Use Charcoal to experience Messenger (messenger.com) 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.

Features:
Messenger icon toggle on the top left of the web page to access preferences.
Choose between 3 themes: Charcoal, Midnight, and Deep Blue.
Change dark or light appearance whenever you want, or set dark mode based on your device's setting.