How to change the font size in the Firefox address bar

I started using Firefox ages ago because I believed it to be safer than Internet Explorer (think ActiveX and BHOs). Over time, I've gotten spoiled by the customization that it offers, another huge advantage that Firefox has over IE.

While IE turns the address bar green on websites that use Extended Validation certificates, Firefox can be made to display a green address bar (a.k.a. awesome bar and urlbar) on all secure (HTTPS) web pages. I find this an invaluable visual aide, and blogged about it back in February.

Yesterday, I met with a Firefox user with poor vision. This person was well schooled in using Control-Plus and Control-Minus to adjust the font size on web pages, but they were still left with a problem - the address bar. Control-Plus only increases the text size on a web page, it does nothing about the address bar.


Firefox lets you specify a minimum font size (Tools -> Options -> Content tab -> Fonts and Colors -> Advanced button in Firefox 3.5.2) but that too, only applies to web pages, not the address bar. Likewise, the NoSquint add-on applies only to web pages.

A short search on Mozilla's support website turn up the answer.

As with the zap to turn the address bar green, this also involves editing a Firefox file called userChrome.css. My first posting on this explained where this file is located in Windows, later I wrote about making this same modification in Linux and explained where the file is in Ubuntu and Mint.

To modify the address bar font size, add the following line to the userChrome.css file

#urlbar {font-size: 14pt !important}

If Firefox is running, you'll need to restart it to pick up the new font size. No doubt you'll want to experiment with a few different sizes.

The screen shot below shows this carried a bit far to illustrate the effect. 


It doesn't seem to matter where in the userChrome.css file you insert this new line. The item at the Mozilla forum says it should go after the "@namespace" line, but it works before it too.

I tested this using Firefox 3.5.2 and 3.013 on Windows XP and Firefox 3.06 running under Ubuntu 8.10.

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