🎯 Z-Index Stacking Visualiser
Runs entirely in your browser - no data sent to server
Output appears here...
📊 Key Data Points
Stacking contexts
The actual source of most z-index bugs — not the z-index values themselves
z-index: 9999 is a code smell
Indicates stacking context confusion — low values (0-10) are sufficient for most UIs
Modals need body parent
Place modals as direct children of body to escape intermediate stacking contexts
Z-Index Manager — CSS Stacking Context Visualizer -- Complete USA Guide 2026
Z-index bugs are caused by stacking contexts — not by the z-index values themselves. An element with z-index: 9999 inside a parent with opacity: 0.99 is isolated in a new stacking context and cannot appear above elements outside that context, regardless of its z-index value.
This visualizer shows which elements create stacking contexts and how z-index values compare within each. Runs in your browser.
**Long-tail searches answered here:** z-index manager online free, css z-index stacking context tool browser, manage css layer stacking order visualizer free.
For CSS debugging, pair with CSS Specificity and CSS Filter Generator.
🔬 How This Calculator Works
Visualizes z-index stacking order for a list of elements. Shows which elements create new stacking contexts (position + z-index, opacity < 1, transform, filter, isolation: isolate) and which z-index values conflict. Helps understand why an element with z-index: 9999 can be hidden behind an element with z-index: 1 when they are in different stacking contexts.
✅ What You Can Calculate
Stacking context visualization
Shows which elements create new stacking contexts and isolates them from each other. Makes the reason for unexpected stacking order immediately visible.
Z-index conflict detection
Highlights z-index values that conflict within the same stacking context. Elements in different stacking contexts are not comparable.
Stacking context triggers
Lists all CSS properties that create stacking contexts: position + z-index, opacity < 1, transform, filter, isolation: isolate, will-change.
Layer ordering diagram
Visual diagram showing the stacking order of all elements, grouped by their stacking context.
🎯 Real Scenarios & Use Cases
Debugging modal behind content
Your modal has z-index: 9999 but is hidden behind an element with z-index: 1. Visualize here to find the stacking context that is isolating the modal.
CSS animation z-index issues
CSS animations that use transform or opacity create stacking contexts. Visualize here to understand why an animated element z-index behavior changes during animation.
Frosted glass layer ordering
A frosted glass panel with backdrop-filter creates a stacking context. Visualize the layer ordering here to ensure the panel appears above the correct elements.
Navigation dropdown ordering
Navigation dropdowns need to appear above page content. Visualize the stacking contexts in your page to ensure the dropdown z-index will work as expected.
💡 Pro Tips for Accurate Results
Stacking contexts are the source of most z-index bugs. An element with z-index: 9999 inside a parent with opacity: 0.99 is isolated in a new stacking context — it cannot appear above elements outside that context regardless of its z-index value.
Properties that create stacking contexts. position + z-index (not auto), opacity < 1, transform (any value), filter (any value), isolation: isolate, will-change (several properties).
Use small z-index values. A scale of 0-10 is sufficient for most UIs. z-index: 9999 is a code smell indicating stacking context confusion.
Modals need a dedicated stacking context. Place modals as direct children of body to escape any intermediate stacking contexts.
🔗 Use These Together
🏁 Bottom Line
Z-index bugs are caused by stacking contexts — not by the z-index values themselves. This visualizer shows which elements create stacking contexts and how z-index values compare within each context. For CSS debugging: CSS Specificity and CSS Filter Generator.
Why is my z-index not working even with a very high value?
Z-index only works on positioned elements (position: relative, absolute, fixed, or sticky). An element with position: static ignores z-index entirely — add position: relative to enable it. The other reason z-index fails: stacking contexts. An element cannot stack above the parent element's stacking context boundary. If a parent has opacity less than 1, transform, filter, will-change, or isolation: isolate, it creates a new stacking context. Its children are stacked relative to each other within that context, not globally. A z-index: 9999 child of an opacity: 0.99 parent may still appear behind an element outside that parent with z-index: 1.
What creates a new CSS stacking context?
A stacking context is created by: position: fixed or sticky (always). position: relative or absolute with z-index not auto. opacity less than 1 (even 0.99 creates a context). transform (any value including transform: translateZ(0)). filter (any value). will-change (transform, opacity, or most properties). isolation: isolate (explicitly creates a context). mix-blend-mode (other than normal). contain: layout or paint. The CSS properties backdrop-filter, perspective, and clip-path also create stacking contexts. This is why applying transform: translateZ(0) as a performance hack can unexpectedly break z-index layering.
What is the recommended approach for managing z-index in a design system?
Define a z-index scale as CSS custom properties: --z-base: 0; --z-raised: 10; --z-dropdown: 100; --z-sticky: 200; --z-overlay: 300; --z-modal: 400; --z-toast: 500; --z-tooltip: 600. Use these named values in components instead of arbitrary numbers (z-index: 9999 is a smell — it means someone lost track of the scale). Document which layer each component belongs to. Tailwind CSS uses z-0, z-10, z-20, z-30, z-40, z-50 as defaults. The key insight: leave large gaps between values to allow insertion without renumbering the entire scale.
How do I debug which stacking context an element belongs to?
Browser DevTools: in Chrome, the Elements panel shows computed styles. Look for any of the stacking context triggers in the parent hierarchy: transform, opacity, filter. Firefox has a 3D view (toggle with the cube icon) that visualizes stacking order. Programmatically: use window.getComputedStyle(element) to check all parent elements for context-creating properties. A useful debugging technique: temporarily set outline: 2px solid red on the problematic element and its stacking context parents to visualize their boundaries.
Why does position: fixed not work as expected inside certain containers?
position: fixed positions an element relative to the viewport — but this breaks inside any parent that creates a stacking context via transform, filter, or will-change. A fixed sidebar inside a container with transform: translateX(0) (a common off-canvas menu technique) is positioned relative to the transformed container, not the viewport. The fix: move fixed elements outside the transformed container, up to the document root level. This is a frequent source of modal and dropdown positioning bugs in web applications.
What is the difference between z-index and elevation in design systems?
Z-index is a CSS implementation detail — an integer controlling stacking order. Elevation is a design concept from Material Design representing how far above the surface a component appears, using shadows to communicate height. In Material Design: elevation 0dp = flat surface (no shadow), elevation 8dp = card hover state, elevation 24dp = dialog. Each elevation level maps to a specific box-shadow value. The CSS z-index is usually correlated with elevation but is a separate concern. A tooltip (high z-index to appear above everything) may have low elevation (minimal shadow) while a raised card has high elevation but lower z-index than the tooltip.
What other CSS debugging tools are on this site?
The CSS Specificity Calculator explains why certain CSS rules override others — a related debugging challenge. The Box Shadow Generator builds the elevation shadows used alongside z-index. The Flexbox Generator and Grid Generator create layouts without needing z-index for most positioning. The Color Contrast Checker verifies readability for elements at different z-index layers. The CSS Filter Generator explains how filter creates stacking contexts. All are in the Dev Tools section.