cSS z-index property

The z-index property is used to control the stacking order of positioned elements within a webpage. Essentially, it determines the order in which elements are displayed on the z-axis, with a higher z-index value bringing an element to the forefront.

In the below PDF we discuss about  CSS z-index  in detail in simple language, Hope this will help in better understanding.


Basics of z-index:

The syntax for the z-index property is relatively straightforward:

selector {
z-index: value;

Here, the value can be any integer, positive or negative, representing the stacking order of the element. The higher the value, the closer the element is to the user, and vice versa.

Stacking Context:
Understanding the stacking context is crucial to mastering the z-index property. Each element in a document creates a stacking context, and the stacking order is determined within this context. When an element’s z-index is set, it affects the stacking order of its children within the same stacking context.

Creating a Stacking Context:
Several factors can create a stacking context, including:

Elements with a position value of absolute or relative and a z-index value other than auto.
Positioned and flex container elements with a z-index value other than auto.
Elements with an opacity value less than 1.


1.  Overlapping Elements:
One common scenario where the z-index property is employed is when dealing with overlapping elements. By strategically setting the z-index values, you can control which element appears on top in the stacking order.

.box1 {
position: absolute;
z-index: 2;

.box2 {
position: absolute;
z-index: 1;

In this example, box1 would appear above box2 on the z-axis.

2. Layered Navigation Menus:
Navigation menus with dropdowns are another area where the z-index property proves invaluable. By adjusting the z-index values of the navigation and dropdown elements, you can ensure that dropdowns appear above other page elements.

.nav-menu {
position: relative;
z-index: 1;

.dropdown {
position: absolute;
z-index: 2;

Related Question

The z-index property in CSS is used to control the stacking order of positioned elements along the z-axis (depth).

Elements with a higher z-index value are positioned in front of elements with lower values. If two elements have the same z-index, the one appearing later in the HTML code will be on top.

The z-index property accepts integer values and the keyword auto. Positive integers represent higher stacking order, while negative integers and auto have special meanings for default stacking.

No, the z-index property only applies to positioned elements. Elements need to have a positioning value other than static (e.g., relative, absolute, or fixed) for z-index to take effect.


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