<!-- Button trigger modal -->
<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#basicModal">
    Launch demo modal
</button>

<!-- Modal -->
<div class="modal fade" id="basicModal" role="dialog" aria-hidden="true">
    <div class="modal-dialog" role="document">
        <div class="modal-content">
            <div class="modal-header">
                <h5 class="modal-title">Modal title</h5>
                <button type="button" class="close" data-dismiss="modal">
                    <span aria-hidden="true">&times;</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>

Scrolling Long Content Modal

<!-- Button trigger modal -->
<button type="button" class="btn btn-dark" data-toggle="modal" data-target="#basicModalLong">
    Launch demo modal
</button>

<!-- Modal -->
<div class="modal fade" id="basicModalLong" role="dialog" aria-hidden="true">
    <div class="modal-dialog modal-dialog-scrollable" role="document">
        <div class="modal-content">
            <div class="modal-header">
                <h5 class="modal-title">Modal title</h5>
                <button type="button" class="close" data-dismiss="modal">
                    <span aria-hidden="true">&times;</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>
<!-- Button trigger modal -->
<button type="button" class="btn btn-outline-info" data-toggle="modal" data-target="#basicModalCenter">
    Launch demo modal
</button>

<!-- Modal -->
<div class="modal fade" id="basicModalCenter" role="dialog" aria-hidden="true">
    <div class="modal-dialog modal-dialog-centered" role="document">
        <div class="modal-content">
            <div class="modal-header">
                <h5 class="modal-title">Modal title</h5>
                <button type="button" class="close" data-dismiss="modal">
                    <span aria-hidden="true">&times;</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>
<!-- Button trigger modal -->
<button type="button" class="btn btn-primary" data-toggle="modal" data-target="#basicStaticBackdrop">
    Launch demo modal
</button>

<!-- Modal -->
<div class="modal fade" id="basicStaticBackdrop" data-backdrop="static" role="dialog" aria-hidden="true">
    <div class="modal-dialog" role="document">
        <div class="modal-content">
            <div class="modal-header">
                <h5 class="modal-title">Modal title</h5>
                <button type="button" class="close" data-dismiss="modal">
                    <span aria-hidden="true">&times;</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>
<!-- Button trigger modal -->
<button type="button" class="btn btn-primary" data-toggle="modal" data-target=".basicModalXL">
    Extra large modal
</button>

<!-- Modal -->
<div class="modal fade basicModalXL" role="dialog" aria-hidden="true">
    <div class="modal-dialog modal-xl" role="document">
        <div class="modal-content">
            <div class="modal-header">
                <h5 class="modal-title">Extra large modal</h5>
                <button type="button" class="close" data-dismiss="modal">
                    <span aria-hidden="true">&times;</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>
<!-- Button trigger modal -->
<button type="button" class="btn btn-primary" data-toggle="modal" data-target=".basicModalLG">
    Large modal
</button>

<!-- Modal -->
<div class="modal fade basicModalLG" role="dialog" aria-hidden="true">
    <div class="modal-dialog modal-lg" role="document">
        <div class="modal-content">
            <div class="modal-header">
                <h5 class="modal-title">Large modal</h5>
                <button type="button" class="close" data-dismiss="modal">
                    <span aria-hidden="true">&times;</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>
<!-- Button trigger modal -->
<button type="button" class="btn btn-primary" data-toggle="modal" data-target=".basicModalSM">
    Small modal
</button>

<!-- Modal -->
<div class="modal fade basicModalSM" role="dialog" aria-hidden="true">
    <div class="modal-dialog modal-sm" role="document">
        <div class="modal-content">
            <div class="modal-header">
                <h5 class="modal-title">Small modal</h5>
                <button type="button" class="close" data-dismiss="modal">
                    <span aria-hidden="true">&times;</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>