This is how to enable the dark mode for all compatible websites in your Firefox.
## Firefox Config
To enable the Firefox Dark Mode open your Firefox' [about:config](https://support.mozilla.org/en-US/kb/about-config-editor-firefox) and add a **new** boolean `ui.systemUsesDarkTheme` and set it to `1`.
## Debugging
For debugging purposes you can switch between dark and light mode using the *Inspector* (right-click > Inspect):
![Firefox' Inspector dark and light mode](/upload/2021-05-15%20Firefox%20Inspector%20Dark%20Light%20Mode.png)