Six weeks ago Facebook added an Easter Egg to Facebook Messenger which would let you access a Dark Mode in the app if you send someone a moon.
Now the app has been updated to make the change as simple as a toggle in Settings.
Facebook says Messenger’s dark mode provides lower brightness while maintaining contrast and vibrancy. Dark mode cuts down the glare from your phone for use in low light situations, so you can use the Messenger features you love no matter when or where you are. On AMOLED screens there is of course also a power saving versus using white screens.
Via the Verge