WhatsApp is the largest messaging service in the world with more than 1.5 billion monthly users. It is highly popular in India, Malaysia, Singapore, Argentina, Brazil, Mexico, South Africa, and several countries in Europe.
In a Facebook post, Koum said that it's "time for [him] to move on" and that he'll be taking time off to pursue non-technology related interests.
It's been almost a decade since Brian and I started WhatsApp, and it's been an amazing journey with some of the best people. But it is time for me to move on. I've been blessed to work with such an incredibly small team and see how a crazy amount of focus can produce an app used by so many people all over the world.Koum did not detail his reasons for leaving Facebook, but The Washington Post says he is departing because he has clashed with Facebook executives over the messaging service's strategy and Facebook's attempts to use WhatsApp personal data, monetize the service, and weaken its encryption.
I'm leaving at a time when people are using WhatsApp in more ways than I could have imagined. The team is stronger than ever and it'll continue to do amazing things. I'm taking some time off to do things I enjoy outside of technology, such as collecting rare air-cooled Porsches, working on my cars and playing ultimate frisbee. And I'll still be cheering WhatsApp on - just from the outside. Thanks to everyone who has made this journey possible.
In addition to leaving WhatsApp, Koum is also said to be planning to step down from Facebook's board of directors.
Koum's disagreement with Facebook is said to have heightened following the Cambridge Analytica scandal where Facebook allowed data from millions of Facebook users to be collected by a third-party app, with that data then used to influence the 2016 U.S. presidential election.
Koum did, however, plan to leave Facebook before the Cambridge Analytica scandal came to light, as there have reportedly been tensions between the two companies since Facebook first purchased WhatsApp.
Facebook originally promised not to share WhatsApp data with Facebook, but that changed less than two years after the acquisition, leading to ongoing disagreements over data sharing as Facebook has pushed for more and more crossover between the two companies.
According to The Washington Post, other WhatsApp employees are demoralized by the disagreements between Facebook and WhatsApp and are planning to leave in November when their stock options vest.