CSS corner-left-shape Property

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Description

The corner-left-shape property controls the visual geometry applied to the left-side corners of a box, allowing designers to create notches, curves, beveled edges, or complex cutouts that affect how the element's left edges are painted. Rather than merely altering the radius of a corner, this property can define an independent, abstract shape for the left area so that top-left and bottom-left corners can share a single unified treatment or display a continuous molded profile. Because it targets a localized portion of the element's outline, it’s primarily used to give UI components distinctive silhouettes while keeping the rest of the box model unchanged.

Visually, corner-left-shape interacts with other rendering properties in predictable ways. It can clip backgrounds and backgrounds’ layers, so a textured or gradient fill will follow the left-shape contour rather than the rectangular frame; in that context it complements existing corner and masking tools such as border-radius and clip-path. Shadows and glows continue to be cast from the new outline, so effects defined with box-shadow will respect the adjusted silhouette, and image-based masks such as mask-image can be combined with the property to produce layered or partially transparent corner treatments.

On the layout and interaction side, using corner-left-shape changes hit-testing and the visual focus area only if the UA chooses to use the painted shape for pointer events or focus outlines; authors should be aware of how focus rings and keyboard navigation appear when an element’s outline no longer matches a simple rectangle. To preserve accessible focus visibility one may coordinate the property with outline behavior provided by outline. For floated or wrapped content, the altered left contour can also be used to influence text wrap when used in conjunction with shapes produced by shape-outside, producing tighter, more integrated layouts.

Finally, corner-left-shape is useful for responsive and animated UI patterns: the shape can morph across breakpoints to create subtle transitions between device sizes, and it can be animated or transitioned alongside transforms to produce engaging micro-interactions. When animating, be mindful of compositing and painting costs - combining the property with GPU-accelerated transforms such as transform can improve perceived performance, while frequent, large-scale shape changes may trigger more expensive repaints. Overall, the property offers a precise, designer-oriented control for tailoring an element’s left-side form without requiring entirely custom SVG assets.

Definition

Initial value: see individual properties
Applies to: see individual properties
Inherited: no
Computed value: see individual properties
Animatable: see individual properties
JavaScript syntax: object.style.cornerLeftShape

Syntax

corner-left-shape: <corner-shape>{1,2}

Values

The property accepts one or two <corner-shape-value> values. These define the style of the corner shape:

Keyword Values

round - The default value. Creates a standard rounded corner (equivalent to traditional border-radius).
scoop - Creates an inward-facing curve (concave), making the corner look "bitten" out.
bevel - Creates a flat, diagonal cut across the corner (chamfered look).
notch - Creates a rectangular step-like cutout at the corner.
square - Straight angle corner (no rounding)
squircle - Intermediate shape between round and square

Functional Value

superellipse(<number>) - Determines corner curvature using a superellipse curve.
- Larger positive numbers → closer to a square
- Values around 1 → default/round
- Negative values → inverted/concave shapes
- infinity and -infinity are allowed as extremes ([MDN Web Docs][1])

Global CSS Values

inherit
initial
revert
revert-layer
unset

Example

HTML

<div class="card corner-left-shape" style="--corner-left-shape: 56px; --corner-left-color: #ff6b6b;">

  <h2>Corner Left Shape</h2>

  <p>This card demonstrates a left-corner decorative shape controlled by a CSS custom property ("--corner-left-shape").</p>

</div>

CSS

*{
  box-sizing: border-box;
}

body{
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial;
  background: #f4f6f8;
  padding: 40px;
  display: flex;
  align-items: flex-start;
  justify-content: center;
  min-height: 100vh;
}

.card{
  position: relative;
  background: #ffffff;
  padding: 24px 24px 24px 32px;
  width: 320px;
  border-radius: 30px;
  box-shadow: 0 6px 18px rgba(20, 30, 45, 0.08);
  corner-left-shape: scoop;
  overflow: visible;
}

.card h2{
  margin: 0 0 8px 0;
  font-size: 18px;
  color: #102a43;
}

.card p{
  margin: 0;
  color: #334e68;
  line-height: 1.4;
  font-size: 14px;
}

Result

Editor

Browser Support

The following information will show you the current browser support for the CSS corner-left-shape property. Hover over a browser icon to see the version that first introduced support for this CSS property.