small modal popup bootstrap

1<!-- Button trigger modal -->
2<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModalCenter">
3  Launch demo modal
4</button>
5
6<!-- Modal -->
7<div class="modal fade" id="exampleModalCenter" tabindex="-1" role="dialog" aria-labelledby="exampleModalCenterTitle" aria-hidden="true">
8  <div class="modal-dialog modal-dialog-centered" role="document">
9    <div class="modal-content">
10      <div class="modal-header">
11        <h5 class="modal-title" id="exampleModalLongTitle">Modal title</h5>
12        <button type="button" class="close" data-dismiss="modal" aria-label="Close">
13          <span aria-hidden="true">×</span>
14        </button>
15      </div>
16      <div class="modal-body">
17        ...
18      </div>
19      <div class="modal-footer">
20        <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
21        <button type="button" class="btn btn-primary">Save changes</button>
22      </div>
23    </div>
24  </div>
25</div>