How to Stretch a Flex Child to Fill the Parent\'s Height Without Setting Parent Height?

Stretching Flex Child to Fill Container Height without Setting Parent Height

When attempting to stretch a yellow flex child to fill the entire height of its parent container, it's crucial to avoid setting the parent height. Instead, the parent height should dynamically adjust based on the content of the blue child.

A common pitfall when working with Flexbox is the excessive use of height: 100%. While this is often necessary in other contexts, it can disrupt Flexbox layout.

Reason 1: Parent Height Dependency

When using height: 100%, the parent of the element being stretched also requires a defined height, which Flexbox doesn't necessitate in most cases. This can lead to unexpected behavior.

Reason 2: Neglect of Sibling Elements

If the flex child has siblings above or below it, using height: 100% will neglect their presence, potentially causing layout issues.

Solution: Remove height: 100%

The solution is straightforward: Remove height: 100% from the yellow flex child. This allows the default behavior of Flexbox to take over.

Default Flexbox Behavior

For flex items arranged in a horizontal row (the default), align-items controls their vertical alignment. By default, this is set to stretch, which automatically fills the height of the container.

Code Sample

<code class="html"><div style='display: flex'>
  <div style='background-color: yellow; width: 20px'></div>
  <div style='background-color: blue'>
    some<br>
    cool<br>
    text
  </div>
</div></code>

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