The corner-shape property controls the geometric treatment of an element’s corners beyond simple radii, letting authors define whether a corner is rounded, chamfered, notched, inset, bulging or follows a more complex custom curve. Rather than only affecting the visible curve of a border, it influences the element’s outline used for painting, hit-testing, and clipping—so it can change where background and foreground content appear near the corner, whether overflow is masked, and how the element responds to pointer events at its edges. Designers use it to produce distinct visual language for components (soft rounded cards, sharp angular controls, or decorative notches) while keeping the rest of the box model intact.

In practice corner-shape is commonly used alongside other corner- and clipping-related properties. For smoothing or rounding effects that were traditionally handled with border-radius, corner-shape provides finer control over multiple corner segments and asymmetric treatments. When you need to precisely clip the rendering region—so backgrounds, images or shadows are strictly confined—you often combine it with clip-path to create non-rectangular silhouettes or with shape-outside to influence float wrapping around a shaped box. Visual extras such as soft shadows should be considered together with box-shadow, since a corner’s geometry affects the shadow’s casting and visual continuity.

Beyond the visual result, corner-shape affects usability and performance trade-offs. Complex corner geometries may change an element’s hit area, so authors should ensure interactive targets remain large enough for accessibility and that focus outlines remain visible and legible. Animating corner geometry can produce engaging micro-interactions, but elaborate or frequently-updated custom curves may force repaints or compositing and thus require performance testing on target devices. It also has sensible fallback behavior: if a particular corner treatment isn’t supported by a user agent, it should degrade to a simpler geometric alternative so content remains usable and predictable.