Firefox has respected Windows 10’s dark mode setting for a while now. But you can manually enable dark mode in Firefox, on any operating system, and without installing any third-party themes. This works on Windows 7, Windows 10, Windows 11, macOS, and Linux.
To change your Firefox theme, click the menu button (three horizontal lines) in the top right, then click “Add-ons and themes” in the drop-down menu.
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Click “Themes” at the left side of the add-ons page.
There are a handful of pre-installed themes, including Dark, Light, and System Default.
The System Default theme is a standard light theme that respects your Windows theme settings.
The Dark theme is Firefox’s dark mode. Everything in Firefox — including the title bar, toolbars, and menus — will turn black or a dark shade of gray with the dark theme.
The Light theme uses lighter grays. When you enable this theme, Firefox will use a light gray title bar and other elements, even when you have colored title bars enabled in Windows.
To enable the Dark theme — or any other theme — click the “Enable” button to the right of it. Firefox’s theme will instantly change.
You can install more themes from the Themes section of the Mozilla Add-ons website. The default Firefox dark theme is elegant and minimalist, but if you’re looking for something more specific, there are a huge number of dark themes available.
If you’ve enabled Firefox Sync, your selected theme will be synchronized to any other computers on which you’ve signed into Firefox.