They use Fira Sans and Fira Mono in a bunch of different weights. Looking at the source for <http://www.gnu.org/software/emacs/fira.css> http://www.gnu.org/sof

They use Fira Sans and Fira Mono in a bunch of different weights. Looking at the source for <http://www.gnu.org/software/emacs/fira.css> http://www.gnu.org/software/emacs/fira.css>, I can't help but wonder if mobile^W OS vendors could make the Web faster for their users if they'd just bundle every single popular free (beer and/or speech) font with their OSs and keep the fonts up-to-date. Of course, you should be sending along far-future Expires and Cache-Control headers, but this'll still be slower than local() accessing fonts that're bundled with the OS when someone visits a new site.