align-content

Distributes the space between the lines of a flex container on the cross axis. It only has an effect when there are multiple lines, that is, with flex-wrap: wrap.

stretch (default): lines stretch to take up the available space.
flex-start: packs the lines at the start.
center: packs the lines in the center.
flex-end: packs the lines at the end.
space-between: the first and last lines touch the edges and the rest are spread between them.
space-around: leaves the same space around each line.
space-evenly: leaves identical spaces between lines and at the edges.

Example

This container has a fixed height and several lines. Change align-content to distribute the rows. If you remove flex-wrap in the editor, you will see it no longer has any effect.

ResultLiveContainer width30%

html

<div class="container">
  <div class="child">1</div>
  <div class="child">2</div>
  <div class="child">3</div>
  <div class="child">4</div>
  <div class="child">5</div>
  <div class="child">6</div>
</div>

<div class="container">
  <div class="child">1</div>
  <div class="child">2</div>
  <div class="child">3</div>
  <div class="child">4</div>
  <div class="child">5</div>
  <div class="child">6</div>
</div>

css

.container {
  border: 1px solid #2b7de0;
  display: flex;
  gap: 1rem;
  align-content: stretch;
  flex-wrap: wrap;
  height: 16rem;
  padding: 0.5rem;
}

.child {
  padding: 1rem;
}

.container {
  border: 1px solid #2b7de0;
  display: flex;
  gap: 1rem;
  align-content: stretch;
  flex-wrap: wrap;
  height: 16rem;
  padding: 0.5rem;
}

.child {
  padding: 1rem;
}

Edit the code or use the selectors: the result updates instantly.