Version 1 (modified by joshuadf, 10 years ago) (diff)


Editing Thunderbird userChrome.css

This follows instructions from the official Editing Thunderbird Configuration Files page.

  1. Find your profile, such as ~/Library/Thunderbird/Profiles/wxxrb45h.default/ or %AppData%\Thunderbird\Profiles\wxxrb45h.default\
  2. Create a subdirectory named chrome
  3. Create a text file named "userChrome.css" and add some CSS, for example:
    @namespace url("");
    /* Change the text color of unread messages to any color 
    *  of your liking - just change the hex value shown here. */
    treechildren::-moz-tree-cell-text(unread) {
    color: #0000CC !important;

The default CSS stylesheet is mailWindow1.css inside Thunderbird's classic.jar file, for example for unread messages:

treechildren::-moz-tree-cell-text(unread) {
  font-weight: bold;

You may want to look at the Mozilla Developer Center for more information on how Thunderbird (and Firefox) configuration files and extensions work.