Jan Koum clashed with parent company Facebook over the social media giant’s attempts to use people’s personal data and weaken WhatsApp’s encryption, the Washington Post reported, citing people familiar with the issue.
Referring to co-founder Brian Acton, the WhatsApp CEO wrote on Facebook: “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.”
He did not provide a departure date and did not confirm whether he would be joining Mr Acton who left WhatsApp in September to start a foundation.
Mark Zuckerberg, Facebook’s CEO, commented on Mr Koum’s post, saying he was grateful for what he had taught him 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,” he promised.
European regulators want to stop or limit Facebook’s plans to use WhatsApp user data, including phone numbers, to develop products and target ads.
WhatsApp has suspended the plan but last week said it still wants to move forward eventually.
Stanford University alumnus Mr Acton and Ukrainian immigrant Mr Koum founded WhatsApp together in 2009.
Facebook bought the messaging service in 2014 for $19bn (£13.8bn) in cash and stock.
A major part of WhatsApp’s popularity is its encrypted messages which are stored on users’ phones, not on company servers, making it more private.
Since the Cambridge Analytica data harvesting scandal hit in March, there have been growing concerns about Facebook’s handling of personal information.
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WhatsApp’s management has always opposed advertising, saying they did not want to be “just another ad clearing house” where the engineering team “spends their day tuning data mining”.
They initially charged a £1 annual subscription fee but that was dropped in 2016 and they instead started charging businesses for specialised accounts.