Firefox dark mode not working

Firefox browser started normally recognizes windows dark mode and firefox chrome becomes dark. When started in sandbox, firefox is normal, bright. Sandboxed firefox apparently can not read some windows property telling that windows is in dark mode. This started with firefox 68 just recently. Firefox behaved correctly.

Environment: firefox 68, windows 10 enterprise 64 dark, empty sandbox, sandboxie 5.31.2 64.

  • Hi bob,

    Did you delete the contents of your Sandbox prior to launching Firefox after changing the theme? I tested it and everything is fine, except for the top part which is still white.

    Unfortunately, the white bar at the top is a known issue when using Windows 10 and Firefox and it is related to the way Windows 10 manages themes. I don't have access to the old threads, but the suggestions varied from changing the theme, to changing Sandboxie's appearance settings (Right-click on your Sandbox --> Sandbox settings--> appearance) , for most users, finding a new theme did the trick. 


  • In reply to Barb@Sophos:

    As I have written, the sandbox was empty. I have emptied it just before running firefox. And I did not change the theme. I expected default theme to adapt itself automatically.

    The issue I report is not about dark theme not working at all in itself. I can have dark firefox, when I explicitly enable dark theme (and I just do it now). My issue is, that firefox can not automatically adapt itself to windows dark/white setting on default theme, which it did do correctly just until now. Now (apparently) firefox devs changed the way firefox tests for dark/bright windows, and this presumably new way is blocked by sandboxie. This blocking is my issue.

    And as to reproducing the problem: I have tested it on another computer with older version of windows, 1803, and behavior of sandboxed firefox 68.0 was that same wrong.

  • In reply to bob foormanek:

    Hi bob,

    Thanks for your response. 

    Can you please walk me thru the steps to repro the issue, and if possible, include a screenshot of what are you seeing (and what do you see in the host)? 


  • In reply to Barb@Sophos:

    On desktop I have firefox icon installed by default. I double click it and run firefox in default-release profile, which is untouched by me at all (I use profiles). Firefox starts and it is dark.

    I close firefox, empty the sandbox, right click the firefox icon and choose "run sandboxed". Firefox asks for profile, I choose the same as above, and it starts as bright.

    Golden top you see is my chosen windows accent color. Dark grey around is my desktop solid background color.

    Firefox is on factory settings with default theme active. Default theme should adapt itself to windows dark/bright settings.

    My windows edition is:

  • In reply to bob foormanek:

    Hi bob,

    Thank you, I was able to replicate the scenario with your steps. Seems related to previous issues with Firefox and different themes + Windows 10 and the way they handle colors, themes, etc.

    As a suggestion, enable Firefox' dark theme (it will most likely produce a white bar at the top, but everything else should look okay) and see if that allows Firefox to turn to dark mode.
    Firefox options --> Addons --> Themes . Locate "Dark" and enable it. Then re-test launching FF in the sandbox to see if that helps a bit. 

    I'll let you know if I receive any new info from the devs about this.


  • In reply to Barb@Sophos:

    As I wrote in my first reply, dark theme as such works, with a white band on top when the windows is unfocused, and having no other choice I use this method now.

    If you could solve automatic dark/bright switch in default theme though, then probably other issues with firefox colors would go away as well, because all this seems related.

  • In reply to bob foormanek:

    Hi, I apologise but I'll steal this thread since I think this issue could be related to OP's problem.


    I use Firefox with Sandboxie on a Windows 10 x64 PC. Sandboxie is v5.31.2 and the problem started right after I upgraded Firefox to the latest version, which is Firefox v68.0.


    What I experience is this:

    What is the problem? If I run Firefox outside of the sandbox, it displays normal (thin) text on the tabs. If I run Firefox sandboxed, it displays the tabs that are not selected with weird bolded text. This sometimes applies to the menus too, it's weird.


    Any idea how to get rid of that bold text and have it like it was before, with the previous versions of Firefox under Sandboxie?

  • In reply to Bellzemos:

    Hi Bellzemos,

    As covered, this is not a new issue, comes and goes with different versions of Firefox.

    You can try using a different theme, or the suggestions I provided on my previous responses to see if any work for you.

    I'll update this thread if new info becomes available.