wagtail/client/scss/tools/_mixins.fonts.scss

/*
NB: Due to Wagtail's browser support the following @font-face formats are required:
- WOFF for modern browsers
- WOFF2 For super-modern browsers

This example is all we need now:

@font-face {
  font-family: 'MyWebFont';
  src: url('myfont.woff2') format('woff2'),
       url('myfont.woff') format('woff');
}

See https://css-tricks.com/snippets/css/using-font-face/ for more information.

*/

@mixin webfont($fontname, $filestub, $weight, $style:normal) {
    @font-face {
        font-family: '#{$fontname}';
        src: url('#{$font-root}#{$filestub}.woff2') format('woff2'),
            url('#{$font-root}#{$filestub}.woff') format('woff');
        font-weight: $weight;
        font-style: $style;
    }
}