How to Use CSS z-index: A Beginner's Guide

How to Use CSS z-index: A Beginner's Guide
Satyam Chaudhary
Web Development Jul 01, 2024

Have you ever wondered how web designers control which elements appear over others on a web page?

The answer lies in a powerful CSS property called z-index.

This beginner's guide will walk you through the basics of the z-index and show you how to use it to manage the order of overlapping elements, create visually appealing layouts, and troubleshoot common problems.

Let's dive in and unlock the potential of z-index in your web designs!

What is z-index?

Before diving into the practical aspects, it is important to understand what z-index actually is. This property plays a key role in web design by controlling the layering of elements.

So, what exactly is z-index?


The z-index property determines the overlap order of positioned elements those with a position value other than static.

Elements with a higher z-index value will always be stacked before elements with a lower value.

This is especially useful when you want to ensure that certain elements, such as popups or modals, appear above all other content.

CSS z-index Property

Now that we know what z-index is, let's get into the specifics of how it works. The syntax for z-index is straightforward, but mastering it can greatly enhance your web designs.


The syntax of the z-index property is simple and intuitive. Here’s how you can apply it in your CSS

In this syntax, the value is a numeric integer that determines the stacking order.

The higher the number, the closer the element is to the viewer, making it appear in front of elements with lower z-index values.

This simplicity makes it a powerful tool in your CSS toolkit.

Using the z-index property

Understanding the syntax is just the first step. Knowing how to effectively use the z-index in your projects is what will really set your designs apart.

Let's discuss how you can apply this property to your elements. Usage The z-index property applies to positioned elements.

These are elements that have their position set to relative, absolute, fixed or sticky. By default, elements have a z-index of auto, which means that their overlap order is determined by their position in the flow of the HTML document.

However, by assigning specific z-index values, you gain precise control over which elements appear above others, allowing for more complex and visually appealing designs.

Understanding z-index with examples

Example 1: Basic Usage

To see z-index in action, consider the following simple example:

Element A
Element B
fig 1:Example 1

In this example, Box B is positioned above Box A because it has a higher z-index value (2) compared to Box A (1). This demonstrates how the z-index property controls the stacking order of elements with overlapping positions.

Example 2: Complex Stacking Contexts

Child A
Child B
fig 2:Example 2

In this example, both Child A and Child B are positioned within the same parent stacking context. Child A has a higher z-index value (2) compared to Child B (1), so it appears above Child B. This demonstrates how z-index values work within nested elements, allowing you to manage the stacking order even in more complex layouts.

Explore common questions in our FAQ section: Interested in mastering the complexities of CSS z-index?

Dive into our FAQ section for answers to frequently asked questions.

z-index FAQs

  1. What happens when two elements have the same z-index?

    Answer: If two or more elements share the same parent and have the same z-index value, their overlap order will be determined by their order in the HTML source. The element written later in the HTML will appear on top.

  2. Can z-index be applied to un positioned elements?

    Answer: No, the z-index property only applies to elements with a defined position (position: relative, position: absolute, position: fixed, or position: sticky). Unplaced elements will ignore the z-index.

  3. How can I debug z-index issues in my layout?

    Answer: Use the browser's developer tools to inspect elements and their composition contexts. Check the calculated z-index values ??to ensure that the elements are correctly placed in their intended composition context.


Understanding and effectively using the z-index property is essential to creating layered and visually appealing web layouts. By mastering its concepts, syntax, and practical application, you can improve your ability to master element composition in CSS.

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Satyam Chaudhary

Satyam is a brilliant Engineering Undergraduate and proud Indian. He is passoinate towards web development and acquiring new skills.

He help students in understanding the concepts with a correct approach and solve their academic problems.

We are here to clear your doubts with an easy step by step approach.