border-radius declaration.border-radius in CSS controls the roundness of element corners. When set to 50% on a square element it produces a circle; lower values give cards and buttons their distinctive rounded corners. This generator provides a live visual preview and outputs the cleanest possible CSS shorthand — avoiding the verbosity of writing all four corners manually.
The shorthand border-radius: 8px sets all four corners equally. border-radius: 8px 16px sets top-left+bottom-right to 8px and top-right+bottom-left to 16px. The full four-value form is top-left top-right bottom-right bottom-left. For elliptical corners, use the slash syntax: border-radius: 50px / 20px sets horizontal radii to 50px and vertical to 20px — creating oval corners. This generator handles all forms.
Set border-radius: 50% on an element where width equals height. The percentage is relative to the element's dimensions, so 50% makes each corner radius half the width/height — forming a circle.
The slash syntax (border-radius: 100px / 50px) sets different radii on the x and y axes — creating an oval/elliptical corner shape instead of a circular arc.
Any CSS length unit: px, em, rem, %, vw/vh. Percentages are relative to the element's width (for horizontal radius) and height (for vertical radius).
No. border-radius clips the visual rendering but the element's clickable area remains a rectangle. To clip the interactive area, use CSS clip-path or adjust the element shape at the DOM level.
See also the Box Shadow Generator and CSS Gradient Generator for complete CSS design tooling.