In the spirit of fitting as much as I can onn my screen when using Gwibber, I needed to change its fonts. I was surprised to only see an option to change themes.

There is a bug open about having font preferences in Gwibber (#460069) but it seems the fix was dropped. While I get an answer about this, I also came about this slightly related post on OMG! Ubuntu!.

From a terminal window, I edited the stylesheet file for the Ubuntu theme in Gwibber:

gksudo gedit /usr/share/gwibber/ui/themes/ubuntu/main.css

The beginning of my file looks like this now:

* {
  color: black;
  font-size: 8pt;
  font-family: Liberation Sans;
}

.imgbox {
  -webkit-border-radius: 5px;
}

.tableBubble {
	width:100%;
}

You will need to exit Gwibber and restart it to see the changes.

To see what fonts you have available and their corresponding family names, install the gnome-specimen package and then go to Applications > Graphics > Specimen Font Previewer.