Understanding the Z-Index in CSS: A Comprehensive Guide

The z-index is a powerful property in Cascading Style Sheets (CSS) that can control the stack order of positioned elements. This tutorial will walk you through its usage, providing examples to help you understand how it works.

What is Z-Index?

In CSS, every element on a webpage has three dimensions: height, width, and depth. The ‘z-index’ property controls the third dimension – depth. It determines which elements appear in front and which ones go behind when they overlap.

How Does Z-Index Work?

Z-index only works on positioned elements. These are elements with their position set to relative, absolute or fixed. The z-index value can be positive or negative integers. Elements with a higher z-index value are displayed in front of those with a lower one.

#element1 {
  position: absolute;
  z-index: 1;

#element2 {
  position: absolute;
  z-index: 2;

In this example, element2 will appear above element1 because it has a higher z-index value.

Using Z-Index Properly

To use z-index effectively:

  • Position your elements: Remember that z-index only affects positioned elements (relative, absolute or fixed).
  • Avoid high values: Using unnecessarily high values like 9999 can lead to management issues later on. Stick to small increments like 1, 2, 3 etc.
  • Negative values: You can use negative values if you want an element to appear below others.


The z-index property is a powerful tool in CSS that can help you control the layering of elements on your webpage. With careful use, it can greatly enhance the user experience by ensuring that important elements are always visible and interactive.

Remember to keep practicing with different values and positions to get a better understanding of how z-index works. Happy coding!

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