhatsApp co-founder and CEO, said, “WhatsApp’s extremely high user engagement and rapid growth are driven by the simple, powerful and instantaneous messaging capabilities we provide. We’re excited and honored to partner with Mark and Facebook as we continue to bring our product to more people around the world.”

WhatsApp’s brand will be maintained; its headquarters will remain in Mountain View, CA; Jan Koum will join Facebook’s Board of Directors; and WhatsApp’s core messaging product and Facebook’s existing Messenger app will continue to operate as standalone applications.