SAN FRANCISCO — When Facebook bought the start-up WhatsApp in 2014, Jan Koum, one of WhatsApp’s founders, declared that the deal would not affect the digital privacy of his mobile messaging service’s millions of users.
“We don’t know your birthday. We don’t know your home address,” Mr. Koum wrote in a blog post at the time. “None of that data has ever been collected and stored by WhatsApp, and we really have no plans to change that.”
Two years later, in a move that is rankling some of the company’s more than one billion users, WhatsApp will soon begin to share some member information with Facebook.
WhatsApp said on Thursday that it would start disclosing the phone numbers and analytics data of its users to Facebook. It will be the first time the messaging service has connected users’ accounts to the social network to share data, as Facebook tries to coordinate information across its collection of businesses.