Use Charcoal to experience Messenger in dark mode. Toggling dark mode with any theme is easy: click on the Messenger icon on the top left of the web page, and set your preference.
v1.3.0 (November 22) – Works with Messenger’s new update.
Messenger icon toggle on the top left of the web page to access preferences.
Choose between 3 themes: Charcoal, Midnight, and Deep Blue.
Toggle the extension on or off entirely, whenever you want.