Targetting the OS X System Font in CSS

body {
  font-family: system-font, -webkit-system-font, -apple-system-font, ".SFNSDisplay-Regular", HelveticaNeue, LucidaGrande;
}

On a fresh install of OS X 10.11 (El Capitan) there’s no San Francisco font installed. But it’s the system font, so how is this possible?

Hence the sort of magic above to actually get it working.

I Left My System Fonts in San Francisco →