When you switch to the light or dark theme on Windows 10, supported apps also switch their mode to align with the color with the rest of the environment.
Although Firefox isn’t an app available from the Microsoft Store, it’s been updated to automatically follow the color theme you set on Windows 10. However, if you want Firefox to use a specific theme color no matter the mode you use in the operating system, you can quickly accomplish this by changing the browser settings.
In this guide, you’ll learn the steps to set a permanent default color theme on Firefox to prevent the browser from changing colors when you switch to light or dark mode on Windows 10.
How to set default theme for Firefox
If you want to prevent Firefox from changing the theme color to align with the color mode you set on Windows 10, use the following steps:
Click the menu (hamburger) button on the top-right corner.
Click the Customize option.
Select the theme (Light or Dark) that you want to use.
Once you’ve completed the steps, Firefox will remember your settings, and it won’t change it the next time you change your system color theme.
If you want to revert the changes, you can use the same instructions outlined above, but on step No. 4, make sure to select the Default option.