Modifying Firefox and Thunderbird menu fonts

I use Mozilla Firefox for browsing and Mozilla Thunderbird for e-mail… two awesome free software apps you can run on GNU/Linux, MacOS, or Windows.

One niggling annoyance I found with these, however, is that changing your fonts in KDE or Gnome changes the fonts for every other application on your system except for these two holdouts. That’s because they use something separate to generate their menus, called XML User Interface Language (XUL). The good news is this is easy to remedy by creating and modifying a file called userChrome.css .  If you understand CSS you can also tweak it to your heart’s content.  Most of the time, Firefox keeps your data in


and Thunderbird in


In those folders should be a folder named chrome, where userChrome.css needs to go.  The Firefox chrome folder also contains an example file called (of all things) userChrome-example.css if you’d like something more detailed.  But if you just want a quick way to change all the fonts at once, here is an example userChrome.css .  Notice that a font with spaces in it needs “quotes” around it:

* Do not remove the @namespace line -- it's required for correct functioning
@namespace url(""); /* set default namespace to XUL */

/* Added manually to fix Mozilla fonts */
* {
font-size: 10pt !important;
font-family: "Liberation Serif", Serif !important;

You can change the font-size up or down, higher numbers for larger fonts.  Between the quotes after font-family , you can put the name of any font installed on your system… Liberation Serif, Arial, Verdana, Times New Roman, etc.  Here I’ve set it to use Liberation Serif, and fall back to Serif if Liberation Serif becomes unavailable for some reason (such as if I transfer my data to another computer).

You can do this once each for Thunderbird and Firefox… problem solved!



Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s