How can I make Flexbox children 100% height of their parent?

I'm trying to fill the vertical space of a flex item inside a Flexbox.

.container {
  height: 200px;
  width: 500px;
  display: flex;
  flex-direction: row;
}
.flex-1 {
  width: 100px;
  background-color: blue;
}
.flex-2 {
  position: relative;
  flex: 1;
  background-color: red;
}
.flex-2-child {
  height: 100%;
  width: 100%;
  background-color: green;
}

<div class="container">
  <div class="flex-1"></div>
  <div class="flex-2">
    <div class="flex-2-child"></div>
  </div>
</div>

And here's the JSFiddle

flex-2-child doesn't fill the required height except in the two cases where:

1. flex-2 has a height of 100% (which is weird because a flex item has a 100% by default + it is buggy in Chrome)
2. flex-2-child has a position absolute which is also inconvenient

This doesn't work in Chrome or Firefox currently.

Solution 1:

Use align-items: stretch

Similar to David Storey's answer, my workaround is:

.flex-2 {
    display: flex;
    align-items: stretch;
}

Note that height: 100% should be removed from the child component (see comments).

Alternatively to align-items, you can use align-self just on the .flex-2-child item you want stretched.

Solution 2:

I have answered a similar question here.

I know you have already said position: absolute; is inconvenient, but it works. See below for further information on fixing the resize issue.

Also see this jsFiddle for a demo, although I have only added WebKit prefixes so open in Chrome.

You basically have two issues which I will deal with separately.

1. Getting the child of a flex-item to fill height 100%

• Set position: relative; on the parent of the child.
• Set position: absolute; on the child.
• You can then set width/height as required (100% in my sample).

2. Fixing the resize scrolling "quirk" in Chrome

• Put overflow-y: auto; on the scrollable div.
• The scrollable div must have an explicit height specified. My sample already has height 100%, but if none is already applied you can specify height: 0;

See this answer for more information on the scrolling issue.

Solution 3:

If I understand correctly, you want flex-2-child to fill the height and width of its parent, so that the red area is fully covered by the green?

If so, you just need to set flex-2 to use Flexbox:

.flex-2 {
    display: flex;
}

Then tell flex-2-child to become flexible:

.flex-2-child {
    flex: 1;
}

See http://jsfiddle.net/2ZDuE/10/

The reason is that flex-2-child is not a Flexbox item, but its parent is.