The move comes with Facebook struggling to cope with investigations and complaints over data protection and privacy, and after Zuckerberg's announcement last week of a new focus for the platform. The change reflects Facebook's changing audience and continued problems with serving as a conduit for misinformation and vitriol. He had left a graduate program at Stanford University to join Facebook in 2005 as a software engineer and helped developed its original news feed feature.
Cox "is a great guy who is someone who has always tried to do good", said David Kirkpatrick, an author who became well acquainted with Cox and Zuckerberg while writing a book about Facebook. "He would not be leaving at this challenging time if there wasn't something else going on".
A long-time Zuckerberg confidante, Cox's departure timing suggests he may not have been on board with the new corporate vision.
"It is with great sadness I share with you that after thirteen years, I've chose to leave the company", Cox wrote in his post. "This place will forever be a part of me". "He believes deeply in providing end-to-end encryption to everyone in the world across our services", Mark Zuckerberg wrote in a blog post, welcoming Will Cathcart as the new head of WhatsApp.
Two top Facebook executives are leaving the company, and it's not clear what they're moving on to do. He pocketed $310 million in gains from exercising Facebook stock options from 2014 through 2017 alone, according to the company's filings with securities regulators.
Also departing is WhatsApp Vice President Chris Daniels, adding to a string of recent high-profile exits from Facebook's product and communications teams. He was named the head of WhatsApp less than a year ago.
The departures of Cox and Daniels come a day after a technical issue that limited use of Facebook and Instagram for most of Wednesday. Longtime Facebook executive Will Cathcart will take over Daniels' job running WhatsApp.
Numerous changes Zuckerberg outlined involve duplicating some of WhatsApp's features in Facebook's other messaging apps.
Daniels has been at Facebook almost nine years, and previously led the company's Internet.org effort, a project aimed at bringing internet access to developing countries. Zuckerberg wants to encrypt user content and make posts, messages, and photos ephemeral, much like Snapchat.