mozilla
Your Search Results

    z-index

    Summary

    The z-index 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:

    1. The stack level of the box in the current stacking context.
    2. Whether the box establishes a local stacking context.

    Syntax

    /* Keyword value */
    z-index: auto;
    
    /* <integer> values */
    z-index: 0;
    z-index: 3;
    z-index: 289;
    
    z-index: inherit
    

    Values

    auto
    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.
    <integer>
    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.

    Formal syntax

    auto | <integer>
    

    Examples

    HTML

    <div class="dashed-box">Dashed box
      <span class="gold-box">Gold box</span>
      <span class="green-box">Green box</span>
    </div>
    

    CSS

    .dashed-box { 
      position: relative;
      z-index: 1;
      border: dashed;
      height: 8em;
      margin-bottom: 1em;
      margin-top: 2em;
    }
    .gold-box { 
      position: absolute;
      z-index: 3; /* put .gold-box above .green-box and .dashed-box */
      background: gold;
      width: 80%;
      left: 60px;
      top: 3em;
    }
    .green-box { 
      position: absolute;
      z-index: 2; /* put .green-box above .dashed-box */
      background: lightgreen;
      width: 20%;
      left: 20em;
      top: -25px;
      height: 7em;
      opacity: 0.9;
    }
    

    Result

     

    Specifications

    Specification Status Comment
    CSS Transitions
    The definition of 'animation behavior for z-index' in that specification.
    Working Draft Defines z-index as animatable.
    CSS Level 2 (Revision 1)
    The definition of 'z-index' in that specification.
    Recommendation Initial specification.

    Browser compatibility

    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
    Basic support ? ? ? ? ?

    See also

    Hide Sidebar