Themes let you customize the appearance of your Firefox. You can add background images to the header of your browser or change the colors of various components like the URL bar or the tab text. It’s easy to create themes using the theme wizard on addons.mozilla.org or Firefox Color.
To get started, check out the Themes section of Firefox Extension Workshop. The site offers a tutorial for using the theme wizard and instructions for coding your own theme. We’ve also added information about how to update themes using the theme wizard or by submitting a new file package.