z-index
z-index is a CSS property that sets the front-to-back level of a positioned box. In some cases, it also creates a new local stacking context.
Another example
An overlay, popover, and header use planned layer values inside known stacking contexts. Each appears in the intended local order. Z-index cannot escape a parent's stacking context or fix an element placed under the wrong DOM owner.
Main parts
- 01positioned box
- 02stack level
- 03applicable context
Use it when
Use this term to set a planned layer after finding the stacking context that controls it.
Do not use it when
Do not keep raising random numbers before checking how contexts are made and how elements are ordered in the source.
Name used in code
z-index: <integer> | auto Before you ship
Check content order, shared design values, component consistency, contrast, zoom, and layout changes by screen size. Verify every theme, language, and state. If there is motion, offer an equal reduced-motion experience.
Outcome: Use or define z-index to make the visual experience clear and easy to use. User context: An overlay, popover, and header use planned layer values inside known stacking contexts. Each appears in the intended local order. Z-index cannot escape a parent's stacking context or fix an element placed under the wrong DOM owner. Design concept to apply: z-index. Why it fits: Use this term to set a planned layer after finding the stacking context that controls it. Do not use it when: Do not keep raising random numbers before checking how contexts are made and how elements are ordered in the source. Design requirements: Set the content order, shared design values, and reusable components. Define how the layout changes by screen size and state. Keep useful design choices separate from decoration. Inclusion and resilience: Check contrast, zoom, languages, themes, and reduced motion when needed. Do not use color or effects as the only way to show meaning. Acceptance criteria: The design stays clear on phones and desktops, at zoom, in every theme, and in all supported languages. Interactive states stay clear and consistent. Evidence and limits (evidence boundary): A formal document may still be a draft, release candidate, or final version. Check its status and browser or platform support. Unknowns to confirm: Brand limits, amount of content, supported themes and languages, target devices, and design-system rules.
Check this request
Review the current use of z-index. Definition: z-index is a CSS property that sets the front-to-back level of a positioned box. In some cases, it also creates a new local stacking context. Release checks: Check content order, shared design values, component consistency, contrast, zoom, and layout changes by screen size. Verify every theme, language, and state. If there is motion, offer an equal reduced-motion experience. Before changing code, report the evidence you found, gaps, severity, and the smallest safe fix.