CSS z-index Property
Sets the stack order of a positioned element and its descendants
Syntax
z-index: auto | <integer>;Values
| Value | Description |
|---|---|
| auto | Same stack order as parent |
| <integer> | Positive or negative stacking order |
| initial | Resets to default value |
| inherit | Inherits from parent |
Example
.modal-overlay {
position: fixed;
inset: 0;
z-index: 1000;
background: rgba(0, 0, 0, 0.5);
}Understanding CSS z-index
The CSS z-index property sets the stack order of a positioned element and its descendants. As part of the Layout module in CSS, it is one of the most commonly used properties for controlling the visual presentation of web pages.
You can set z-index to values such as auto, <integer>, initial, inherit, among others. Each value changes how the browser renders the affected element, giving you fine-grained control over your page layout and design. Choosing the right value depends on the specific design requirements of your project.
Common use cases for the z-index property include responsive web design, component-based layouts, and creating visually consistent interfaces across devices. It works closely with related properties like position, isolation, opacity to achieve complex styling effects. Understanding how these properties interact helps you write cleaner, more maintainable stylesheets.
Browser support for z-index is excellent across all modern browsers including Chrome, Firefox, Safari, and Edge. For older browsers, consider using fallback values or progressive enhancement strategies. The property can also be set dynamically via JavaScript using element.style.zIndex or the CSS custom properties (variables) approach for theming.
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