[Radius lab]

border-radius
is not one number.

Four small ways the corner you asked for is not the corner you got.

01 / Percentages resolve per axis

width height radius

02 / The slash syntax

border-radius: 60px 20px 90px 10px / 20px 60px 10px 90px;

horizontal radii / vertical radii
tl tr br bl     / tl tr br bl

Every corner is an ellipse. Always was.

03 / Radii that don't fit get scaled down

top radius

04 / Outline follows radius (since 2021)

focus ring

outline used to be a rectangle around a rounded box.
Chrome 94 / Safari 16.4 / Firefox 88 fixed it.
Your 2019 focus-ring hacks can go now.

border-radiusis not one number.

border-radius
is not one number.