CSS Grid vs Flexbox: When to Use Which

CSS Grid and Flexbox are both powerful layout systems, but they solve different problems. Choosing the wrong one leads to overcomplicated CSS, fragile layouts, and frustrating workarounds. This guide covers when to use each, with practical examples from real-world projects.

The Core Difference

Flexbox is one-dimensional — it handles layout in a single direction (row or column) at a time. Grid is two-dimensional — it handles rows and columns simultaneously. This fundamental difference determines which tool fits each layout problem.

Think of Flexbox as laying out items along a line. Think of Grid as placing items on a grid. When your layout naturally flows in one direction with wrapping, use Flexbox. When your layout needs precise two-dimensional placement, use Grid.

When to Use Flexbox

Flexbox is the right choice for navigation bars (items flowing horizontally with variable spacing), button groups (aligned buttons with consistent gaps), card rows (horizontally scrolling or wrapping card lists), centering content (both vertically and horizontally), form layouts (label-input pairs in a row), and any component where items flow in one direction.

The classic Flexbox pattern is a navigation bar: display flex, justify-content space-between, align-items center. The logo sits on the left, navigation links in the middle, and action buttons on the right. Flexbox handles this naturally because it is a single-row layout with variable spacing.

Another common pattern is centering: display flex, justify-content center, align-items center, min-height 100vh. This centers any content both horizontally and vertically in the viewport — something that was notoriously difficult before Flexbox.

When to Use Grid

Grid is the right choice for page layouts (header, sidebar, main content, footer), card grids (equal-sized cards in rows and columns), dashboard layouts (widgets of different sizes arranged in a grid), image galleries (masonry or equal-grid layouts), form layouts (complex multi-column forms), and any layout that requires alignment on both axes.

The classic Grid pattern is a page layout: display grid, grid-template-columns 250px 1fr, grid-template-rows auto 1fr auto. This creates a sidebar layout with header and footer that would require nested Flexbox containers and fragile calculations to achieve otherwise.

For responsive card grids, the auto-fill pattern is powerful: grid-template-columns repeat(auto-fill, minmax(300px, 1fr)). This creates a grid that automatically adjusts the number of columns based on available space — no media queries needed. Cards fill available space with a minimum width of 300 pixels.

Combining Grid and Flexbox

The best layouts use both. Grid handles the macro layout (page structure, content areas), and Flexbox handles the micro layout (content within grid cells). A dashboard might use Grid for the overall widget layout and Flexbox inside each widget for header alignment and content flow.

This combination is not a compromise — it is the intended usage. Grid and Flexbox were designed to complement each other. Using Grid for everything or Flexbox for everything leads to awkward workarounds.

Common Mistakes

Using Flexbox for two-dimensional grids is the most common mistake. Developers create a Flexbox container with flex-wrap and calculate widths with percentages or calc to simulate a grid. This works but is fragile — Grid handles this natively with fewer lines of CSS and better alignment guarantees.

Using Grid for simple one-directional layouts adds unnecessary complexity. A horizontal navigation bar does not need Grid. Flexbox handles it with less code and clearer intent.

Not using the gap property is another missed opportunity. Both Grid and Flexbox support the gap property for consistent spacing between items. It replaces margin hacks and :last-child overrides with a single, clean declaration.

Performance Considerations

Both Grid and Flexbox perform well in modern browsers. Grid layout calculations are slightly more expensive because the browser resolves two-dimensional constraints, but the difference is negligible for typical page layouts. The performance issue to watch for is excessive re-layout — avoid layouts where changing one element forces the browser to recalculate the entire grid. Use fixed or fractional track sizes rather than content-based sizing for performance-critical grids.

Browser Support

As of 2026, CSS Grid and Flexbox are supported in all modern browsers with no vendor prefixes needed. The subgrid feature (allowing nested grids to align with the parent grid) is now supported in Chrome, Firefox, and Safari. Container queries complement both Grid and Flexbox by allowing responsive behavior based on component size rather than viewport size.

Quick Decision Guide

If items flow in one direction: Flexbox. If you need alignment on both axes: Grid. If you are centering something: Flexbox. If you are making a page-level layout: Grid. If you are making a card grid: Grid with auto-fill. If you are making a toolbar: Flexbox. If you are not sure: start with Flexbox, switch to Grid when you find yourself fighting it.