Using z-index
The first part of this article, Stacking without the z-index property, explains how stacking is arranged by default. If you want to create a custom stacking order, you can use the z-index
property on a positioned element.
The z-index
property can be specified with an integer value (positive, zero, or negative), which represents the position of the element along the z-axis. If you are not familiar with the z-axis, imagine the page as a stack of layers, each one having a number. Layers are rendered in numerical order, with larger numbers above smaller numbers.
- bottom layer (farthest from the observer)
- ...
- Layer -3
- Layer -2
- Layer -1
- Layer 0 (default rendering layer)
- Layer 1
- Layer 2
- Layer 3
- ...
- top layer (closest to the observer)
Note:
- When no
z-index
property is specified, elements are rendered on the default rendering layer 0 (zero). - If several elements share the same
z-index
value (i.e., they are placed on the same layer), stacking rules explained in the section Stacking without the z-index property apply.
In the following example, the layers' stacking order is rearranged using z-index
. The z-index
of element #5 has no effect since it is not a positioned element.
Source code for the example
HTML
<div id="abs1">
<b>DIV #1</b>
<br />position: absolute;
<br />z-index: 5;
</div>
<div id="rel1">
<b>DIV #2</b>
<br />position: relative;
<br />z-index: 3;
</div>
<div id="rel2">
<b>DIV #3</b>
<br />position: relative;
<br />z-index: 2;
</div>
<div id="abs2">
<b>DIV #4</b>
<br />position: absolute;
<br />z-index: 1;
</div>
<div id="sta1">
<b>DIV #5</b>
<br />no positioning
<br />z-index: 8;
</div>
CSS
div {
padding: 10px;
opacity: 0.7;
text-align: center;
}
b {
font-family: sans-serif;
}
#abs1 {
z-index: 5;
position: absolute;
width: 150px;
height: 350px;
top: 10px;
left: 10px;
border: 1px dashed #900;
background-color: #fdd;
}
#rel1 {
z-index: 3;
height: 100px;
position: relative;
top: 30px;
border: 1px dashed #696;
background-color: #cfc;
margin: 0px 50px 0px 50px;
}
#rel2 {
z-index: 2;
height: 100px;
position: relative;
top: 15px;
left: 20px;
border: 1px dashed #696;
background-color: #cfc;
margin: 0px 50px 0px 50px;
}
#abs2 {
z-index: 1;
position: absolute;
width: 150px;
height: 350px;
top: 10px;
right: 10px;
border: 1px dashed #900;
background-color: #fdd;
}
#sta1 {
z-index: 8;
height: 70px;
border: 1px dashed #996;
background-color: #ffc;
margin: 0px 50px 0px 50px;
}
See also
- Stacking without the z-index property: The stacking rules that apply when
z-index
is not used. - Stacking with floated blocks: How floating elements are handled with stacking.
- The stacking context: Notes on the stacking context.
- Stacking context example 1: 2-level HTML hierarchy, z-index on the last level
- Stacking context example 2: 2-level HTML hierarchy, z-index on all levels
- Stacking context example 3: 3-level HTML hierarchy, z-index on the second level