system-fonts.css

body {
  font-family: -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Oxygen-Sans,Ubuntu,Cantarell,"Helvetica Neue",sans-serif;
}

/* Define the "system" font family */
@font-face {
  font-family: system;
  font-style: normal;
  font-weight: 300;
  src: local(".SFNSText-Light"), local(".HelveticaNeueDeskInterface-Light"), local(".LucidaGrandeUI"), local("Ubuntu Light"), local("Segoe UI Light"), local("Roboto-Light"), local("DroidSans"), local("Tahoma");
}

/* Now, let's apply it on an element */
body {
  font-family: "system";
}