How to Set Up Dark Mode in Firefox for Browser UI and Websites

Firefox dark mode works on two levels: the browser interface and the websites you visit, which can be configured separately. The browser UI can be switched to a dark theme in Settings or by installing a dark theme from Mozilla's add-on store. Websites go dark either when they support the prefers-color-scheme setting, which Firefox reads from the operating system, or when a tool like the Dark Reader extension forces a dark theme on sites that lack one. For broader control, an advanced about:config preference can force dark mode on all sites without an extension, though it offers less fine-tuning than Dark Reader. The guide also notes that new tab extensions need their own dark mode settings.