The CSS box-shadow property paints one or more shadows around an element without changing document layout. ShadowStack exposes only values that appear in the copied declaration, so the browser preview and source remain directly comparable. Each layer keeps its explicit paint order, inset state, four pixel lengths, hexadecimal colour and opacity.

Use one exact outer layer

Start from the default document: X is 0 px, Y is 12 px, blur is 28 px, spread is -8 px, colour is #0F172A and opacity is 28 percent. The result is box-shadow: 0px 12px 28px -8px rgb(15 23 42 / 0.28);. The negative spread contracts the source shape before the blur expands it, keeping the darkest region close to the card. Copy the declaration, test it on the actual card background, then adjust one number at a time if the card needs less separation or a different apparent direction.

Review the boundary, not only the blur

A soft shadow should not be the only feature separating an interactive card from its background. Inspect the card at normal and zoomed text sizes, keyboard focus and high-contrast preferences. If the boundary becomes unclear, add an explicit border or surface difference in the component CSS rather than making the shadow progressively darker. ShadowStack intentionally outputs only box-shadow, so those independent component decisions remain visible and reviewable in your own stylesheet.

Verify the CSS in its real component

ShadowStack renders the copied declaration with the current browser engine, but the preview is not a compatibility or accessibility certificate. Paste the property into the intended component and test every supported browser, responsive width, background and overflow container. A broad blur may be clipped by an ancestor and an inset shadow may cover content or focus indicators. Inspect keyboard focus at every state, measure text and control contrast with a dedicated tool, and retain a usable border or other non-shadow distinction when the interface depends on clear boundaries. The capsule stores no presets or history, so keep accepted CSS in your own source-controlled stylesheet before reloading.