Firefox looks like Windows firefox in (system-wide) light mode, but follows gtk3 theme in dark mode

This is what Firefox looks like in dark mode. (with “system/auto” theme selected in preferences and GNOME in dark mode). This is the default Adwaita gtk3 theme.

Firefox on windows (or on Fedora with “dark” theme selected in Firefox preferences ) looks like this. Notice the address bar and tabs area.

However, this inconsistency does not arise when using the light theme… although it did exist at some version of Firefox (the one which you get on a fresh install of Fedora 39 before a dnf upgrade). Firefox just uses it’s Windows look (or how it would look when locked to “light” theme from Firefox preferences) when “system/auto” theme is set in Firefox preferences and GNOME is in light mode… This is not the default Adwaita gtk3 theme.

However(!), Firefox does follow adw-gtk3 theme if set from gnome-tweaks, both in light and dark mode.

I do not think this is intended behavior. Is there a way I can make Firefox look like it does on Windows both in light and dark mode? Here, by light and dark mode I mean light and dark setting of GNOME, with the “system/auto” theme selected in Firefox preferences (because I want Firefox to switch light/dark mode in sync with the rest of the GUI without extra steps).

Fedora version: 39
GNOME version : 45.4
Firefox version: 123.0.1 (problem exists both on rpm and Flathub variants)

Gnome-tweaks dos exactly what the name suggests, it tweaks gnome.

Sometimes it is quite difficult to do some settings in Gnome or the default settings app not let you make this changes. That is why gnome-tweaks exists.

There are also gnome specific themes for Firefox. You might give this a try.

Do not forget that Windows isn’t Linux. So slight differences always will exist.

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I think my question was not clear. What I’m asking for is basically this:

  • Firefox ignores gtk3 theme (Adwaita) in light mode but follows it in dark mode.
  • I want firefox to ignore the gtk3 theme in dark mode as well.
  • Or alternatively, just follow the gtk3 theme in light mode. I want a consistent appearance

This has nothing to do with Windows or Gnome and the problem is (probably) with firefox and how it handles theming. I gave the example of firefox’s appearance on windows because that is what firefox looks like when it ignores the gtk3 theme, or when you manually select a light or a dark theme from firefox preferences as the gtk3 theme is used only when firefox theme is set to “system/auto”.

Repeating myself, this inconsistency that I mention was not present in an earlier version of firefox (the one that you get pre-installed on a fresh install of Fedora 39 before running dnf upgrade). It has been introduced by an update (can’t pinpoint which one).

This should probably be reported as a bug against firefox if the behavior change you report is repeatable. Are you using the flatpak or the default rpm version of firefox?

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Problem exists on both rpm and Flathub variants.

Lately we had the change from gtk3 to gtk4. So if you have a older version of Fedora updated you might also have to assure, that the gtk4.css is present in the theming. Otherwise such a missing config can exist and not display correctly as you wish.

So before you ask “I want a consistent appearance” you also have to give enough information that someone is able to reconstruct your problem and if needed, can tell you what you have to fix alias to make a bug-request to remove the issue.

It is quite difficult for us to when you not give more info how your setup looks like. Have you tried to boot with an older kernel to see if you can see a difference ?

I don’t understand what difference in behavior you see between Firefox in light mode and Firefox in dark mode. In either case, it uses its standard theme with colors that match the GTK3 Adwaita color scheme.

You understand that Firefox is not a GTK app, right? If you want to match GTK4/Libadwaita more-or-less exactly, you can use the Firefox GNOME Theme.

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So you mean Firefox now uses gtk4 instead of gtk3 themes? Thanks, this is new information for me. I’ll look into it.

This is a fresh install of Fedora so I know for a fact that there are no configs that are interfering… unless they were put there by Fedora at install time, which is also not the case. (I know this because Firefox on a fresh install of Arch Linux behaves the same)

Pretty sure this behavior will occur on any fresh install of Fedora. I recently installed Arch Linux to try out the new release of KDE Plasma and this behavior was same in Arch Linux’s Firefox as well.

My setup is precisely this:

  1. Install Fedora 39. → no problem at this point
  2. sudo dnf upgrade → problem arises
  3. flatpak install flathub org.mozilla.firefox
  4. flatpak upgrade → problem is same in flatpak variant as well

What does the kernel have to do with this? By “update”, I mean a firefox update created this isssue.

Please look at the two screenshots for dark mode again. The first one shows what it looks like when using gtk theming, the second one shows how it should look without gtk3 theming.

The screenshot for light mode is not using gtk3 Adwaita theme. This is how firefox looks without gtk theming and this is how it looks on Windows.

Yes, Firefox is not a GTK app and I do not want FIrefox to pretend to look like one. From what I know, Firefox had been going out of their way all these years to follow gtk3 theming on Linux and that is the reason why it looked different from the Windows release which uses Firefox’s default color scheme. I want Firefox to follow it’s default color scheme (which it does in light mode, but not in dark mode) and not try to imitate the gtk3 theme. Or, alternatively just use the gtk theme both in light and dark mode but I would prefer the former adjustment.

I think you’re mistaken. “System theme – auto” always uses GTK colors, in both light and dark mode. The “Light” theme is different, even if the difference is more subtle than with “Dark”. “System theme” (light mode) is a distinctly warmer shade of gray than “Light” (which is the only variation you didn’t screenshot).

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Yes. I was mistaken. On older versions of firefox the difference was more pronunced which led me to believe that firefox stopped using the gtk theme and used it’s default colors instead. Now that you pointed it out, I see the difference between the inbuilt light theme and the gtk light theme. Thanks! (and sorry for wasting your time)

Turns out my question was for nothing. Should I delete this thread or let it be?

Threads should never be deleted.
Only mark the proper post as the solution and move on.

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