CSS Border Radius
CSS border-radius makes box corners from quarter ellipses using horizontal and vertical radii. It changes painting and clipping, but not the box's layout size, and it does not make a mathematical squircle.
Another example
A 40 px control uses a 12 px radius and is checked at 200% zoom. It keeps its target size, visible focus outline, correct clipping, shadows, and the same design token in every state. A 9999 px radius makes a pill, not a squircle.
Main parts
- 01horizontal radius
- 02vertical radius
- 03painting and clipping edge
Use it when
Use this term for CSS ellipse corners with clear radii while testing clipping, focus, shadows, and target size.
Do not use it when
Do not use border radius as a vague style word. Do not call every large radius a squircle. Clipping must not shrink the usable target.
Name used in code
border-radius: horizontal / vertical radii Before you ship
Check content order, shared design values, component consistency, contrast, zoom, and layout changes by screen size. Verify every theme, language, and state. If there is motion, offer an equal reduced-motion experience.
Outcome: Use or define CSS Border Radius to make the visual experience clear and easy to use. User context: A 40 px control uses a 12 px radius and is checked at 200% zoom. It keeps its target size, visible focus outline, correct clipping, shadows, and the same design token in every state. A 9999 px radius makes a pill, not a squircle. Design concept to apply: CSS Border Radius. Why it fits: Use this term for CSS ellipse corners with clear radii while testing clipping, focus, shadows, and target size. Do not use it when: Do not use border radius as a vague style word. Do not call every large radius a squircle. Clipping must not shrink the usable target. Design requirements: Set the content order, shared design values, and reusable components. Define how the layout changes by screen size and state. Keep useful design choices separate from decoration. Inclusion and resilience: Check contrast, zoom, languages, themes, and reduced motion when needed. Do not use color or effects as the only way to show meaning. Acceptance criteria: The design stays clear on phones and desktops, at zoom, in every theme, and in all supported languages. Interactive states stay clear and consistent. Evidence and limits (evidence boundary): A formal document may still be a draft, release candidate, or final version. Check its status and browser or platform support. Unknowns to confirm: Brand limits, amount of content, supported themes and languages, target devices, and design-system rules.
Check this request
Review the current use of CSS Border Radius. Definition: CSS border-radius makes box corners from quarter ellipses using horizontal and vertical radii. It changes painting and clipping, but not the box's layout size, and it does not make a mathematical squircle. Release checks: Check content order, shared design values, component consistency, contrast, zoom, and layout changes by screen size. Verify every theme, language, and state. If there is motion, offer an equal reduced-motion experience. Before changing code, report the evidence you found, gaps, severity, and the smallest safe fix.