The flex-flow property in CSS is a shorthand that lets you set both the flex-direction and flex-wrap properties in a single line. This shorthand is especially useful for quickly controlling how flex items are laid out and whether they wrap or not.

The syntax for flex-flow is simple: write the direction first, followed by the wrap value, separated by a space. For example, flex-flow: row wrap; applies a horizontal layout with wrapping, while flex-flow: column nowrap; arranges items vertically without wrapping. Use cases for flex-flow include situations where you want to define both the main axis direction and the wrapping behavior together, making your CSS more concise and easier to read.

Using flex-flow in your CSS, as shown above, simplifies your code by combining two properties into one. Instead of writing:

.container {
  flex-direction: column;
  flex-wrap: wrap;
}

you can write:

.container {
  flex-flow: column wrap;
}