Live geometry
Drag yellow handles · arrows = 1 unit · Shift = 5Shape it.
Radius anatomy
CSS can scale oversized corner radii at used-value time. The editor keeps your specified values intact while the Fit Audit shows the proportional scale the browser must apply.
Specified vs used radii
Overlap normalization
The CSS Borders algorithm computes one global factor
f. If any adjacent corner pair is too large for its side, every radius is multiplied by that same factor so the curves do not overlap.Experimental Corner Shape Lab
Progressive enhancement. Ordinary border-radius remains the fallback.
Checking browser support…
Progressive CSS
Fallback works everywhere that supports border-radius.
Writing mode mapper
Logical longhands
Useful for bidirectional and vertical layouts.
Radius scale
Design tokens
Includes pill/full semantic tokens.