WhatsApp CEO, Co-founder Jan Koum to Quit

Jan Koum, the CEO and co-founder of WhatsApp speaks at the Digital Life Design conference on Jan. 18, 2016, in Munich, south Germany. Tobias Hase/AFP/Getty Images

SAN FRANCISCO—The co-founder of WhatsApp, a messaging service owned by Facebook, with more than 1 billion daily users, said on Monday, April 30, he was leaving the company, in a loss of one of the strongest advocates for privacy inside Facebook.