CSS Flexbox vs Grid: When to Use Each

The short answer to CSS Flexbox vs Grid: use Flexbox when you're lining things up in one direction, a row or a column, and want the content to decide the sizes. Use Grid when you need rows and columns at the same time, or when the layout should decide where things go. Most real pages use both: Grid for the overall layout and card lists, Flexbox for the small pieces inside them. Below I show how I decide, with code you can copy, plus the mistakes I made while learning both. I used to pick one at random and fight it until the layout worked.