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DeepDark | Amethyst Edition (addon for Thunderbird 68)

: : : ! IMPORTANT ! : : :

BEFORE installing this add-on, please:

- Disable any theme that you previously installed (to prevent UI visual issues);

- Disable other similar add-ons (this is also valid if you have a DeepDark special edition add-on already installed) and RESTART Thunderbird;

- If you have an older version of DeepDark installed, remove it and RESTART Thunderbird;

- If you already make use of custom “userChrome.css” and “userContent.css”, be aware that the content of these files may create conflict(s) with DeepDark add-on by overriding its code;

- Make sure that you DON’T have the “light” Thunderbird default theme enabled;




"DeepDark | Amethyst Edition" is an add-on (derived from my original "DeepDark" add-on for Thunderbird) created to transform the look and feel of Mozilla Thunderbird*. It has been specially designed to work with Thunderbird on the following operating systems**:

- Windows 10 (10.0.18363 build 18363);
- MacOS 10.14.6 (Mojave);
- Linux Ubuntu 18.04.1 LTS (Bionic Beaver).

This add-on doesn’t add specific functionalities to the Thunderbird software. It focuses on providing a full GUI (Graphic User Interface) aesthetic customization by replacing colors, icons and, in some cases, by changing the spacing around UI elements and/or their position.

This add-on also styles "Lightning" which is a calendar add-on (created by Mozilla) frequently used together with Thunderbird.

The received emails and message compositor areas' appearance is not modified by this add-on (users already have the possibility to customize these areas' colors thanks to the default Thunderbird options).

!Important! You may use this add-on on a personal, non-commercial basis only. For more information, please, check the "README_LICENSE.txt" file included inside the add-on's package.

*Mozilla Thunderbird is a free, open-source and cross-platform email, news, RSS and chat client developed by the Mozilla Foundation.

**Please note that if you install the add-on on other operating systems than the one mentioned above, I do not offer support for them. This is also valid if you use an older version of an operating systems listed on this page.

Note: I am not affiliate with the Mozilla Foundation.



Version: 1.0.11
Last update: Aug 27, 2020
Works with: Thunderbird 68.*



"DeepDark | Amethyst Edition" was created for all those who would like to use a different color variation of my original add-on and, at same time, to support me in keeping alive and expanding my self-initiated project called "DeepDark", which aims to develop/maintain a "Suite" of dark themes/skins for a wide range of popular softwares.



If you don't know yet how to install downloaded Thunderbird add-ons, please head to the official Mozilla support site. There, you will find detailed informations to help you how to do it.



1) Extract the "" file content and keep the folder named "chrome" in a location that you will easily remember (you will need this folder later);

2) Open Thunderbird, click the menu button, then "help" and finally "Troubleshooting information";

3) Once that the "Troubleshooting information" page is open, look for the "Profile Folder" row in the first table and click the button next to it which says "open folder" (on Windows), "Show in Finder" (on Mac) or "Open Directory" (on Linux). This will launch a new window with your system's file browser.
In the new window that you just opened, on Windows and Linux, you will be able to directly see your "profile folder" content. On Mac, if the "Finder" shows you a semi-randomly-named folder, double-click that folder so you could access its contents;

4) Copy or move the "chrome" folder (previously extracted) into your Thunderbird profile folder;

5) Restart Thunderbird and you are done!

The "chrome" folder that I included with my add-on contains few CSS files which will help to customize areas that I couldn't directly style through my add-on. It will bring the following extra-customizations:

- Thin scrollbars (for Windows and Linux users);
- Dark scrollbars for the messages content area (for Windows and Linux users);
- Dark styling for the Thunderbird: start page, error console, multi-message view and discovery pane.

The userstyle concretely works as described below:

At startup Thunderbird always checks for the presence of "userChrome.css" and "userContent.css" files in a particular location: a folder named "chrome" inside your currently active profile folder (all of your current settings and add-ons are stored in there). So by adding in your profile folder the "chrome" folder that I provided together with my add-on, your Thunderbird will read and apply the CSS code it contains.

For more information, you can head to



1) Before reporting it, first try to see if the issue is due to the add-on itself. How ? Disable the add-on, restart Thunderbird and check if the issue is still there. If not, enable again DeepDark, but disable all other installed add-ons (restart Thunderbird again) to check if the issue can be due to a conflict between add-ons.

2) If the issue is still there after disabling all other add-ons and if the default Thunderbird theme doesn't have it, try to install again DeepDark (check also if you have the latest version installed, maybe the bug you want to report was already solved with the latest update).

3) If after trying what mentioned above the problem is linked with the use of DeepDark, please, send me an e-mail (you can find it on my website).

When sending an e-mail to report a bug, do not forget to tell me:

- Which operating system you are running on your computer;
- Which version of Thunderbird and DeepDark you are using;
- If you have any operating system custom theme installed (it can also be a cause of the issue).

Then, describe the most precisely you can the issue you are facing and, if possible, please, join a screenshot and/or a short video so I could see exactly how it looks. All that will help me to better understand what is the problem and to solve it quicker, if possible.

I can t promise that I ll manage to fix every problems and also in short time, but I ll do my best for it. I m working on my add-ons during my free time so it can take a bit time before fixing the issues.

You will get the following files:

  • ZIP (179KB)
  • XPI (534KB)

$ 2.90

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(minimum $2.90)

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