Read your owners manual for your monitor settings.

Hi Tom, a global setting or filter might be most efficient, but if you want to limit changes to Firefox: The built-in Firefox Home / new tab page allows adding a background color. See the wallpaper section of this article: [[Customize your New Tab page to hide or display content]]. To set something more global, Firefox has theme and setting options to control built-in pages: (1) Set the Website Appearance to Dark (affects built-in pages and some others) - [[Change website appearance settings in Firefox]] (2) Switch from System theme to Dark theme (affects toolbars and menus) - [[Use themes to change the look of Firefox]] For the web in general, you could consider a dark theme add-on such as Dark Reader https://addons.mozilla.org/firefox/addon/darkreader/ And if you decide you don't want a dark theme, there are some add-ons that adjust overall page brightness. Here's an example, but I have not tested it myself: * Review: https://www.youtube.com/watch?v=kna9foKkkww * Main page: https://addons.mozilla.org/firefox/addon/adjust-screen-brightness/ ''Note that add-ons usually can't inject changes into built-in pages, or certain Mozilla sites.''