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.

Map the four lengths without ambiguity

After an optional inset keyword, ShadowStack writes X offset, Y offset, blur radius and spread radius in that fixed order. Negative offsets move the shadow left or up; positive values move it right or down. Blur cannot be negative. Spread may be negative to contract the shadow shape before blur or positive to expand it. Every length is an integer pixel value, including zero, so copied code never depends on an omitted default. Change one field at a time and read the corresponding token before judging the visual result.

Keep colour and opacity auditable

The colour picker supplies a strict six-digit hexadecimal sRGB colour. Opacity remains a separate integer percentage so changing transparency never changes the chosen base colour. The copied declaration converts those inputs to modern rgb(R G B / A) syntax: zero and one are exact endpoints, while intermediate percentages become a decimal with at most two digits. This stable conversion makes repeated input produce byte-for-byte identical CSS. It does not perform colour management, blending prediction, contrast analysis or conversion to a design token.

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.