Bootstrap/scss/utilities/_display.scss

//
// Display utilities
//


@each $breakpoint in map-keys($grid-breakpoints) {
  @include media-breakpoint-up($breakpoint) {
    $min: breakpoint-min($breakpoint, $grid-breakpoints);

    @if $min {
      .d-#{$breakpoint}-none { display: none !important; }
      .d-#{$breakpoint}-inline { display: inline !important; }
      .d-#{$breakpoint}-inline-block { display: inline-block !important; }
      .d-#{$breakpoint}-block { display: block !important; }
      .d-#{$breakpoint}-table { display: table !important; }
      .d-#{$breakpoint}-table-cell { display: table-cell !important; }
      .d-#{$breakpoint}-flex { display: flex !important; }
    } @else {
      .d-none { display: none !important; }
      .d-inline { display: inline !important; }
      .d-inline-block { display: inline-block !important; }
      .d-block { display: block !important; }
      .d-table { display: table !important; }
      .d-table-cell { display: table-cell !important; }
      .d-flex { display: flex !important; }
    }
  }
}