Mozilla yesterday released Mozilla Firefox 63. Starting with this version, the browser follows the system app theme. If you set the 'Dark' theme as your system and app theme in Windows 10, Firefox will automatically apply the appropriate built-in theme. If you are not happy with this behavior, here is how to disable it.
Firefox 63 represents the branch built with the new Quantum engine. It comes with a refined user interface, codenamed "Photon". The browser now comes without support for XUL-based add-ons, so all of the classic add-ons are deprecated and incompatible. See
Thanks to the changes made to the engine and the UI, the browser is amazingly fast. The user interface of the app is more responsive and it also starts up noticeably faster. The engine renders web pages much faster than it ever did in the Gecko era.
Firefox 63 follows the system app theme. If you set the 'Dark' theme as your system and app theme in Windows 10, Firefox will automatically apply the built-in Dark theme, and vice versa.
If you don't like the new behavior of Firefox, which applies the appropriate theme (Light or Dark) that matches the system app theme in Windows 10, you can always change the browser's theme manually. Just select a theme you like and Firefox will remember your preference.
Stop Firefox from Following Light and Dark App Mode in Windows 10
- Open Firefox and click on the hamburger button to open the menu.
- Select the Customize item from the menu.
- A new tab Customize Firefox will open. Click on the Themes item at the bottom.
- From the list, select the desired theme, e.g. Dark.
The browser will remember your theme and won't adjust it any more.
The change can be undone at any moment. Just open the 'Customize Firefox' tab once again and select the Default theme from the list of available themes. This will restore the default behavior.
- Add App Mode Context Menu in Windows 10
- Enable AV1 Support in Firefox
- Remove Top Sites Search Shortcuts in Firefox
- Disable Ctrl+Tab Thumbnail Previews in Firefox
- Disable Updates in Firefox 63 and above
- Firefox 63: Everything you need to know
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