Facebook says hackers accessed data from 29 million accounts as part of the security breach disclosed two weeks ago.
The exact number hadn't been known before. Originally Facebook said 50 million accounts could have been affected, but Facebook didn't know if they had been misused.
The hackers accessed name, email addresses or phone numbers from those 29 million accounts. For 14 million of those accounts, hackers got even more data, such as hometown, birthdate, the last 10 places they checked into or 15 most recent searches.
One million accounts were affected but hackers didn't gain information. The social media service plans to send messages to people whose accounts were hacked.
Facebook says third-party apps and Facebook apps like WhatsApp and Instagram were unaffected by the breach.