z-index
Definition
z-index controls which suitable web elements appear in front of others within a stacking context.
A CSS property that influences the stacking order of positioned or suitable elements within stacking contexts.
Simply explained
When elements on a webpage overlap, z-index helps determine the order of their layers. This applies within their shared stacking context.
Why it matters in practice
The term contributes to secure, maintainable, and high-performance web applications as well as resilient technical decisions.
Example from business
A dialog appears above navigation and overlay without changing focus order or semantics.
Limits and pitfalls
- A high value does not override a foreign stacking context; visual order does not replace DOM or focus logic.
Origin & history
z-index has been part of the visual layering of web content since early CSS versions.
Use in mid-sized companies
- Possible example: A dialog appears above navigation and overlay without changing focus order or semantics.
Frequently asked questions
What does z-index mean?
A CSS property that influences the stacking order of positioned or suitable elements within stacking contexts. What should you watch out for? A high value does not override a foreign stacking context; visual order does not replace DOM or focus logic.
Sources
- CSS Positioned Layout Module Level 3 · W3C, CSS Positioned Layout Module Level 3
Source checked on 10.10.2026. Editorial usage examples are hypothetical; no proof of real customer results.
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