Q:

Bootstrap 4 "hidden" class doesn't work

I'm using Bootstrap v4 with it's default CSS and JS. I'm trying to apply the classes hidden, hidden-XX-down and hidden-XX-up to various divs, buttons, etc. But it doesn't seem to affect anything. All other classes work, except this one.
Here's an example:

<div class="row">

  <div class="col col-10 offset-1 hidden-sm-down">

    <p class="text-primary text-center">Lorem ipsum dolor sit amet.</p>

  </div>

</div>

I want the paragraph to be invisible when I resize the window to a smaller width (sm-down), yet it remains visible and nothing happens.

A:

Use d-none, d-sm-none, d-md-none etc.
https://getbootstrap.com/docs/4.0/utilities/display/
To only display for md up (hide for sm down) use: 
<div class="d-none d-md-block"></div>

