Facebook has been steadily rolling out support for dark mode on its apps, but oddly enough, the main Facebook app itself was not part of this support. That could be changing soon because according to a tweet by researcher Jane Manchun Wong, it appears that Facebook is now publicly testing out the feature.
It should be noted that not everyone seems to be able to access dark mode on Facebook right now despite Facebook seemingly testing it in public. It is unclear how users can qualify to take part in the test, or if Facebook is simply rolling out in phases where eventually everyone should have access to it.
However, if you want to check if you have the feature enabled on your mobile device, all you need to do is go to your Facebook app, either iOS or Android, go to Settings & Privacy, and you should see Dark Mode there. From there, you’ll be able to force the feature on or off, or you can leave it to automatically change based on your system settings, so if you have dark mode enabled on your phone through a schedule, then the app will make the switch automatically as well.
If you don’t see the feature, that means that you aren’t part of the test right now, although it appears that the feature is rolling out to quite a few people, so maybe give it a while and hopefully it will eventually find its way to you.