Why Does Content Extend Beyond Rounded Corners in Web Design?

Rounded Corners and Content Clipping: Expected or Unexpected?

In web design, the use of rounded corners (border-radius) is often desired to create visually appealing layouts. However, a puzzling issue arises when content seems to extend beyond the rounded edges of its container.

Case in Point:

Consider the following HTML and CSS:

In this example, the div with class "progressbar" has rounded corners, but the div within it ("buffer") appears to break free from these constraints and extends outside the curved edges.

The Truth Revealed:

Surprisingly, this behavior is intended by web browsers. According to the CSS specification, the default overflow value for elements (including divs) is "visible," which allows content to extend beyond the element's borders.

The "border-radius" property, however, only affects the background of the element and does not clip its content. To clip content to the curved borders, the overflow value must be set to a value other than "visible," such as "hidden" or "scroll."

Solution Nirvana:

To resolve this issue, simply set the overflow property of the container ("progressbar") to "hidden," as seen in this modified snippet:

By doing so, the content within the container will be properly clipped to the curved edges, giving you the desired visual effect.

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