Theme Font & Size Changer is a simple add-on that lets you change the font size and font family of Firefox and Thunderbird. It is especially valuable tool for visually impaired people and wide screen users.
There is four place that you can manage the global font size and font family of Firefox via Theme Font & Size Changer. Statusbar icon, toolbar button, Tools menu option and the Options dialog of the add-on. All font size and font family changes are instantly applied and they are saved permanently and through sessions.
Different from add-ons that enlarge and reduce text on web pages, Theme Font & Size Changer changes the font size and font family in all windows, menus, toolbars, etc within Firefox itself.
It was initially created to be an accessibility aid for persons with visual impairments and for those without perfect eyesight, but it's also useful for Firefox users with high monitor resolution settings and wide screens.
While Theme Font & Size Changer was written to be used with Firefox default theme, it does work with other non-default themes, but you may come across issues where some elements within Firefox retain the (non-default) font size setting that the theme developer chose for their theme.
There are 4 ways to access Theme Font & Size Changer settings panel:
1. Toolbar button (optional, not applied by default)
2. Status bar button (right or left click)
3. Tools > Theme Font Size Changer
4. Tools > Add-ons Manager > Theme Font & Size Changer > Options
In Theme Font & Size Changer settings panel, Font section provides fonts currently installed on your operating system. With this option set, you will be able to fine tune your font family of Firefox theme.
In Size section, simply select a font size value (from 6 to 80 pixels) and the changes will be applied instantly and globally.
A Normal (default) value is also provided as well as an indicator next to the currently applied font size and font family setting so that you can reset to the default Firefox values.
How to Install in Thunderbird:
1. Right-click the link below and choose "Save Link As..." to download and save the file to your hard disk.
2. In Mozilla Thunderbird, open Add-ons from the Tools menu.
3. Click the Install button, and locate/select the file you downloaded and click "OK".