Overleaf/services/web/frontend/stylesheets/bootstrap-5/base/typography.scss

// Headings

// Headings
h1,
h2,
h3,
h4,
h5,
h6,
.h1,
.h2,
.h3,
.h4,
.h5,
.h6 {
  // Apply margin above the heading only when it has a preceding sibling or is inside a row with a preceding sibling
  * > * + &,
  * + .row & {
    margin-top: $spacing-08;
  }
}

h1,
.h1 {
  @include heading-xl;
}

h2,
.h2 {
  @include heading-md;
}

h3,
.h3 {
  @include heading-sm;
}

h4,
.h4 {
  @include heading-xs;
}

h5,
.h5 {
  @include body-base;
}

h6,
.h6 {
  @include body-sm;
}

// Miscellaneous
.small {
  @include body-sm;
}