Returns the geometric position, size, z-index, and viewport visibility for one or more DOM elements. Use to answer: where exactly on screen is this element? Is it visible? Is it off-screen?

Checks if one element physically overlaps another by computing the intersection of their bounding boxes. Use to answer: is this button hidden under a sticky header? Does the cookie banner block the CTA?

Validates a set of spatial layout rules — e.g. 'nav must be above hero', 'sidebar must be left of content'. Returns pass/fail per rule with a human-readable reason. Use to answer: does the page layout match the design specification?

Measures how element positions and sizes change across multiple viewport sizes. Use to answer: does the layout break on mobile? Which elements shift most when resizing?

Measures color contrast between a text element and its background using both WCAG 2.x and APCA (WCAG 3.0 draft) formulas simultaneously. Use to answer: does this text pass accessibility contrast requirements? Is it actually readable even if it technically passes the legacy formula?

Reveals the full CSS stacking context chain for an element — which ancestors create new stacking contexts and why. Use to answer: why is my z-index:9999 element still behind a modal? Does this element create its own stacking context?