bootstrap 4 card custom css code example

Example 1: responsive card header

<div class="card" style="width: 18rem;">
  <div class="card-header">
    Featured
  </div>
  <ul class="list-group list-group-flush">
    <li class="list-group-item">Cras justo odio</li>
    <li class="list-group-item">Dapibus ac facilisis in</li>
    <li class="list-group-item">Vestibulum at eros</li>
  </ul>
</div>

Example 2: how to add listed card to a div bootstrap

<div class="card-columns">
  <div class="card">
    <img class="card-img-top" src="..." alt="Card image cap">
    <div class="card-body">
      <h5 class="card-title">Card title that wraps to a new line</h5>
      <p class="card-text">This is a longer card with supporting text below as a natural lead-in to additional content. This content is a little bit longer.</p>
    </div>
  </div>
  <div class="card p-3">
    <blockquote class="blockquote mb-0 card-body">
      <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer posuere erat a ante.</p>
      <footer class="blockquote-footer">
        <small class="text-muted">
          Someone famous in <cite title="Source Title">Source Title</cite>
        </small>
      </footer>
    </blockquote>
  </div>
  <div class="card">
    <img class="card-img-top" src="..." alt="Card image cap">
    <div class="card-body">
      <h5 class="card-title">Card title</h5>
      <p class="card-text">This card has supporting text below as a natural lead-in to additional content.</p>
      <p class="card-text"><small class="text-muted">Last updated 3 mins ago</small></p>
    </div>
  </div>
  <div class="card bg-primary text-white text-center p-3">
    <blockquote class="blockquote mb-0">
      <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer posuere erat.</p>
      <footer class="blockquote-footer">
        <small>
          Someone famous in <cite title="Source Title">Source Title</cite>
        </small>
      </footer>
    </blockquote>
  </div>
  <div class="card text-center">
    <div class="card-body">
      <h5 class="card-title">Card title</h5>
      <p class="card-text">This card has supporting text below as a natural lead-in to additional content.</p>
      <p class="card-text"><small class="text-muted">Last updated 3 mins ago</small></p>
    </div>
  </div>
  <div class="card">
    <img class="card-img" src="..." alt="Card image">
  </div>
  <div class="card p-3 text-right">
    <blockquote class="blockquote mb-0">
      <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Integer posuere erat a ante.</p>
      <footer class="blockquote-footer">
        <small class="text-muted">
          Someone famous in <cite title="Source Title">Source Title</cite>
        </small>
      </footer>
    </blockquote>
  </div>
  <div class="card">
    <div class="card-body">
      <h5 class="card-title">Card title</h5>
      <p class="card-text">This is a wider card with supporting text below as a natural lead-in to additional content. This card has even longer content than the first to show that equal height action.</p>
      <p class="card-text"><small class="text-muted">Last updated 3 mins ago</small></p>
    </div>
  </div>
</div>