WhatsApp co-founder Jan Koum announced he is stepping down as CEO, reportedly due to clashes with parent Facebook over user data, encryption and how to monetise the messaging app.

“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,” he said in a statement on Facebook, adding that he is “taking some time off to do things I enjoy outside of technology”.

“I’ll still be cheering WhatsApp on – just from the outside,” added Koum, who will also step down from Facebook’s board of directors.

While Koum did not explain his reason for leaving, a report in The Washington Post said he was not happy with Facebook’s attempts to use the personal data of WhatsApp users and weaken its encryption standards.

The high profile Cambridge Analytica data privacy leak might have been the last straw, although the report said Koum had his made his decision before the scandal.

Meanwhile Facebook CEO Mark Zuckerberg replied to Koum’s post, saying he was “grateful for everything you’ve done to help connect the world, and for everything you’ve taught me, including about encryption and its ability to take power from centralised systems and put it back in people’s hands. Those values will always be at the heart of WhatsApp.”

Disagreements

Reportedly both Koum and co-founder Brian Acton, who left in November 2017, were against Facebook’s efforts to commercialise WhatsApp, which has no advertising.

They also clashed with Facebook over building a mobile payments system on WhatsApp in India, and believed opening up the app to businesses would weaken encryption.

The executives did not want WhatsApp’s data going towards creating a user profile across Facebook’s multiple platforms, including Instagram and Messenger, that would be used for ad-targeting or data mining.

In August 2016, WhatsApp updated its terms and privacy policy, as it looks to “coordinate more with Facebook” and “test ways for people to communicate with businesses”.

The move was met by backlash from regulators in the US and Europe.

The Washington Post report revealed WhatsApp employees plan to leave in November when they are allowed to exercise all their stock options under the terms of the Facebook deal.

Facebook acquired WhatsApp for around $19 billion in 2014.