Firefox Community Forum

I have a custom theme enabled on my browser. Every time I log into Firefox on a shared university computer my theme is turned off for that desktop aswell as my personal laptop. I have to manually enable it on my personal devises again each time after using school computers. Is there a way to prevent this?

I have installed an animated theme for my home page a while back, but recently if I minimize firefox the memory usage increases until it freezes my pc completely. I know this issue has been reported as Bug 1828587 2 years ago and it is said that it is fixed, but here I am experiencing the same thing. I would appreciate any help since I am not that good at coding a css file. Here is my userContent.css code if maybe i set something up wrong:

@-moz-document url("about:newtab"), url("about:home"), url(about:privatebrowsing) {

   /* Sets background image and autoscale image to browser window. */
   body {
       background-image: url("wallpapers/wallpaper.avif") !important;
       background-size: cover !important;
       background-repeat: no-repeat !important;
       background-attachment: fixed !important;
       background-position-x: center !important;
       background-position-y: bottom !important;
   }

   @-moz-document url("about:newtab"), url("about:home") {
       .top-site-outer .title {
           color: white !important;
       }

       .logo-and-wordmark .wordmark {
           fill: white !important;
           color: #00aaff !important; /* fallback for text */
       }

       .context-menu-button.icon {
           fill: white !important; /* for SVG-based icons */
           color: white !important; /* for any text-based fallback */
           opacity: 1 !important; /* ensure visible even when normally dimmed */
       }
   }

The second part is to make some of the text on my homepage white so it is visible.

When I updated to Firefox 146 yesterday, the theme I was using disappeared and I ended up making a new theme using Firefox Color. I submitted it to the add-ons list and it has now been accepted, so now I am using it installed from the add-ons. Ever since I started using the new theme, even before installing it from the add-ons menu, my private browsing window is also using that theme. I want private browsing to use the default dark theme. That way I can easily tell if I'm using the private window or the regular Firefox window. However, I can't find a way to change a setting to go back to the dark window for private browsing. I've already checked about:config and browser.theme.dark-private-windows is set to true. I even toggled it to false and then back to true but there is no change. I looked at the settings for the extension Firefox Color, and it is turned off for private windows. I looked at the settings under the theme add-ons, but I don't see a setting there to turn it on or off for private windows. Am I missing something?

I am now on the very latest version, 146.0.1, and my private browsing window is still using the same theme as my regular window.

As above themes not working on latest version of firefox difficulty reading menu & tabs bar as light blue needs to be dark coloured

Also have difficulty reading your website because of white background will not work on dark mode retinopathy burn

As of 12/9/25, Firefox seems to now prevent Theme add-ons from working if there is a contrast setting configured in Windows configuration. (Version 146.0) Previously, this allowed a very aesthetically pleasing view. I would greatly enjoy having that option again. Thank you.

Turns out you cant use your own stuff until it is approved, Sorry for this question I am absolutely new to firefox workshop. Case closed (Please delete it because I couldn't find how to do that)

I encountered an issue when exporting a theme from Firefox Color. When I downloaded the XPI file, it contained only a `manifest.json` and **did not include the background image files** referenced in the manifest. This caused Firefox to reject the theme as “corrupt” when trying to install or import it.

What I discovered during debugging:

1. Firefox Color provides both a **ZIP** and an **XPI** download.

  The ZIP contains the correct folder structure and the background image files.
  The XPI is missing these files entirely.

2. Because the XPI is missing required assets, Firefox treats the file as corrupt.

3. Importing the broken XPI through the Add-ons Manager or uploading it to AMO also triggers corruption or validation errors.

4. I had to manually inspect the ZIP, extract the proper `images/` directory, and rebuild the XPI myself.

5. I ended up using ChatGPT to troubleshoot the issue, confirm expected manifest structure, correct extension ID mismatches, and verify JSON formatting.

The issue appears to be that Firefox Color’s **XPI exporter is broken or incomplete**, producing theme packages that cannot be installed or validated without manual repair.

It would be helpful if Firefox Color’s XPI export included all necessary files consistently and matched the structure found in the ZIP download.

Hello!

SECERITY: LOW, COSMETIC DESCR.: I love how many yhere are beautiful themes for ff. I Like to install any the I think is beautiful and keep enjoing all of them by switching them to see it on FF itself. Now - not aftyer every change of active theme, but after a few/scrooling the order of the Themes on list is re-sorted. It is a little trouble for me as I like to chnge/watch them afew times a day (like person who like to watch theirs clothes, how their look in that clothes, so they keep changing them and see how they look in the mirror). So Id like the list of themes to be fixed, so I can go throuh the whole list and make sure I didn't missed any of my installed themes. OK, I hope I manage to explain it. I'm 40+ yo soft dev. so you can ask me technicall questions. And also: a setting among about:config to change this list behavior whould be absolutely enough solution for me.

Best regards, Michał Dąbrowski

i am unable to see my installed themes and therefore can not use them. the only thing that i can see is "extensions" and "plugins". i looked online for a few hours and have found no solutions that work.

Hi, I rebooted Firefox today because a website was frozen, and when it came back, it was asking for a troubleshoot or just continue, and I don't know exactly what that meant, but when I clicked on refresh, everything was changed, including the theme. And then when I tried to restore the theme back to the original it said, add-ons are disabled by safety, and I don't know what that means, and it's not explaining how to undo it. And now everything looks different and I'm not happy with it, and it's not really letting me add any other themes, and if I add them, they don't seem to fully load, the page still looks all white

Dear Mozilla Support Team,

I am writing to report an issue I have consistently encountered while using the Firefox browser. Whenever I log into my Mozilla account, the custom theme I have selected for Firefox is reset to the default theme. This necessitates manually re-selecting my preferred theme each time I log in.

This issue is a minor inconvenience, but it disrupts my user experience. I would appreciate it if you could investigate this behavior. I am using the latest version of Firefox on Windows 11 Pro.

Thank you for your time and attention to this matter. I look forward to a resolution.

Sincerely,

Clóvis Lauriano [edited email from public]

Best regards,

At the beginning of 2025, I created a private theme and installed it locally (Windows 10), consisting of a manifest.json and a GIF file. It worked perfectly. Now, on Windows 11, I'm trying to use the theme again, but when I upload the file (.zip or .xpi — via about:addons -> Install Add-on From File), I always get the message that the file is corrupted. However, if I test it temporarily under about:debugging, it works immediately without any issues.

I would really appreciate a solution! <3

I’m at my wits’ end with this. Firefox keeps forcing a system-synced theme at launch, and it flat-out refuses to respect the settings I’ve configured — both in about:config and via a custom user.js file.

Here’s what I’ve tried:

• Set layout.css.prefers-color-scheme.content-override to 0 in about:config → it reverts back to 2 after every restart.

• Created a user.js with user_pref("layout.css.prefers-color-scheme.content-override", 0); → completely ignored.

• Disabled all sync options, including themes.

• Verified that no active studies are interfering.

• Double-checked that I’m not syncing across devices.

• Tried applying a specific theme and setting it manually — still overridden at launch.

No matter what I do, Firefox insists on syncing the theme to the system’s dark/light setting. I want my browser theme independent from the OS — period.

Is there a deeper setting I’m missing? A hidden override? Some service that’s reapplying the system setting post-launch? This feels like Firefox is actively fighting me — and it's infuriating.

Would appreciate any insight or workaround. I just want full manual control over my theme. Why is that so hard?