The announcement reflects the shifting behavior of people online, which for years has pointed toward slowing growth in social media.
Outside the United States, services such as WeChat and the Facebook-owned WhatsApp have seen explosive growth by focusing on messaging.
Publicly shared posts have at the same time presented major challenges for Facebook as conspiracy theories go viral and the company struggles to enforce its rules prohibiting hate speech and harassment.
If the changes begin to emphasize private conversations, Facebook will have less work to do enforcing speech rules, said Antonio Garcia Martinez, a former Facebook manager.
Facebook's shift in corporate focus, which Zuckerberg said would happen over a few years, would mean less sharing on services such as Facebook and Instagram and more private messages that cannot be seen by anyone else, including by people at the company, because theyd be encrypted.
WhatsApp messages are already encrypted end-to-end, which means the messages are not stored on WhatsApp's servers and the company can't read them or hand them over to authorities. Facebook's Messenger has a similar feature that users can opt into, and Zuckerberg said the company would work toward implementing the same encryption for all private communications.
That kind of data-sharing has raised concerns among some regulators, including Facebook's European regulator, because of user privacy or the lack of competition.
Alex Stamos, the former chief security officer of Facebook, said on Twitter that he was surprised by the post and noted that the changes would take time to implement.
Original article