Facebook works in a dark mode for Messenger, and it is a true AMOLED black theme. It is hidden right now, but most of the code is there, ready and waiting to be activated. By sending a command with root access, you can enable this function right now.
Shout out to Redditor Vincent JoshuaET who discovered the method that we will describe below. Unfortunately, it does not work for iPhones, and it does not even work with ADB commands on Android, so you must be rooted to try out the hidden dark mode of Messenger. But you just have to do a command in a terminal emulator app, tap any options in a hidden menu and then activate the dark mode in Messenger.
First, since the hidden / inactivated blackout code is only included in the latest beta version of Facebook Messenger, you need to update the app. The easiest way to do this is to sideless the new version from APKMirror. Just click on the link below and then scroll down and click "Download APK." From there, start the file from the notification area, and then press "Install" to update Messenger.
You need to run a root command to enable dark mode, which means you need a terminal emulator app. You can use any such app of your choice, but if you need a recommendation here, our pick is the tried and true Terminal Emulator of Jack Palevich.
Now open your terminal emulator app and type "su" (without quotes) and then press Enter on the keyboard. You will be prompted to give the app Superuser Access (Terminal Emulator, not Facebook Messenger), then click "Grant" on the popup. You will now notice that the second command line starts with a hashtag instead of a dollar sign – that means the terminal is running with elevated permissions.
Then copy the following command and paste it into the terminal prompt and then press at Enter on the keyboard:
Start -n "com. facebook.orca / com.facebook.abtest.gkprefs.GkSettingsListActivity"
You will immediately be taken to Facebook Messenger's hidden flag menu where the low level tweak level can be applied to the text program. Point to "Search gatekeepers" here, then enter "dark" at the prompt and press "OK".
Then tap each of the results under dark header to change their values from " NO "to" YES ". When all three of them say "YES", back from this menu, you completely free the Facebook Messenger app by swiping it away from your latest apps menu.
Now open Messenger and tap your profile picture (or the silhouette icon) in the upper left corner to access the app's main settings menu. From here, scroll down to section Preferences and you will see a new option that was not there before – switch to "Dark Mode" and then press "OK" on the popup to verify your selection.
Messenger will now be completely black with white text and dark gray accents. Even if the popup you just saw the dark mode "will not appear anywhere in Messenger", all main menus have been treated with dark mode.