Font Awesome 5 - Choosing the correct font-family in CSS pseudo-elements

Question

I'm currently confused in using the icon in CSS pseudo-elements. There are 4 kind of font-family for fontawesome : Font Awesome 5 Free, Font Awesome 5 Solid, Font Awesome 5 Brands, Font Awesome 5 Regular

Here is the HTML :

<h1>Hello</h1>

Case 1

I use this icon : https://fontawesome.com/icons/twitter?style=brands

As you can see, its a brands icon, so font-family : Font Awesome 5 Brands

h1:before {
  display: inline-block;
  font-style: normal;
  font-variant: normal;
  text-rendering: auto;
  -webkit-font-smoothing: antialiased;
  content: "\f099"; /* TWITTER ICON */
  font-family: "Font Awesome 5 Brands";
  font-weight: 400;
}

IT WORKS!

Case 2

I use this icon : https://fontawesome.com/icons/phone?style=solid

As you can see, its a solid icon, so font-family : Font Awesome 5 Solid

h1:before {
  display: inline-block;
  font-style: normal;
  font-variant: normal;
  text-rendering: auto;
  -webkit-font-smoothing: antialiased;
  content: "\f095"; /* PHONE ICON */
  font-family: "Font Awesome 5 Solid";
  font-weight: 900;
}

DOESN'T WORK!

What did i do wrong?

How do we know when to use the correct font-family?

Answer 1

Simply use all of them in the same font-family and your browser will do the job. If it doesn't find it in the first one, it will use the second one. (Multiple fonts in Font-Family property?)

By the way, the correct font-family is Free not Solid because the difference between Solid and Regular is the font-weight and both have the same font-family. So there is no Solid and Regular in font-family, there is only Free and Brands.

You may also notice that almost all the Solid version of the icons are free BUT not all the regular version are free. Some of them are included in the PRO package. so if the icon is not showing it's not necessarely a font-family issue.

And all the Light version are PRO ones.

.icon {
  display: inline-block;
  font-style: normal;
  font-variant: normal;
  text-rendering: auto;
  -webkit-font-smoothing: antialiased;
  font-family: "Font Awesome 5 Brands","Font Awesome 5 Free";
}

.icon1:before {
  content: "\f099";
  /* TWITTER ICON */
  font-weight: 400;
}

.icon2:before {
  content: "\f095";
  /* PHONE ICON */
  font-weight: 900;
}

.icon3:before {
  content: "\f095";
  /* PHONE ICON */
  font-weight: 400;/*This one will not work because the regular version of the phone icon is in the Pro Package*/
}

<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.8.1/css/all.css" >

<div class="icon1 icon"></div>
<div class="icon2 icon"></div>
<br>

<div class="icon3 icon"></div>