Font-Awesome/js-packages/@fortawesome/fontawesome-free/less/_core.less

// base icon class definition
// -------------------------

.@{fa-css-prefix} {
  font-family: ~"var(--@{fa-css-prefix}-style-family, '@{fa-style-family}')";
  font-weight: ~'var(--@{fa-css-prefix}-style, @{fa-style})';
}

.fas,
.far,
.fab,
.@{fa-css-prefix}-solid,
.@{fa-css-prefix}-regular,
.@{fa-css-prefix}-brands,

.@{fa-css-prefix}-sharp-solid,
.@{fa-css-prefix}-classic,
.@{fa-css-prefix} {
  -moz-osx-font-smoothing: grayscale;
  -webkit-font-smoothing: antialiased;
  display: ~'var(--@{fa-css-prefix}-display, @{fa-display})';
  font-style: normal;
  font-variant: normal;
  line-height: 1;
  text-rendering: auto;
}

.fas::before,
.far::before,
.fab::before,
.@{fa-css-prefix}-solid::before,
.@{fa-css-prefix}-regular::before,
.@{fa-css-prefix}-brands::before,
.fa::before {
  content: ~'var(@{fa-icon-property})';
}

.@{fa-css-prefix}-classic,
.fas,
.@{fa-css-prefix}-solid,
.far,
.@{fa-css-prefix}-regular {
  font-family: 'Font Awesome 6 Free';
}
.@{fa-css-prefix}-brands,
.fab {
  font-family: 'Font Awesome 6 Brands';
}