You can change this pref on the about:config page from 3 to 2 to revert to the Firefox 94 behavior.

• layout.css.prefers-color-scheme.content-override [dark:0, light:1, system:2, browser:3]

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

See also these prefs:

• ui.systemUsesDarkTheme [light:0, dark:1, no-preference:2]

The theme I am using has not been updated in 2 years so I am fairly sure the update has caused this.

You are correct!

What is happening in Firefox 96

Firefox 96 now harmonizes more parts of Firefox with your toolbar theme. When the text color on your background tabs is light/white, it triggers Firefox to use a dark background on menus, the sidebar, the Library window, and various built-in pages. Firefox also signals sites that you have a dark theme preference.

(I realize that many users consider their toolbar theme purely decorative and don't want Firefox to use it to drive colors in other parts of the browser. We are hoping that eventually there's a checkbox for this on the Settings page, but that probably is some time away.)

What to do about this now

(1) For people willing to change their toolbar theme

The fastest workaround for now is to change your theme to one that uses dark text. By dark text I mean, for example, the built-in Light theme, or an add-on theme with black or dark text on the tabs. That doesn't need to be blinding, it can have a pastel color. As examples:

• Firefox Logo: https://addons.mozilla.org/firefox/addon/firefox-b/
• Winter snow: https://addons.mozilla.org/firefox/addon/blue-winter-snow/
• Green shoots: https://addons.mozilla.org/firefox/addon/printania/
• Great wave: https://addons.mozilla.org/firefox/addon/japan-style-kanagawa-gr-232767/
• Kitten: https://addons.mozilla.org/firefox/addon/savage-black-kitten/

I have attached a screenshot illustrating the difference between a theme with light text on the tabs and dark text on the tabs.

(2) For people who can't part with their toolbar theme

As cor-el mentioned, there is a partial workaround for the built-in pages, and for websites that have light/dark responsive themes. (This is the middle panel of the attached screenshot.)

Currently, the only way to decouple your page (content) theme preference from your toolbar theme is through the back door:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button accepting the risk.

More info on about:config: Configuration Editor for Firefox. The moderators would like us to remind you that changes made through this back door aren't fully supported and aren't guaranteed to continue working in the future.

(2) In the search box in the page, type or paste layout.css.prefers-color-scheme.content-override and pause while the list is filtered

(3) Double-click the preference to display an editing field, and change the value to whatever you prefer from the list below, then press Enter or click the blue check mark button to save the change.

• 0 => Force a Dark background
• 1 => Force a Light background
• 2 => Follow the System theme (default in Firefox 94)
• 3 => Follow the Browser toolbar theme (default in Firefox 95+)

The about:config page should immediately reflect your saved change.

What about other aspects of the UI?

For the sidebar, menus, and toolbar drop-down panels, there is an unofficial, community-supported option, which is to override the built-in styles using your own style rules in a userChrome.css file. I think people are still pondering how to do that efficiently, and perhaps you aren't that into hacking your browser anyway.

Thanks for that Jscher2000.

I've followed your second option and changed the config, google and youtube now have the white background and are much easier for me to read.

I could have changed the theme easily, but I like to keep things the same as much as possible as I'm easily confused for various reasons.

Many thanks again

Just to say I used jscher2000's solution with the about:config and it worked a treat! (even if it might get overridden in the future, but I just hate to wake up to see just all layout has been changed for no good reason.) Thanks jscher2000!!

Firefox 96 now harmonizes more parts of Firefox with your toolbar theme. When the text color on your background tabs is light/white, it triggers Firefox to use a dark background on menus, the sidebar, the Library window, and various built-in pages. Firefox also signals sites that you have a dark theme preference. </blockquote>

Thanks for the information, but what the fuck was Mozilla thinking implementing this (aka forcing it on the users) without giving us a simple option to turn this stupid behavior off? I'd rather not say what I think about this because it might go against the community guidelines. This needs to be fixed ASAP

Hello Firefox-Deveolopers / Mozilla: If you keep doing those kind of abrupt changes that are supposed to be improvements but pisses off many users, your market share will still decline further to zero.

This is sickening. I'm starting to look for alternatives right now.

I want to disable dark theme--permanently. I don't like dark themes because they hurt my eyes and are annoying to look at. I don't know why your developers took it upon themselves to decide that us users would like dark backgrounds. Even theme creators don't like their themes being forced into dark mode. Users don't have a choice to toggle it off. I don't want my location bar to be black...ever; I don't want menu dropdowns and new open tabs to be black. I shouldn't have to click around looking around for and trying out themes to avoid this issue. I have several favorite themes saved and they're ruined because different aspects have white font on a black background. I shouldn't need to fiddle around with config either. **Just make a toggle in the settings/preferences and give us customers what we're telling you we want and don't want**. This type of stuff really pisses customers off. Too many developers everywhere break things that didn't need fixing. For now, I'm going to stick with Dissenter browser; it's much cooler anyway, and protects our privacy. Firefox is squirrely and too many updates, almost daily. Send a notice when you fix this dark theme annoyance by adding a toggle/check box etc., and maybe I'll take a look at Firefox again.

I want to echo a big TY! I can see again!

I like my themes, but leave the rest alone!! I have my setting the way I want them, not nice to force change.

I've been trying out different browsers because FF is just going so down the tubes with their "new" ideas. So much for the simple awesome browser that was, buh-bye!

This keeps me happy for a bit longer, YAY!

or not...couple hours later, its back.  :(

Thank yous to everyone trying to help with this very trying problem.

I would like to try using this--ui.systemUsesDarkTheme [light:0, dark:1, no-preference:2]-- but not sure what it is, where to find it or how to add it, & how to select light theme once I find or add it!

I would like to try using this--ui.systemUsesDarkTheme [light:0, dark:1, no-preference:2]-- but not sure what it is, where to find it or how to add it, & how to select light theme once I find or add it!

I'm not sure that one has any effect these days, but here is an old thread with the detailed steps to create that preference if you want to try it:

https://support.mozilla.org/en-US/questions/1326935#answer-1394154

More recently, a user mentioned having to delete it: https://support.mozilla.org/questions/1339400