How To Increase Thunderbird Line Height

I’m a long time user of the Thunderbird email client. It is very robust, easy to use and the mail-filtering system is top-notch. Recently, I learned that you can increase the line height to improve readability. By default, messages and folders are quite close to each other which makes readability a bit difficult. In this article, I will share with you how I increased the line height in Mozilla Thunderbird.

Modifying the userChrome.css

To modify the user interface in Thunderbird, one must edit the userChrome.css in <your-thunderbird-profile>/chrome/userChrome.css. At the time of writing this tutorial, I am using Mozilla Thunderbird v60.8 however it should work for older versions as well.

On Linux, navigate to the following folder:

cd ~/.thunderbird/<your-thunderbird-profile>/chrome/

On Windows:

  1. Press WIN + R, type %appdata% and press enter.
  2. Now navigate into the following folder: Roaming\Thunderbird\Profiles\<your-thunderbird-profile>\chrome\

NOTE: If you do not have a chrome folder, create one.

Now create the file: userChrome.css (case-sensitive) and paste the following into the file:

/* Row Height*/ treechildren::-moz-tree-row {
   margin-top: 2px !important;
   margin-bottom: 2px !important;

That’s it, now launch Thunderbird and enjoy the improved readability. If you wish to increase the padding more, simply change the margin-top: and margin-bottom: pixel values.

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