bootstrap 4 button group responsive - html

Question

Good day,
I have a little issue with bootstrap button groups. Probably I am doing something wrong or I am overlooking something. But I am running a bit at a dead end here. So I hope that someone could shed a bit of light on this topic.
I have a couple of buttons set inside of a bootstrap group.
The buttons are nicely aligned and appear as they should.
Except for mobile.
When I resize the window however I notice that the buttons stay horizontally aligned. They do not automatically form a row such as bootstrap columns.
Now this is exactly what I would like. Since I want those buttons to form a toolbar that is usable on a mobile phone as well.
<div class="container">
<div class="row">
<div class="col-md-12">
<div class="btn-group mr-2" role="group" aria-label="button group">
<button type="button" class="btn btn-default">button one</button>
<button type="button" class="btn btn-default">button two</button>
<button type="button" class="btn btn-default">button three</button>
<button type="button" class="btn btn-default">button four</button>
<button type="button" class="btn btn-default">button five</button>
<button type="button" class="btn btn-default">button six</button>
</div>
</div>
</div>
</div>
Take the code above.
That generates the following :
But when resizing the thing I get :
Whilst I would like the buttons to resize or order in a way they are suitable as a toolbar functioning for mobile phones.

Answer 1

You need to actually size the buttons inside your container grid.
https://getbootstrap.com/docs/4.3/layout/grid/
<div class="container">
<div class="col-md-12">
<div class="btn-group row" role="group" aria-label="button group">
<button type="button" class="btn btn-default col-md-2">button one</button>
<button type="button" class="btn btn-default col-md-2">button two</button>
<button type="button" class="btn btn-default col-md-2">button three</button>
<button type="button" class="btn btn-default col-md-2">button four</button>
<button type="button" class="btn btn-default col-md-2">button five</button>
<button type="button" class="btn btn-default col-md-2">button six</button>
</div>
</div>
</div>

Answer 2

What you see is the default behavior of the button-group class... so we can define our own rule for the width breakpoint where the scroll starts to emerge by adding the following CSS:
#media screen and (max-width:576px){
.btn-group{display:flex; flex-direction: column;}
}
Complete snippet below:
#media screen and (max-width:576px) {
.btn-group {
display: flex;
flex-direction: column;
}
}
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.3.1/css/bootstrap.min.css">
<div class="container">
<div class="row">
<div class="col-md-12">
<div class="btn-group mr-2 " role="group" aria-label="button group">
<button type="button" class="btn btn-default">button one</button>
<button type="button" class="btn btn-default">button two</button>
<button type="button" class="btn btn-default">button three</button>
<button type="button" class="btn btn-default">button four</button>
<button type="button" class="btn btn-default">button five</button>
<button type="button" class="btn btn-default">button six</button>
</div>
</div>
</div>
</div>