CSS - z-index Property

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CSS z-index property is used to control the stacking order of elements in a web page when they overlap in the same stacking context. Elements with a higher z-index value appear in front of elements with lower values.

The following diagram demonstrates the z-index layout for reference:

z-index

The z-index property can be used with positioned elements that are nested inside of other positioned elements.

Possible Values

  • auto − The default value. The stack order is equal to that of the parent element.

  • <Integer> − A positive or negative integer. It sets the element's stack level to the given value.

Applies to

All positioned elements.

DOM Syntax

object.style.zIndex = "2";

CSS z-index - auto Value

CSS z-index: auto sets the z-index of an element to its parent element's stack order. It is the default value for the z-index property.

<html>
<head>
<style>
   .box1 {
      position: absolute;
      height: 200px;
      width: 280px;
      background-color: #f0baba;
      z-index: auto;
      text-align: center;
      padding: 3px;
      left: 10px;
      top: 10px;
   }
   .box2 {
      position: absolute;
      height: 120px;
      width: 200px;
      background-color: #eae98f;
      z-index: 1;
      text-align: center;
      padding: 5px;
      margin: 20px;
      left: 30px;
      top: 30px;
   }
   p {
      margin-top: 250px;
   }
</style>
</head>
<body>
   <p>The element with z-index value of auto appears behind the element with the z-index value of 1.</p>
   <div class="box1">
      <span>CSS z-index: auto</span>
      <div class="box2">
         <span>CSS z-index: 1</span>
      </div>
   </div>
   
</body>
</html>

CSS z-index - with Positive Integer

CSS z-index property can have a positive integer value. The element with a higher integer value will appear above elements with lower values in the stacking order.

<html>
<head>
<style>
   .box1 {
      position: absolute;
      height: 200px;
      width: 280px;
      background-color: #f0baba;
      z-index: 1;
      text-align: center;
      padding: 3px;
      left: 10px;
      top: 10px;
   }
   .box2 {
      position: absolute;
      height: 140px;
      width: 220px;
      background-color: #eae98f;
      z-index: 2;
      text-align: center;
      padding: 5px;
      margin: 10px;
      left: 30px; 
      top: 30px;
   }
   .box3 {
      position: absolute;
      height: 90px;
      width: 160px;
      background-color: #b7c8ae;
      z-index: 3;
      text-align: center;
      padding: 5px;
      margin: 20px;
      left: 50px; 
      top: 50px;
   }
   p {
      margin-top: 250px;
   }
</style>
</head>
<body>
   <p>The element with z-index value of 1 appears behind the element with the z-index value of 2 and 3.</p>
   <div class="box1">
      CSS z-index: 1
   </div>
   <div class="box2">
      CSS z-index: 2
   </div>
   <div class="box3">
      CSS z-index: 3
   </div>
</body>
</html>

CSS z-index - With Negative Integer

You can also use negative integer values for the z-index property. An element with a negative z-index value will be stacked below elements with a higher z-index value.

<html>
<head>
<style>
   .box1 {
      position: absolute;
      height: 200px;
      width: 280px;
      background-color: #f0baba;
      z-index: -3;
      text-align: center;
      padding: 3px;
      left: 10px; 
      top: 10px;
   }
   .box2 {
      position: absolute;
      height: 140px;
      width: 220px;
      background-color: #eae98f;
      z-index: -2;
      text-align: center;
      padding: 5px;
      margin: 10px;
      left: 30px; 
      top: 30px;
   }
   .box3 {
      position: absolute;
      height: 90px;
      width: 160px;
      background-color: #b7c8ae;
      z-index: -1;
      text-align: center;
      padding: 5px;
      margin: 20px;
      left: 50px; 
      top: 50px;
   }
   p {
      margin-top: 250px;
   }
</style>
</head>
<body>
   <p>The element with z-index value of -3 appears behind the element with the z-index value of -2 and -1.</p>
   <div class="box1">
      CSS z-index: -3
   </div>
   <div class="box2">
      CSS z-index: -2
   </div>
   <div class="box3">
      CSS z-index: -1
   </div>
</body>
</html>

CSS z-index - With Sticky Position

The following example demonstrates how the z-index property can be used to control the stacking order of elements with the position: sticky property, so that they stay fixed in place as the page scrolls −

<html>
<head>
<style>
   .box1 {
      position: sticky;
      height: 200px;
      width: 280px;
      background-color: #f0baba;
      z-index: 1;
      text-align: center;
      padding: 3px;
      margin: 10px;
      left: 10px; 
      top: 80px;
   }
   .box2 {
      position: sticky;
      height: 140px;
      width: 220px;
      background-color: #eae98f;
      z-index: 2;
      text-align: center;
      padding: 5px;
      margin: 10px;
      left: 40px; 
      top: 200px;
   }
   .box3 {
      position: sticky;
      height: 90px;
      width: 160px;
      background-color: #b7c8ae;
      z-index: 3;
      text-align: center;
      padding: 5px;
      margin: 10px;
      left: 70px; 
   } 
</style>
</head>
<body>
   <p>Move cursor upward to see the effect.</p>
   <div class="box1">
      CSS z-index: 1
   </div>
   <div class="box2">
      CSS z-index: 2
   </div>
   <div class="box3">
      CSS z-index: 3
   </div>
</body>
</html>

CSS z-index - With Fixed Position

The following example demonstrates how to use the z-index property to make an element stay on top of the content when the user scrolls down, even if it has the position: fixed property −

<html>
<head>
<style>
   .container {
      position: relative;
      height: 350px;
   }
   .box1 {
      position: fixed;
      height: 200px;
      width: 280px;
      background-color: #f0baba;
      z-index: -3;
      text-align: center;
      padding: 3px;
      left: 10px; 
      top: 10px;
   }
   .box2 {
      position: fixed;
      height: 140px;
      width: 220px;
      background-color: #eae98f;
      z-index: -2;
      text-align: center;
      padding: 5px;
      margin: 10px;
      left: 30px; 
      top: 30px;
   }
   .box3 {
      position: fixed;
      height: 90px;
      width: 160px;
      background-color: #b7c8ae;
      z-index: -1;
      text-align: center;
      padding: 5px;
      margin: 20px;
      left: 50px; 
      top: 50px;
   }
   h3 {
         margin-top: 320px;
   }
</style>
</head>
<body>
   <h3>Scroll down the content to see the effect.</h3>
   <div class="container">
      <div class="box1">
         CSS z-index: -3
      </div>
      <div class="box2">
         CSS z-index: -2
      </div>
      <div class="box3">
         CSS z-index: -1
      </div>
   </div>
</body>
</html>

CSS z-index - With Static Position

The following example shows that the z-index property does not affect the stacking order of elements that have the position: static property −

<html>
<head>
<style>
   .box1 {
      position: static;
      height: 200px;
      width: 280px;
      background-color: #f0baba;
      z-index: 1;
      text-align: center;
      padding: 3px;
      margin: 10px;
      left: 10px;
      top: 10px;
   }
   .box2 {
      position: static;
      height: 140px;
      width: 220px;
      background-color: #eae98f;
      z-index: 2;
      text-align: center;
      padding: 5px;
      margin: 10px;
      left: 30px; 
      top: 30px;
   }
   .box3 {
      position: static;
      height: 90px;
      width: 160px;
      background-color: #b7c8ae;
      z-index: 3;
      text-align: center;
      padding: 5px;
      margin: 10px;
      left: 50px; 
      top: 50px;
   }
</style>
</head>
<body>
   <p>The z-index property has no effect on the stacking order of elements if the position property is set to static.</p>
   <div class="box1">
      CSS z-index: 1
   </div>
   <div class="box2">
      CSS z-index: 2
   </div>
   <div class="box3">
      CSS z-index: 3
   </div>
</body>
</html>

CSS z-index - With Relative Position

The example shows that when elements have the position: relative property, the z-index property positions the element relative to its original position in the document flow.

<html>
<head>
<style>
   .box1 {
      position: relative;
      height: 200px;
      width: 280px;
      background-color: #f0baba;
      z-index: 1;
      text-align: center;
      padding: 3px;
      margin: 10px;
      left: 10px;
      top: 10px;
   }
   .box2 {
      position: relative;
      height: 140px;
      width: 220px;
      background-color: #eae98f;
      z-index: 2;
      text-align: center;
      padding: 5px;
      margin: 10px;
      left: 30px; 
      top: 30px;
   }
   .box3 {
      position: relative;
      height: 90px;
      width: 160px;
      background-color: #b7c8ae;
      z-index: 3;
      text-align: center;
      padding: 5px;
      margin: 10px;
      left: 50px; 
      top: 50px;
   }
</style>
</head>
<body>
   <p>The z-index property positions the element relative to its original position if position is relative.</p>
   <div class="box1">
      CSS z-index: 1
   </div>
   <div class="box2">
      CSS z-index: 2
   </div>
   <div class="box3">
      CSS z-index: 3
   </div>
</body>
</html>
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