Why Doesn't Vertical-Align Center Inline-Block Elements Within Their Containers?

Understanding Vertical Alignment for Inline-Block Elements

While documentation suggests that vertical alignment works for inline-block elements, it can be confusing when it fails to align as expected. To clarify, let's delved deeper into the concept.

Vertical-Align's Scope

Unlike text-align, which adjusts text alignment within its parent element's content area, vertical-align operates within the element's line box. A line box is the rectangular area that encompasses the boxes generated by an inline-level element on a single line.

Example:

Consider the following code:

#wrapper {
  border: 1px solid black;
  width: 500px;
  height: 500px;
}
#content {
  border: 1px solid black;
  display: inline-block;
  vertical-align: middle;
}

<div>

Problem:

In this example, setting vertical-align: middle does not vertically center the #content element within the #wrapper div.

Explanation:

Vertical-align does not align the inline-block element relative to its container block but rather within its own line box. Since the #content element contains only text, which is already vertically centered based on its default vertical-align: baseline, it has no effect on the final alignment.

Conclusion:

When working with vertical alignment for inline-block elements, it's essential to understand that it aligns content within the element's line box, not its containing block. Keep this in mind to achieve the desired vertical positioning in your page elements.

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