How to Enable Dark Theme in Mozilla Thunderbird

Mozilla Thunderbird is a very popular email client which is available for all the desktop platforms – Windows, Linux and macOS. Personally, I have been using it for more than a decade now and have never tried to use anything else. It works with all the different types of email servers including the private email servers and public email services like Gmail or Outlook.

Mozilla has already given an option to enable dark theme in the Firefox web browser. A similar option exists in Thunderbird. And here is how you can enable the Dark Theme in Thunderbird:

  1. Launch Thunderbird and press Alt key on your keyboard to make the menubar visible.
  2. From the menubar, select Tools → Add-ons to open Add-ons section.Dark Theme for Thunderbird
  3. Select Themes section from the left side.
  4. Click on the Enable button next to Dark Theme to enable it.Dark Theme for Thunderbird

If you want to turn off the dark theme anytime later, you can disable it in a similar manner. There is also light theme that comes built inside Thunderbird just like in Firefox. There is not need to restart Thunderbird, the dark theme is applied instantly.

Dark Theme for Thunderbird

The in-built Dark Theme does not make the Thunderbird interface completely dark or grey – it affects only the menubar, window frame, toolbar and buttons. If you want more darkness in Thunderbird user interface then you will have to use  a third-party theme called TT DeepDark. It gives a smoother and darker experience for Thunderbird. For this theme, you will have to restart the email client.

Dark Theme for Thunderbird

TT DeepDark really gives a very good dark them experience, and it looks much better than the built-in dark theme of Thunderbird. It even changes the graphics and icons for Thunderbird including the Thunderbird logo and “About Thunderbird” window.

You can download and install TT DeepDark extension for Thunderbird from

One comment

  1. Unfortunately TT DeepDark does not work on the newest version yet (7/22/2020). Your best bet in this case is the dark theme that comes with ThunderBird. You will also need to change the font and background color otherwise everything but the email reader box itself will be in dark mode. To do this go to:

    Options >> General >> Language & Appearance

    This may cause problems for some emails where the text color is specified in the email’s css. Choosing to display the email in “Simple HTML” will solve this problem:

    View >> Message Body As >> Simple HTML

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