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.

The Firefox add-on is compatible with all Firefox versions from 3 to the latest Firefox 4 builds. Thunderbird users can download the extension from here.

Hacking the style files on the other hand is not something that every user can do nor wants to do. That’s where add-ons like Theme Font Size Changer comes into play. Add-ons are another – more convenient – way of changing Firefox elements and styles.

This particular add-on changes the font size of the Firefox theme. Firefox theme in this regard means all interface elements that display text including tabs, menus, status bar, address bar and other toolbars and even the context menu of the browser.

The add-on places an icon in the Firefox status bar that will open the font size selection menu when pressed. Selecting a new font size will instantly change the size of all Firefox interface elements to the selected size.

The font size selector offers one entry to reset the font size to the normal one used in Firefox by default. This is helpful in case the changes turn out to make interface elements inaccessible or unreadable.

Theme Font Size Changer can be downloaded from the official Mozilla Firefox add-on repository.

The Make Font Size Bigger Pack is a Firefox add-on that will automatically increase the font size of the fonts in the Firefox address bar, tab bar and status bar. The new font sizes are automatically enabled after installation of the add-on and a restart of the web browser.

The pack combines two add-ons of the same developer in one add-on. Firefox users can also download the Make Address Bar Bigger and Make Tab Bar And Status Bar Bigger add-ons instead in case they only need one of those.

There are no configuration options currently but the developer promises to update the add-on soon with options to edit the font size and an option to enable or disable the add-on in the Firefox web browser.

Firefox users who prefer to change the font sizes, colors and fonts in general can edit the userchrome.css file directly which is located in the chrome directory of the Firefox profile folder. It can be that only a userchrome-example.css is available, just remove the -example part from the url in that case.

/*Change address bar font, color and size*/
#urlbar {-moz-appearance: none !important;
font-family: Tahoma Bold !important;
color: Black !important;
font-size: 12pt !important; }

The above code changes the font of the address bar to Tahoma Bold with a font size of 12pt and the black color. Just replace the values with others if you prefer those.

/* Change status bar text color/size*/
#status-bar {-moz-appearance: none !important; font: bold 12pt Arial; !important;
}

The code above changes the font of the status bar to 12pt Arial.

/* Active tab - good */
.tabbrowser-tab[selected="true"]
.tabs-bottom,
[class="close-button tabs-closebutton"] {
font-weight: bold !important;
background-color: rgb(220,220,220) !important;
padding-left: 2% !important;
padding-right: 2% !important;}

/* Inactive Tab - good */
.tabbrowser-tab:not([selected="true"]) {
-moz-appearance: none !important;}

The code above puts more weight to the active tab. You can modify the fonts as well using the examples above.

Update: The add-ons have been discontinued. A new add-on is available that offers a similar functionality. Theme Font & Size Changer is available for direct installation over at the Mozilla website.

Lifehacker have an article up on their website detailing the process of switching from the default fonts used by most websites and the computer system to the Vista fonts. This is easier done than one would think. A user who wants to enable those fonts in the Firefox web browser needs to have a working installation of Microsoft PowerPoint 2007, Microsoft Office 2007 or the free Microsoft PowerPoint Viewer 2007. This ensures that the Vista fonts are installed on the computer system. Vista users do not need to perform this operation since their operating system ships with those fonts.

The next step involves switching to ClearType if the computer is connected to an LCD monitor. This can be done with a powertoy from Microsoft.

It is then time to configure Firefox to use the Vista fonts instead of the default fonts after installation of the fonts and enabling ClearType. This is done in the Tools > Options > Content menu. A click on the advanced button under Fonts & Colors will display the following configuration menu. Just switch to the same fonts and settings that are shown in the following image:

It is important to uncheck the checkbox at the bottom to prevent pages from selecting the fonts. The result can be a better readability and is something worth to try.