In a recent project, I encountered a layout issue that was elegantly solved by the CSS Grid property grid-auto-flow: column. Let's dive into the problem and the solution.

The Problem

I was working on a responsive design where I needed to display a set of data items. On smaller screens, these items should stack vertically, but on larger screens, they should arrange themselves into a grid. The catch was, I wanted the items to fill up the columns first before moving on to the next row.

The default behavior of CSS Grid is to fill up the rows first (row-based placement), which wasn't what I wanted. Here's a simplified version of my initial CSS:

<section class="data">
  <div class="data__item">Item 1</div>
  <div class="data__item">Item 2</div>
  <div class="data__item">Item 3</div>
  <div class="data__item">Item 4</div>
  <div class="data__item">Item 5</div>
  <div class="data__item">Item 6</div>
</section>

.data {
  display: grid;
  gap: var(--space-m);
  grid-template-columns: repeat(2, auto);
  grid-template-rows: repeat(3, auto);
}

This render this layout:

The Solution

Enter grid-auto-flow: column. This property alters the default behavior of CSS Grid, making it fill up the columns before the rows (column-based placement). Here's how I modified my CSS:

.data {
  display: grid;
  gap: var(--space-m);
  grid-template-columns: repeat(2, auto);
  grid-template-rows: repeat(3, auto);

  /* Add this property 👇🏽 */
  grid-auto-flow: column;
}

With grid-auto-flow: column, the grid items now fill up vertically in each column before moving on to the next column. This was exactly the behavior I needed for my layout.

Conclusion

CSS Grid's grid-auto-flow: column is a powerful tool for controlling the placement of grid items. It's a great example of how a single CSS property can drastically simplify a complex layout problem. Happy coding!

More info

MDN: https://developer.mozilla.org/en-US/docs/Web/CSS/grid-auto-flow

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