Left & right align modal footer buttons in Bootstrap 4

Question

Bootstrap 4 uses flex-box for it's modal footers. If I want two buttons, one on the left and one on the right, how do I get it to work properly?

The code below tries to use a div.row with col-sm-6 but doesn't work.

<script src="https://code.jquery.com/jquery-3.1.1.slim.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.4.0/js/tether.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/js/bootstrap.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" rel="stylesheet"/>

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

<!-- Modal -->
<div class="modal fade" id="myModal" 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">&times;</span>
        </button>
      </div>
      <div class="modal-body">
        ...
      </div>
      <div class="modal-footer">
      <div class="row">
        <div class="col-sm-6 text-left">
        <button type="button" class="btn btn-primary">Save changes</button>
        </div>
        <div class="col-sm-6 text-right">
        <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
        </div>
      </div>
      </div>
    </div>
  </div>
</div>

Answer 1

Now that the modal-footer is "display:flex" in Bootstrap 4, it would be easiest to use the auto-margins. Use mr-auto on the left button.

<div class="modal-footer">
     <button type="button" class="btn btn-primary mr-auto">Save changes</button>
     <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
</div>

Demo

Also see: Left align and right align within div in Bootstrap

---

Follow-up to comment "What if I need the button on the right to occupy all the space left?" - Use the btn-block class:

<div class="modal-footer">
     <button type="button" class="btn btn-primary text-nowrap">Save changes</button>
     <button type="button" class="btn btn-secondary btn-block ml-1" data-dismiss="modal">Close</button>
</div>

Answer 2

The modal-footer is display:flex;. So the better way to align its elements (e.g. buttons) is by using flex rules. Bootstrap 4 provides new utilities classes to modify those flex rules (e.g. .justify-content-[modifier]). So I think a better option should be as follows:

<div class="modal-footer justify-content-between">
  <button type="button" class="btn btn-primary">Save changes</button>
  <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
</div>

<script src="https://code.jquery.com/jquery-3.1.1.slim.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/tether/1.4.0/js/tether.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/js/bootstrap.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" rel="stylesheet"/>

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

<!-- Modal -->
<div class="modal fade" id="myModal" 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">&times;</span>
        </button>
      </div>
      <div class="modal-body">
        ...
      </div>
      <div class="modal-footer justify-content-between">
        <button type="button" class="btn btn-primary">Save changes</button>
        <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
      </div>
    </div>
  </div>
</div>

Answer 3

The only way it works in IE is using w-100. mx-auto and mr and ml-auto all seems to overflow the buttons from the containing element.

<div class="modal-footer">
  <div class="w-100">
    <button type="button" class="btn btn-default">Cancel</button>
    <button type="button" class="btn btn-primary float-right">Save</button>
  </div>
</div>

Answer 4

For anyone that wants 3 buttons, for example 2 on the right and 1 on the left:

<div class="modal-footer justify-content-between">                    
   <button type="submit" class="btn btn-danger">Delete</button>                                    
   <div>
       <button type="button" class="btn btn-secondary" data-dismiss="modal">Close</button>
       <button type="submit" class="btn btn-primary">Save changes</button>
   </div>  
</div>