css - Aligning grid items across the entire row/column (like flex items can)

Question

With a flex container and flex-wrap: wrap set you can align overflowing items to the center using justify-content: center.

Is there a way to achieve the same behaviour for overflowing grid items using CSS grid?

I've created a pen showing the desired flex behavior

.container-flex {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
}

.container-flex .item {
  width: 33.33%;
  background: green;
  border: 1px solid;
}

.container-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
}

.container-grid .item {
  background: red;
  border: 1px solid;
}

* {
  box-sizing: border-box;
}

<h3>Flex</h3>
<div class="container-flex">
  <div class="item">item</div>
  <div class="item">item</div>
  <div class="item">item</div>
  <div class="item">item</div>
  <div class="item">item</div>
  <div class="item">item</div>
  <div class="item">item</div>
</div>

<h3>Grid</h3>
<div class="container-grid">
  <div class="item">item</div>
  <div class="item">item</div>
  <div class="item">item</div>
  <div class="item">item</div>
  <div class="item">item</div>
  <div class="item">item</div>
  <div class="item">item</div>
</div>

Answer 1

Flex and Grid are different animals, so a behavior that's simple in flex may not translate well to grid.

A flex item can center across the container because flex layout works with flex lines. A flex line is a row or column.

When a flex item is asked to center in a row/column, it has access to the available space on the entire line, from beginning to end.

In grid layout, however, rows and columns have to contend with something that flex lines don't: track walls (a/k/a grid lines). For example, in your code there are three columns. These columns divide the track into three separate sections, and grid items are confined to a section.

Therefore, a grid item cannot automatically be centered on a row using keyword alignment properties (such as justify-content or justify-self) because the track walls restrict movement.

It is possible to make a grid area span the entire row/column, which then clears the way across the entire track, allowing a grid item to be centered horizontally (justify-content: center) or vertically (align-self: center), but this behavior must be explicitly defined.

For the grid item to be centered across the row in a dynamic layout the container would need to have only one column (i.e., no dividers), or the item would need to be explicitly moved to the center using something like line-based placement. Otherwise, use flexbox.