CSS transition auto width

css animation css-transitions css-animations
Luke Taylor picture Luke Taylor · Jul 28, 2016 · Viewed 29.4k times · Source

I have an element whose width I'd like to animate when its contents change. It has width: auto, and this never changes. I've seen this trick, but that's for transitioning between two values and one is set. I'm not manipulating the values at all, only the content, and I'd like my element's size to change with animation. Is this at all possible in CSS?

Here's a simplified version of my code:

I'd like the changing size to animate when the user hovers over the element.

Answer

Ason picture Ason · Jul 28, 2016

As I commented, one can't animate auto (yet), so either use the max-width/max-height trick, or, if you need it to be more exact, set the width using a script.

With the max-width/max-height trick, give it a value big enough to accommodate the widest.

Stack snippet

.myspan {
  display: inline-block;
  font-size: 30px;
  background-color: #ddd;
  vertical-align: bottom;
}
.myspan::after {
  content: " \00a0\f12a ";
  font-family: ionicons;
  font-size: 80%;  
  display: inline-block;
  max-width: 0;
  transition: max-width .6s;
  vertical-align: bottom;
  overflow: hidden;
}
.myspan:hover::after {
  max-width: 80px;
  transition: max-width 1s;
}
<link href="https://code.ionicframework.com/ionicons/2.0.1/css/ionicons.min.css" rel="stylesheet" />

<span class="myspan">Hello!</span>

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