Bootstrap 3 equal height thumbnails (like equal height cards in bootstrap 4)

Question

I have a row of thumbnails like this:

I want them to be equal height though. This is my code:

<div class="row text-center">
    <div class="col-md-3 col-sm-6">
        <div class="thumbnail">
            <div class="caption">
                <h3>HOTKEY + COMBO</h3>
                <p>Hotkey description goes here. Category only shown in explore.</p>
                <p>
                    <a href="#" class="btn btn-default" data-tooltip="Change Hotkey">
                </p>
            </div>
        </div>
    </div>
    <div class="col-md-3 col-sm-6">
        <div class="thumbnail">
            <div class="caption">
                <h3>HOTKEY + COMBO</h3>
                <p>short desc</p>
                <p>
                    <a href="#" class="btn btn-default" data-tooltip="Change Hotkey">
                </p>
            </div>
        </div>
    </div>
    <div class="col-md-3 col-sm-6 hotkey-add">
        <div class="thumbnail">
            <div class="caption">
                <p></p>
                <p><a href="#" class="btn btn-default"><span class="glyphicon glyphicon-plus"></span></a></p>
            </div>
        </div>
    </div>
</div>

Is this possible? Like we see in bootstrap4 here is equal height cards:

http://www.codeply.com/render/KrUO8QpyXP#

Answer 1

I know I'm a little late on this, but I think the best way is flexbox. Here's how it would work in Bootstrap 3:

.row.display-flex {
  display: flex;
  flex-wrap: wrap;
}
.thumbnail {
  height: 100%;
}

Just add display-flex to the containing row. Also, the upcoming Bootstrap 4 has flexbox as the default so this extra CSS won't be necessary in the future.

Thumbnails with flexbox

You can also do more with the position of child elements.

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Also see, make Bootstrap columns all the same height

Answer 2

It seems that bootstrap 4, like you show in the example, is using to get the same height, display: table for the container div and display: table-cell for the inner ones.

Other solution can be using <table> instead <div>, using flex property...
Checkout this How can I make Bootstrap columns all the same height?