userChrome.css and .js and userContent are unsupported

Revision Information
  • Revision id: 263923
  • Created:
  • Creator: Roland Tanglao
  • Comment: edits as per Wayne's feedback.
  • Reviewed: Yes
  • Reviewed:
  • Reviewed by: rtanglao
  • Is approved? Yes
  • Is current revision? No
  • Ready for localization: Yes
  • Readied for localization:
  • Readied for localization by: rtanglao
Revision Source
Revision Content

userChrome.css is a CSS style sheet that allows developers make changes to Thunderbird’s user interface. The CSS rules in userChrome.css are applied to the user interface, and can override nearly every built-in style rule. userChrome.js allows anyone to inject Javascript code that changes Thunderbird. userContent.css and userContent.js are similar features for websites.

userChrome.css, userChrome.js, userContent.css and userUContent.js are very powerful tools, intended for testing by technical users who are familiar with JS, CSS and HTML. The Thunderbird Project does not offer support for modifications to these files. This is because Thunderbird developers are constantly making improvements to the HTML elements which alters the CSS selectors as well as the underlying Javascript code. These changes mean that customizations based on userChrome.js, userChrome.css, userContent.js and userContent.css can break Thunderbird at any time and are very difficult to troubleshoot.