The z-index property in CSS determines the stacking order of positioned elements. Specifically, it dictates which elements appear in front of or behind others on the z-axis, which represents depth on a three-dimensional plane.
Z-index only works on elements with a position other than static (i.e., absolute, relative, fixed, or sticky). It does not affect elements with a position of static or elements positioned using floats.
A stacking context is created when an element is positioned and has a z-index applied. Within a stacking context, the z-index property sets the stacking order of the positioned element and its descendants. Stacking contexts prevent elements in one context from interfering with the stacking order of elements in a different context.
The stacking order of elements without a z-index specified is as follows:
When a z-index property is applied, the stacking order is modified:
Mixed Sibling Result: div.sibling-2 will appear in front of div.sibling-1 because its z-index is higher. Nested div.container has position: static and z-index: 0 Result: div.sibling will appear in front of both child divs because it is positioned with a higher z-index in a different stacking context. The above is the detailed content of How Does CSS z-index Control the Stacking Order of HTML Elements?. For more information, please follow other related articles on the PHP Chinese website!