How to increase the font-size in Thunderbird Mail

How to increase the font-size in Thunderbird Mail

As an dedicated Linux user I am using Mozilla Thunderbird as mail client. In this contribution I explain how you can increase the font-size of the mail list with use of CSS

As an dedicated Linux user I am using Mozilla Thunderbird as mail client, but since I have my mail on my laptop as an extra display I have hard time reading it from a distance, since I am doing the main work on my external display.

The only thing I needed is an increase of the font size of the list of mails. In this short contribution I will tell you the quickest way to get it done.

Step 1. go to your profile

In the ~/.thunderbird folder you will find a file named profiles.ini. Open that file and see what profile folder you need. It looks something like dekz1s3k.default-release, but then with your own prefix.

Step 2. create the required css

  • When in the ~/.thunderbird folder no folder exists named chrome, create this folder.
  • Create a file in the chrome folder named userChrome.css and enter the following contents:

 * Do not remove the @namespace line -- it's required for correct functioning
@namespace url(""); /* set default namespace to XUL */

 * Make all the default font sizes 20 pt:
* {
font-size: 20px !important

Save this file and restart Thunderbird Mail. You can modify the font-size to your own taste. But after every modification don't forget to restart Thunderbird.

Useful links

1 year ago
Hi Johan
Thanks for your effort.
I have one remark and one question
1) Remark
the chrome folder should be within thunderbirds profile folder
(dekz1s3k.default-release in your example)

2) Question
As far as I can see, one can set these fonts within TB (68.10 on focal fossa) directly
I couldn't how to set the fontsize of the message body.
If you happen to know that, I am curious to hear from you


8 months ago

Thunderbird Configuration files

seems to have moved.

Do you k now where it is now?
Well that page seems gone for good. You can find a hard-copy of this page here (archived): link to archived page

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