Facebook says an earlier issue that caused apps like Tinder and TikTok to crash has been resolved.
Their login system was causing the applications to freeze instantly on iPhones.
It's believed to be because of a problem with logins that are controlled by the Facebook Software Development Kit.
This is not the first time this has happened, with similar issues being reported earlier this year.
A spokesperson for Facebook says a code change triggered the bug but was identified and fixed quickly.
