html - Flexbox: Header, centered body and sticky footer overflow

Question

Update This has been solved thanks to LGSon's comment below Updated codepen

I am trying to setup a layout much like the Holy grail. The difference here is that I am looking for a dynamically sized "Content" section to be vertically and horizontally centered.

I have been able to get this working (for large displays) with flexbox: Codepen here

html, body {
  width: 100%;
  height: 100%;
  margin: 0;
  padding: 0;
  text-align: center;
}

.header {
  height: 60px;
  line-height: 60px;
  width: 100%;
  background: rgba(255, 0, 0, 0.5);
}

.content {
  height: calc(100% - 120px);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background: rgba(0, 255, 0, 0.5);
}
.content p {
  width: 50%;
}

.footer {
  height: 60px;
  line-height: 60px;
  width: 100%;
  background: rgba(0, 0, 255, 0.5);
}

.header, .footer {
  font-weight: bold;
}

<div class="header">
    Header
</div>

<div class="content">
    <h1>I am the content</h1>
    <p>Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.</p>
</div>

<div class="footer">
    Footer
</div>

Answer 1

If you change your html, body rule to this

html, body {
  margin: 0;
  text-align: center;
  display: flex;
  flex-direction: column;
}

and then add this new rule

body {
  min-height: 100vh;
}

and then change from height: calc(100% - 120px); to flex-grow: 1; in your content rule it will work as you asked for.

The trick here is to make your body a flex container, and then, by setting the content to flex-grow: 1 it will fill the remaining space when the content is smaller, and the min-height: 100vh will allow it to properly grow higher than the viewport when the content is bigger.

Updated codepen

Stack snippet

html, body {
  margin: 0;
  text-align: center;
  display: flex;
  flex-direction: column;
}

body {
  min-height: 100vh;
}

.header {
  height: 60px;
  line-height: 60px;
  background: rgba(255, 0, 0, 0.5);
}

.content {
  flex-grow: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  background: rgba(0, 255, 0, 0.5);
}

.content p {
  width: 50%;
}

.footer {
  height: 60px;
  line-height: 60px;
  background: rgba(0, 0, 255, 0.5);
}

.header, .footer {
  font-weight: bold;
}

<div class="header">
    Header
</div>

<div class="content">
    <h1>I am the content</h1>
    <p>Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.
Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.Lorem Ipsum is simply dummy text of the printing and typesetting industry. Lorem Ipsum has been the industry's standard dummy text ever since the 1500s, when an unknown printer took a galley of type and scrambled it to make a type specimen book. It has survived not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.
</p>
</div>

<div class="footer">
    Footer
</div>