Paste CSS with z-index, position, opacity, transform, filter, or will-change rules.
Provide HTML to map class names to elements. Enables richer context in the output.
Ready to visualize
Paste CSS and click Analyze// visualize stacking contexts and z-index layers
Visualize CSS z-index stacking contexts and layer order instantly. Paste your CSS and HTML to debug overlap issues, identify stacking contexts, and fix z-index conflicts.
Paste CSS with z-index, position, opacity, transform, filter, or will-change rules.
Provide HTML to map class names to elements. Enables richer context in the output.
Ready to visualize
Paste CSS and click AnalyzeAdd CSS rules containing z-index, position, opacity, transform, filter, or will-change properties.
Provide the HTML structure to map selectors to element context for a richer analysis.
Get a visual stacking diagram, context tree, conflict warnings, and trigger breakdown instantly.
The CSS Z-Index Visualizer parses your CSS rules and builds a visual representation of how elements stack on the Z-axis. It detects stacking contexts — isolated z-index universes created by properties like opacity, transform, and will-change — and shows you exactly why one element renders above or below another.
A stacking context is a three-dimensional conceptual space where child elements are stacked according to their z-index values. Any element that forms a stacking context creates an isolated z-index universe — child elements can never visually escape outside it, no matter how high their z-index.
If an element is inside a stacking context with a lower z-index than a sibling context, the inner element can never appear above that sibling — regardless of its z-index value. The entire context is painted as a unit. This is the most common source of z-index confusion.
Many CSS properties trigger stacking contexts: position: fixed/sticky, opacity < 1, transform, filter, will-change, isolation: isolate, mix-blend-mode, contain: layout/paint, and elements with position + z-index != auto.
No. z-index only applies to positioned elements — those with position set to relative, absolute, fixed, or sticky. On a static element, z-index is ignored entirely. The visualizer flags these cases automatically.
First, identify whether the conflicting elements share the same stacking context. If not, fix the z-index of the ancestor contexts rather than the children. Use isolation: isolate to intentionally create stacking contexts for components, keeping z-index values contained and predictable.
isolation: isolate creates a new stacking context without any visual side effects (unlike opacity or transform). It is the cleanest way to scope z-index to a component, ensuring child elements never interfere with the global stacking order.
No. All analysis is performed entirely in your browser using JavaScript. Your CSS and HTML are never transmitted anywhere. The tool works fully offline once loaded.
Yes. Paste as many CSS rules as you need. The parser handles multiple selectors, grouped rules, and complex stylesheets. For very large files, consider filtering to only the relevant components to get a clearer, more focused visualization.
A CSS Z-Index Visualizer is a developer tool that parses CSS rules and renders a visual representation of how elements are ordered on the Z-axis — the imaginary axis that extends toward and away from the viewer. Rather than guessing why one element appears above or below another, a visualizer maps the entire stacking order and makes the underlying structure explicit.
Z-index is one of the most misunderstood CSS properties. On the surface it appears simple: higher number means closer to the viewer. In practice, the behavior is governed by stacking contexts — isolated painting layers that make z-index comparisons local rather than global. This tool surfaces those contexts and explains the exact reason each element appears where it does.
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A stacking context is a self-contained painting group. Within a context, child elements are ordered by their z-index. But crucially, that ordering is local — the entire context is treated as a single unit when compared to sibling contexts. This means a child element with z-index: 9999 can never appear above an element outside its ancestor context if that ancestor context has a lower z-index than its sibling.
Stacking contexts are created by a surprisingly large number of CSS properties. The most commonly encountered are position: fixed and position: sticky, but contexts are also created by any element with opacity less than 1, any element using transform, filter, clip-path, will-change, isolation: isolate, mix-blend-mode with a value other than normal, and elements using CSS containment with layout or paint values.
The most frequent z-index issue in production code is a modal or overlay that appears behind other page elements despite a very high z-index. This almost always means the modal is nested inside a stacking context that itself has a lower z-index than the element it needs to appear above. No amount of increasing the modal's z-index will fix this — the fix must happen at the ancestor level.
The second most common issue is tooltips or dropdown menus appearing beneath sibling components. Again, this is usually caused by the tooltip's parent creating a stacking context via a transform or opacity animation, isolating the tooltip inside a local z-index space. A common fix is to use CSS custom properties and JavaScript to manage z-index as a system, or to teleport tooltip elements to the document root using portals in component frameworks.
A third issue is the invisible stacking context: a transition or animation that temporarily applies a transform creates a stacking context for the duration of the animation. This can cause elements to flicker in and out of correct stacking order during interactions, which is notoriously difficult to debug without tooling.
The most reliable debugging approach is to map the stacking context tree rather than searching element-by-element. Start from the root and identify every element that creates a new context. For each context, list its z-index within the parent context. Then check whether the conflicting elements share a common ancestor context — if they do, compare their z-index values within that shared context. If they don't, the fix is at the ancestor level, not the element level.
This is exactly what the CSS Z-Index Visualizer does automatically. By parsing your CSS, it reconstructs the logical stacking context tree, assigns each element to its correct context, and flags cases where z-index values may produce unexpected layering.
Large codebases benefit from a formal z-index scale defined as CSS custom properties or design tokens. A common approach is to define named layers: --z-base: 1, --z-raised: 10, --z-dropdown: 100, --z-sticky: 200, --z-overlay: 300, --z-modal: 400, --z-toast: 500. This prevents the "z-index arms race" where developers keep incrementing values to win ordering battles.
The CSS @layer rule, introduced in modern browsers, provides a formal mechanism for controlling cascade order between stylesheets without relying on specificity or z-index hacks. While it primarily affects the cascade rather than painting order, combining cascade layers with intentional stacking context management produces the most maintainable results.
Using isolation: isolate on component root elements is a clean pattern for component-based architectures. By scoping z-index to a component boundary, you ensure that internal z-index values never accidentally conflict with external ones. This is the CSS equivalent of encapsulation for stacking order.
A frequently overlooked fact: z-index only applies to positioned elements. An element with position: static (the default) ignores z-index entirely. This means adding z-index: 100 to an element without also setting a non-static position value has no effect. The visualizer flags these cases as ineffective declarations, helping you identify dead CSS.
Elements with position: relative participate in stacking order even without an explicit z-index — they stack above static elements in document order. Understanding this default behavior is important when debugging layouts where a relatively positioned element appears above a fixed element despite no z-index being set.
Browser DevTools are excellent for inspecting computed styles on individual elements, but they don't provide a bird's-eye view of the entire stacking context structure. You have to navigate the DOM tree manually and mentally reconstruct the context hierarchy. This tool gives you that overview instantly from CSS alone — no browser required, no live page needed. It's ideal for code review, debugging during development, and learning how z-index behaves in complex scenarios.