I specify the icon I want to apply on my button with bootstrap, but it only appears empty on the page... What’s going on?

Question

<div>
    <span>TROCO</span>
    <button type="button" class="btn btn-outline-dark" data-toggle="collapse" data-target="#collapse" aria-expanded="true" aria-controls="collapseExample">
        <span class="glyphicon glyphicon-ok" aria-hidden="true"></span>
    </button>

    <div class="collapse" id="collapse">
        <div class="card card-body">
            texto
        </div>
    </div>
</div>

This is the snippet that has the button. The icon simply does not appear...

Answer 1

Which version of bootstrap are you using? version 4 no longer has glyphicon. instead use https://fontawesome.com/v4.7.0 fontawesome this in version 6 plus the 4.7 is very good. if you go to 3 you can do so