Which of these fonts will the browser use?

Question

css

Which of these fonts is used by default. This is part of the style from fontawesome. There are many fonts, and what is used is unknown.

Why do I need it? I want to add them to preload.

@font-face {
  font-family: 'Font Awesome 5 Free';
  font-style: normal;
  font-weight: 400;
  font-display: block;
  src: url("../webfonts/fa-regular-400.eot");
  src: url("../webfonts/fa-regular-400.eot?#iefix") format("embedded-opentype"), url("../webfonts/fa-regular-400.woff2") format("woff2"), url("../webfonts/fa-regular-400.woff") format("woff"), url("../webfonts/fa-regular-400.ttf") format("truetype"), url("../webfonts/fa-regular-400.svg#fontawesome") format("svg"); 
}

Answer 1

1 - you can look in chrome dev tools in the network tab - there will be .woff2
2 - each browser will choose the font that it supports
3 - browsers that understand rel preload https://caniuse.com/#feat=link-rel- preload will use .woff2