<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css"> <script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script> <script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script> <!------ Include the above in your HEAD tag ----------> <div class="container center"> <div class="row"> <h2 class="block-center">Bootstrap modal center</h2> </div> <div class="row"> <button type="button" class="btn btn-primary" data-toggle="modal" data-target="#exampleModal">Modal center</button> </div> </div> <!-- Modal --> <div class="modal fade" id="exampleModal" tabindex="-1" role="dialog" aria-labelledby="exampleModalLabel" aria-hidden="true"> <div class="modal-dialog" role="document"> <div class="modal-content"> <div class="modal-header"> <h5 class="modal-title" id="exampleModalLabel">Modal title</h5> <button type="button" class="close" data-dismiss="modal" aria-label="Close"> <span aria-hidden="true">×</span> </button> </div> <div class="modal-body"> ... </div> <div class="modal-footer"> <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button> <button type="button" class="btn btn-primary">Save changes</button> </div> </div> </div> </div>

.modal { text-align: center; } @media screen and (min-width: 768px) { .modal:before { display: inline-block; vertical-align: middle; content: " "; height: 100%; } } .modal-dialog { display: inline-block; text-align: left; vertical-align: middle; }