What does a higher z-index value indicate?

A higher z-index value indicates that the element will be positioned on top of elements with lower z-index values in the stacking order. The z-index is a CSS property that controls the vertical stacking order of elements that overlap. When two or more elements overlap, the one with the higher z-index will be rendered on top, making it visible to the user rather than obscured by other elements. This property is critical in web design, particularly when creating complex layouts, modal dialogs, or dynamic user interfaces where the visual hierarchy of elements needs to be controlled effectively.

In contrast, lower z-index values will stack behind those with higher values, which is essential to understand for ensuring that important elements remain visible and accessible to users. Elements without a specified z-index default to a z-index of auto, thereby relying on the order in which they appear in the HTML markup. Hence, understanding how z-index works is crucial for managing visibility in web design.