Flexbox. Avoid child with longer height than parent (column direction)

Question

I'm scaffolding a basic UI for a site using flexbox. Quite similar to the usual email layout.

For some reason the second children( class .main-body, lightseagreen color) of a column-layouted flexbox container(.content-main, plum color) has a bigger height than its parent, which I do not want it to.

I made a codepen snippet to show this behaviour.

html,
body {
  width: 100%;
  height: 100%;
  background: lightblue;
  box-sizing: border-box;
}
* {
  box-sizing: border-box;
}
.container {
  height: inherit;
  background: PeachPuff;
  padding: 1em;
  display: flex;
  max-height: 500px;
}
.sidebar {
  flex: 0 1 15%;
  background: khaki;
}
.content {
  flex: 1 1 auto;
  background: plum;
  padding: 0.8em;
  display: flex;
  flex-direction: column;
}
.content-header {
  background: lightgreen;
  padding: 0.3em;
  flex: 0 0 7%;
}
.content-main {
  display: flex;
  background: darkseagreen;
  padding: 1em;
  height: 100%;
  flex: 1 1 auto;
}
.main-list {
  flex: 0 0 12%;
  background: lightcoral;
}
.main-body {
  flex: 0 1 auto;
  padding: 1em;
  background: lightcyan;
  display: flex;
  flex-flow: row wrap;
  overflow-y: scroll;
}

<div class='container'>
  <div class='sidebar'>
    <ul>
      <li>Onnnne</li>
      <li>Twoo</li>
      <li>Threee</li>
    </ul>
  </div>
  <div class='content'>
    <div class='content-header'>
      <span>This iscontent header</span>
    </div>
    <div class='content-main'>
      <div class='main-list'>
        <ul>
          <li>List 1</li>
          <li>List 2</li>
          <li>List 3</li>
        </ul>
      </div>
      <div class='main-body'>
        <div class='panel'>
          <table>
            <thead>
              <th>First</th>
              <th>Second</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
            </thead>
            <tbody>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
            </tbody>
          </table>
        </div>
        <div class='panel'>
          <table>
            <thead>
              <th>First</th>
              <th>Second</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
            </thead>
            <tbody>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
            </tbody>
          </table>
        </div>
        <div class='panel'>
          <table>
            <thead>
              <th>First</th>
              <th>Second</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
            </thead>
            <tbody>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
            </tbody>
          </table>
        </div>
        <div class='panel'>
          <table>
            <thead>
              <th>First</th>
              <th>Second</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
            </thead>
            <tbody>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
            </tbody>
          </table>
        </div>
        <div class='panel'>
          <table>
            <thead>
              <th>First</th>
              <th>Second</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
            </thead>
            <tbody>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
            </tbody>
          </table>
        </div>
        <div class='panel'>
          <table>
            <thead>
              <th>First</th>
              <th>Second</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
            </thead>
            <tbody>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
    </div>
  </div>
</div>

How can I prevent the green child to have bigger height than its plum parent? I want the child to just be scrollable but never taller than its parents.

score 73 · Answer 1 · answered Dec 07 '15 at 23:41

Flexbox introduces auto as the new initial value of min-height. It makes flex items grow as tall as their contents.

You can undo that by setting min-height to 0, the old initial value:

.content-main {
  min-height: 0;
}

html,
body {
  width: 100%;
  height: 100%;
  background: lightblue;
  box-sizing: border-box;
}
* {
  box-sizing: border-box;
}
.container {
  height: inherit;
  background: PeachPuff;
  padding: 1em;
  display: flex;
  max-height: 500px;
}
.sidebar {
  flex: 0 1 15%;
  background: khaki;
}
.content {
  flex: 1 1 auto;
  background: plum;
  padding: 0.8em;
  display: flex;
  flex-direction: column;
}
.content-header {
  background: lightgreen;
  padding: 0.3em;
  flex: 0 0 7%;
}
.content-main {
  display: flex;
  background: darkseagreen;
  padding: 1em;
  height: 100%;
  flex: 1 1 auto;
  min-height: 0;
}
.main-list {
  flex: 0 0 12%;
  background: lightcoral;
}
.main-body {
  flex: 0 1 auto;
  padding: 1em;
  background: lightcyan;
  display: flex;
  flex-flow: row wrap;
  overflow-y: scroll;
}

<div class='container'>
  <div class='sidebar'>
    <ul>
      <li>Onnnne</li>
      <li>Twoo</li>
      <li>Threee</li>
    </ul>
  </div>
  <div class='content'>
    <div class='content-header'>
      <span>This iscontent header</span>
    </div>
    <div class='content-main'>
      <div class='main-list'>
        <ul>
          <li>List 1</li>
          <li>List 2</li>
          <li>List 3</li>
        </ul>
      </div>
      <div class='main-body'>
        <div class='panel'>
          <table>
            <thead>
              <th>First</th>
              <th>Second</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
            </thead>
            <tbody>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
            </tbody>
          </table>
        </div>
        <div class='panel'>
          <table>
            <thead>
              <th>First</th>
              <th>Second</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
            </thead>
            <tbody>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
            </tbody>
          </table>
        </div>
        <div class='panel'>
          <table>
            <thead>
              <th>First</th>
              <th>Second</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
            </thead>
            <tbody>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
            </tbody>
          </table>
        </div>
        <div class='panel'>
          <table>
            <thead>
              <th>First</th>
              <th>Second</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
            </thead>
            <tbody>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
            </tbody>
          </table>
        </div>
        <div class='panel'>
          <table>
            <thead>
              <th>First</th>
              <th>Second</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
            </thead>
            <tbody>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
            </tbody>
          </table>
        </div>
        <div class='panel'>
          <table>
            <thead>
              <th>First</th>
              <th>Second</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
              <th>Third</th>
            </thead>
            <tbody>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
              <tr>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
                <td>1</td>
              </tr>
            </tbody>
          </table>
        </div>
      </div>
    </div>
  </div>
</div>

Fantastic, thanks @Oriol for the editing and answer. One related question I'm struggling to answer is: why does `min-height: auto` make it grow (column-oriented) until it reaches its grandparent `.container`'s height instead of make it grow until its direct parent `.content`'s height? Cause that's what it's doing right, since we're using `border-box` box model? — lllllll, Dec 08 '15 at 00:07
@vint-i-vuit Yeah, in fact I oversimplified it in the answer, see [the spec](http://www.w3.org/TR/css-flexbox-1/#min-size-auto) for full details. In this case, since `.content-main` has a specified size (`height: 100%`), the minimum height will be the smallest between that `100%` and the content size. This produces the effect you describe. — Oriol, Dec 08 '15 at 00:19
Thanks, I got it working! Full example: https://jsfiddle.net/gatorade20/rnLepgto/1/ — serg06, Aug 07 '21 at 15:56

Flexbox. Avoid child with longer height than parent (column direction)

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