`corner-block-start-shape` CSS property

Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The corner-block-start-shape CSS property specifies the shape of both the corners on a box's block-start edge, within their border-radius area.

For a full description of corner shape behavior and multiple examples, see the corner-shape shorthand property page.

Constituent properties

The corner-block-start-shape property is a shorthand for the following logical properties:

Syntax

css

/* Single keyword value set for both corners */
corner-block-start-shape: notch;
corner-block-start-shape: squircle;

/* Single superellipse() value set for both corners */
corner-block-start-shape: superellipse(2.7);
corner-block-start-shape: superellipse(-2.5);

/* Block-start/inline-start corner, block-start/inline-end corner */
corner-block-start-shape: notch squircle;
corner-block-start-shape: notch superellipse(-2.5);

/* Global values */
corner-block-start-shape: inherit;
corner-block-start-shape: initial;
corner-block-start-shape: revert;
corner-block-start-shape: revert-layer;
corner-block-start-shape: unset;

Values

The corner-block-start-shape property is specified using one or two <corner-shape-value> values:

If one value is used, it specifies the shape of both block-start corners.
If two values are used, the first one specifies the shape of the block-start/inline-start corner, and the second one specifies the shape of the block-start/inline-end corner.

Formal definition

Initial value	as each of the properties of the shorthand: `corner-start-start-shape`: `round` `corner-start-end-shape`: `round`
Applies to	all elements. It also applies to `::first-letter`.
Inherited	no
Computed value	as each of the properties of the shorthand: `corner-start-start-shape`: The corresponding superellipse() value. `corner-start-end-shape`: The corresponding superellipse() value.
Animation type	as each of the properties of the shorthand: `corner-start-start-shape`: Animates as per superellipse interpolation. `corner-start-end-shape`: Animates as per superellipse interpolation.

Formal syntax

corner-block-start-shape = 
  <'corner-top-left-shape'>{1,2}  

<corner-top-left-shape> = 
  <corner-shape-value>  

<corner-shape-value> = 
  round             |
  scoop             |
  bevel             |
  notch             |
  square            |
  squircle          |
  <superellipse()>  

<superellipse()> = 
  superellipse( <number>  |
  infinity                |
  -infinity )

Examples

You can find other related examples on the corner-shape reference page.

Basic `corner-block-start-shape` usage

HTML

The markup for this example contains a single <div> element.

html

<div></div>

CSS

We give the box some basic styles, which we've hidden for brevity. We also apply a box-shadow, a border-radius of 40px 60px, and a corner-block-start-shape of scoop notch.

body {
  font-family: "Helvetica", "Arial", sans-serif;
  width: 240px;
  margin: 20px auto;
}

div {
  width: 100%;
  height: 180px;
  display: flex;
  justify-content: center;
  align-items: center;
  background-color: goldenrod;
  background-image: linear-gradient(
    to bottom,
    rgb(255 255 255 / 0),
    rgb(255 255 255 / 0.5)
  );
}

css

div {
  box-shadow: 1px 1px 3px gray;
  border-radius: 40px 60px;
  corner-block-start-shape: scoop notch;
}

Result

The rendered result looks like this:

Specifications

CSS Borders and Box Decorations Module Level 4

corner-block-start-shape CSS property