< back firefox-gtk.html

"For users who don't want any native theming in web content, Firefox has a built-in solution. In about:config, verify that widget.content.allow-gtk-dark-theme is false. If you use a theme that does not have a light variant (e.g, Arc Dark; the light version, Arc, is a separate theme), then create a new string entry in about:config called widget.content.gtk-theme-override and set it to a light theme, e.g. Arc or Adwaita:light." Restart Firefox.

Source:
https://github.com/DmitriK/darkContrast#text-contrast-for-dark-themes