messenger-web-dark

This is a single-line Chrome extension: document.querySelector('html').classList.add('__fb-dark-mode');

Messenger Web already has built in support for a dark mode, but no actual setting anywhere to turn it on. This extension runs the line above whenever a Messenger tab is loaded, enabling the "secret" dark mode.

Installation

1. Download and unzip the repository
2. Go to chrome://extensions
3. Enable Developer Mode
4. Hit Load unpacked
5. Navigate inside the extension folder and click Select Folder