Facebook is buying mobile messaging service WhatsApp for up to $19 billion in cash and stock, by far the company's largest acquisition.
The world's biggest social networking company said Thursday that it is paying $12 billion in Facebook stock and $4 billion in cash for WhatsApp. In addition, the app's founders and employees will be granted $3 billion in restricted stock that will vest over four years after the deal closes.
Facebook says it is keeping WhatsApp as a separate service, just as it did with Instagram, which it bought for about $715.3 million.
WhatsApp has more than 450 million monthly active users. In comparison, Twitter had 241 million users at the end of 2014.