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My question: is there a way to force a light TB theme and use white tab background text color?

I installed a theme add-on which I like except the associated dark theme. I want to use the theme image with a light TB theme but it appears the tab background text color determines the theme color (light or dark). This image has some darker colors and a light/white tab text looks the best, but this color seems to force a dark theme for the rest of TB (White text ->dark theme). If I change the manifest file to use a different tab background text color I can change the overall theme to light or dark. Using a darker or black tab background text color the theme changes to a light theme. Light tab background text color changes to a dark theme and darker tab background text colors forces a light them. I'm guessing there is a threshold 1/2 way between black and white text that will force the theme one way or another.

The articles I have read on this json file don't provide any examples and this is as far as I have been able to get. I'm new to both TB and modifying this json file. Any help would be appreciated

After upgrade Thunderbird to Nebula Almost all themes have the problem or the error that they change the design when I click on compose new mail, for example. And this design is unfortunately almost illegible. What can I do?

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

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 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.

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

I am trying to change my Theme and every time I enable a new theme, it changes for a minute but then it reverts back to the old theme that I can't even find anywhere in Thunderbird or on my computer. How do I get the new theme to "stick"?

As per my title, where can I find a themes toolbar background image and change it? I have tried looking for manifest.json and header.png files for the theme but I can't find it.

Or is there a way I can override it using CSS somewhere?

Windows 11

Cheers

GW

I recently updated to Firefox 135.0 on MacBook Pro, Catalina, OS 10.15.7 In the past, with multiple Firefox windows open & multiple tabs open in each, when restarting, "reopen pages on startup" selected, system loaded & ready to go, I'd find all windows, tabs & history available upon launching Firefox. Since update to 135.0, shut down & restart, launch Firefox and I find a single blank new window, no multiple windows, no tabs, no history. I've tried to find [Settings] to make everything come back - no joy, to no avail. Suggestions? Help? Thanks, JS

I have literally over 200 tabs open at a time and recover them every time I reboot Firefox, but they are very disorganized. Is there a good way to organize them, for example, group related tabs together?

I set a theme with https://addons.mozilla.org/en-US/fire.../firefox-color/(Firefox Color), I tried changing the theme in settings to light or dark but neither work. I'm wondering if there are other ways to do so in Firefox that I could try. I'm on zen browser which is why it may not have worked.

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?

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.