Example

<h1>Heading level 1</h1>
<h2>Heading level 2</h2>
<h3>Heading level 3</h3>
<h4>Heading level 4</h4>
<h5>Heading level 5</h5>
<h6>Heading level 6</h6>

Result:

Example

h1, h2, h3, h4, h5, h6,
.h1, .h2, .h3, .h4, .h5, .h6 {
  margin-bottom: 0.5rem;
  font-weight: 500;
  line-height: 1.2;
}

h1, .h1 {
  font-size: 2.5rem;
}

h2, .h2 {
  font-size: 2rem;
}

h3, .h3 {
  font-size: 1.75rem;
}

h4, .h4 {
  font-size: 1.5rem;
}

h5, .h5 {
  font-size: 1.25rem;
}

h6, .h6 {
  font-size: 1rem;
}