How to make a flex child overflow its parent as it grows?

Question

I have a flexbox with a single flex child:

<div class="flex-parent">
  <div class="flex-child">
    lots of content...
  </div>
</div>

.flex-parent has a fixed size:

.flex-parent {
  height: 250px;
}

The flex child has so much content that it should overflow the size of its parent. Instead, its height stays "capped" at the height of the parent (250px).

How can I fix this and make .flex-child grow with its content? I can easily fix it by switching to display: block but my real layout is much more complicated which makes that impractical.

The problem: http://codepen.io/anon/pen/OWjYwe
How it should work: http://codepen.io/anon/pen/apyraV

`min-height:250px` - also, this has nothing to do with flexbox. — Adam Jenkins, Jan 25 '17 at 20:13
I am saying you **should** use `min-height` instead of `height`. Maybe I am misunderstanding, but it's not obvious what layout issue you might be trying to solve. — Adam Jenkins, Jan 25 '17 at 20:13
Thanks, but `.flex-parent` needs to stay the same size. I want `.flex-child` to grow. — BonsaiOak, Jan 25 '17 at 20:15
It's not obvious as to why anyone would need this behaviour. Perhaps you need to show a more complete example closer to what you need in practice. — Adam Jenkins, Jan 25 '17 at 20:16
Somehow, it makes no sense to let content grow taller a parent with a set height because it will hover lap any content that stands behind. What is the purpose of this ? hide something ? — G-Cyrillus, Jan 25 '17 at 20:24

score 3 · Accepted Answer · edited May 23 '17 at 12:24

The use of flex on a box with a single child might be useless unless for vertical/horizontal alignement.

To allow the flex-child to grow hover the setted height, then reset flex-direction to column:

see answer of @Michael B for details about flex item sizing algorithm

.flex-parent {
  display: flex;
  height: 200px;
  flex-flow: column;
  border: solid;
}
.flex-child {
  background: cornflowerblue;
}

<div class="flex-parent">
  <div class="flex-child">
    content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content
    content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content
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    content content content content content content content content content content content content content content content content content content content
  </div>
</div>
<p>What about me ?</p>

You may also use overflow but different behavior:

.flex-parent {
  display: flex;
  height: 200px;
  overflow:auto;
  border:solid;
}

.flex-child {
  background: cornflowerblue;
}

<div class="flex-parent">
  <div class="flex-child">
    content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content
    content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content
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    content content content content content content content content content content content content content content content content content content content
  </div>
</div>
<p>What about me ?</p>

Finally, use min-height instead height

.flex-parent {
  display: flex;
  min-height: 200px;
  border:solid;
}

.flex-child {
  background: cornflowerblue;
}

<div class="flex-parent">
  <div class="flex-child">
    content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content
    content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content
    content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content
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    content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content
    content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content
    content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content
    content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content
    content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content
    content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content content
    content content content content content content content content content content content content content content content content content content content
  </div>
</div>
<p>What about me ?</p>

score 2 · Answer 2 · edited May 23 '17 at 12:09

2

Switch the container to flex-direction: column.

This solution uses the flex item minimum sizing algorithm to achieve your layout.

A flex item, by default, cannot be smaller than the size of its content.

In row-direction, the initial setting on flex items is min-width: auto. But this doesn't help you because you're looking for vertical, not horizontal, expansion.

In column-direction, the initial setting is min-height: auto. This does help you. It ensures that the flex item is never shorter than the height of the content.

More details here: Why doesn't flex item shrink past content size?

edited May 23 '17 at 12:09

Community

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1

answered Jan 25 '17 at 20:16

Michael Benjamin

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Thanks for linking to the explanation of the algorithm. I wish I could accept both answers! – BonsaiOak Jan 25 '17 at 21:44

How to make a flex child overflow its parent as it grows?

2 Answers2