Do you mean the browser, web pages or both?

For web pages open Settings > General > Web site appearance.

https://support.mozilla.org/en-US/kb/change-web-appearance-settings-firefox

For the browser, you can choose a theme which suits you.

https://support.mozilla.org/en-US/kb/use-themes-change-look-of-firefox

You can also use two files (which you have to create) called userContent.css (for pages including browser pages) and userChrome.css (for the browser interface), bookmarklets and user scripts.

Hey there!

In addition to what Terry has mentioned, you can also change the theme with Firefox Color. See here: https://color.firefox.com/ And here's an article on how to change the wallpaper of Firefox browser if you do not want an extension: https://vintagemind.github.io/blog/2022/change-background/

Hope I helped!

Bithiah

Can you attach a screenshot?

• https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem
• use a compressed image type like PNG or JPG to save the screenshot

Hey there!

If your problem has been solved, please mark any answer as the solution to let others know this thread is over. If your problem still persists, please tell so we can further assist you. Thank you!

Bithiah