"Welcome to F8! This has been an intense year!" he said, greeting developers with the day's biggest understatement.
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In his first public appearance since testifying before Congress, Zuckerberg wasted no time addressing the elephant in the giant room at San Jose's McEnery Convention Center.
"What happened with Cambridge Analytica was a major breach of trust," he said. "An app developer took data that had been shared with them and sold it.We need to make sure this never happens again."
Developers at the conference knew that too well, because Facebook temporarily stopped approving new apps as a result, while the company examined new restrictions on how data is shared with third parties. To cheers, Zuckerberg announced app reviews will re-open immediately, with some changes.
"Some of our developers have to go through an extra level of scrutiny to make sure they're actually using the data in the right way," explained Desiree Motamedi, Facebook's developer marketing lead.
Data privacy is part of a mounting list of issues dogging Facebook in recent months.
"And that goes for Russia interfering in elections, for fake news, for hate speech," Zuckerberg acknowledged.
For nearly the first 20 minutes of his keynote, Zuckerberg addressed all those issues, conceding Facebook wasn't ready for the 2016 election.
VIDEO: Mark Zuckerberg gives keynote at F8 Conference
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Mark Zuckerberg gives keynote at F8 Conference
"We will never be unprepared for this again," he said.
Developers attending the conference agreed the emphasis on earning back trust was what they were looking to hear, at a time when they're already hearing a lot about Facebook in the news.
"He did it in a very nice way, with some humor even, and it was really very authentic," said Christian Gleich, a developer visiting from Germany for the conference.
Rather than shying away from current events, Zuckerberg used them to introduce some of Facebook's newest features.
"Let's say your friend is testifying in Congress, for example," he said, to thunderous laughter and applause, as he introduced "Watch Party"-a new way to watch videos online with friends.
And almost giddy with laughter, Zuckerberg unveiled a big surprise: "We're announcing a new set of features coming soon around dating," he said.
CNET's Lexy Savvides said this is big news. "Match, which is the owner of Tinder and some other dating apps, their shares did take a big plunge on the stock market as soon as the announcement was made," she said.
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Zuckerberg said the dating features, including messaging, will be completely separate from the rest of Facebook, and they won't match you with your friends-just people who like the same things as you. Facebook sure knows a lot about that-unless you use the new feature called "clear history" which, as its name implies, clears your browsing history on Facebook, the same way it would in a web browser.
"This is the kind of control that we think people should have," Zuckerberg said.
He said more features like it are in the works.
Facebook also introduced a long-awaited piece of hardware at the conference: Oculus Go, the $199 stand-alone VR headset, is aimed at giving more people access to virtual reality. It includes a wireless hand controller, speakers that pipe sound to a user's ears through tubes in the headband, and optional prescription inserts for glasses wearers.
Oculus Go comes along with the introduction of new Facebook features, including "Rooms" and "Venues"-the VR equivalents of Watch Party.
"You can talk to your friends and experience the Facebook content at the same time," said Charmaine Hung, a technical progream manager at Oculus. "And get to experience all those great things you can do live, but now in VR."
Oculus Go is available to order immediately, and only needs WiFi to work-it doesn't require a smartphone.
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