Does Flexbox Eliminate Margin Collapsing?

Margin Collapsing in Flexbox

In CSS, when a parent and its last child both have margins, those margins collapse into a single margin. However, this behavior changes when using flexbox.

In flexbox, margins do not collapse. This means that the margin on a flex item's parent element (e.g., a flex container) will not combine with the margin on the flex item itself. This can result in unintended spacing between elements in a flexbox layout.

For example, consider the following CSS:

article {
  margin-bottom: 20px;
}

main {
  background: pink;
  margin-bottom: 20px;
}

footer {
  background: skyblue;
}

In this example, we have an article element nested inside a main element, which is in turn nested inside a footer element. Without flexbox, the margin on the article and the margin on the main would collapse into a single margin of 20px between the article and the footer. However, with flexbox, we get a 40px margin between the article and the footer—a full 20px margin from the article to main, and another 20px from main to footer.

To prevent this behavior, we can remove the flexbox layout from the container element. For example:

#container {
  display: block;
}

By setting the display property of the container element to block, we remove the flexbox formatting context and restore the default margin collapsing behavior.

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