• CSS stacking contexts create an imaginary z-axis, controlling element depth perception. • Position, z-index, opacity, transform, and filter each can trigger a new stacking context. • Elements with higher z-index don’t always appear on top; parent stacking contexts can override. • Nested stacking contexts stack independently, so child elements may be hidden behind siblings in parent stack. • To “unstack,” avoid auto z-index, use position: relative, and manage opacity/transform carefully. • Understanding stacking order is key for complex UI overlays, modals, and animated layers.

Article Summaries:

  • CSS stacking contexts determine the visual layering of elements on a webpage. Even a high z-index value can fail to bring an element to the front if it resides in a lower‑level stacking context created by properties such as position, opacity, transform, filter, or contain. Each context behaves like a “folder” that groups its children; once inside, elements cannot escape or reorder relative to elements in other contexts. The article explains how nested contexts work, why properties automatically generate new contexts, and offers practical strategies for “unstacking” elements to achieve the desired visual order.

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