The Firefox web browser comes with options to change the fonts used on websites that are displayed in its interface but there is no apparent option to change the font of the Firefox interface itself. It is possible to change the interface font, but that requires creating and editing the file userchrome.css in the Firefox profile directory, nothing that non-tech savvy users can do easily.
Theme Font and Size Changer is a Firefox add-on that offers to change the default Firefox font and size with a few mouse clicks.
The Firefox add-on adds an icon to the Firefox statusbar (or add-on bar if Firefox 4 is used). A left-click on the icon opens a simple menu with pulldown menus to change the Firefox font and size of the font.
The font listing is directly taken from the system font directory. Normal, which means default, options are available to make it easier to restore the default font settings of the browser if the need should arise.
The font change affects Firefox menus, toolbars, windows and other native graphical user interface elements. It does not affect the display of fonts on websites.
It is ideal for users who want to increase or decrease the font size and type of the interface because of specific requirements.
Visually impaired users can for instance increase the size of the font easily without changing the font type. This may also be helpful for widescreen users or users with high definition monitors.
The extension is not only compatible with the Firefox web browser, it is also compatible with the Mozilla email client.