https://wccftech.com/facebook-begins-rolling-out-dark-mode-for-its-ios-app/

Facebook has begun rolling out a dark mode theme for its iPhone and iPad app. The feature is available to a limited number of users on iOS so far. Facebook has previously released dark mode for Messenger, Instagram and WhatsApp.

Unlike other companies, Facebook has been slow to rollout a dark mode for its main app. The company just recently launched a complete redesign for its website, along with a dark mode.