Definition and Usage
The z-index CSS property specifies the z-order of an element and its descendants. When elements overlap, z-order determines which one covers the other. An element with a larger z-index generally covers an element with a lower one.
For a positioned box, the z-index property specifies:
- The stack level of the box in the current stacking context.
- Whether the box establishes a local stacking context.
- Initial auto
- Applies to positioned elements
- Inherited no
- Media visual
- Computed Value as specified
- Animatable yes, as an integer
- Canonical order the unique non-ambiguous order defined by the formal grammar
Formal syntax: auto | <integer>
z-index: auto /* Keyword value */ z-index: 0 /* <integer> value */ z-index: 3 z-index: 289 z-index: inherit
- The box does not establish a new local stacking context. The stack level of the generated box in the current stacking context is the same as its parent's box.
- This integer is the stack level of the generated box in the current stacking context. The box also establishes a local stacking context in which its stack level is 0. This means that the z-indexes of descendants are not compared to the z-indexes of elements outside this element.
|Feature||Chrome||Firefox (Gecko)||Internet Explorer||Opera||Safari|
|Basic support||1.0||1.0 (1.7 or earlier)||4.0||4.0||1.0|
|Negative values (CSS2.1 behavior, not allowed in the obsolete CSS2 spec)||1.0||3.0 (1.9)||4.0||4.0||1.0|
|Feature||Android||Firefox Mobile (Gecko)||IE Mobile||Opera Mobile||Safari Mobile|