CSS corner-top-left-shape Property

If this site has been useful, we’d love your support! Consider buying us a coffee to keep things going strong!

Description

The corner-top-left-shape property controls the geometric form of an element’s top-left corner independent of the other corners, allowing authors to create discrete visual treatments such as rounded, beveled, notched, concave, or ornamental corner profiles. Rather than treating the corner as a simple radius or a square cut, it expresses the final outline that the element’s border, background, and hit area should follow at that corner, so that the visual edge, painting, and interaction boundary can be tuned precisely for design needs.

This property is intended to compose with other corner and clipping mechanisms: for simple circular rounding it can complement or override border-top-left-radius, while for complex polygonal or freeform cuts it can be combined with or replaced by a clip-path to achieve non-rectangular silhouettes. When applied, the corner geometry also affects how shadows are rendered; box shadows will typically follow the modified outline so that effects applied via box-shadow remain visually consistent with the new corner shape. Similarly, the way backgrounds are painted near the edge can interact with background-clip, so designers should consider how background fills and borders intersect with the custom corner profile.

From a practical standpoint, corner-top-left-shape is useful for card components, bespoke UI chrome, and decorative details where per-corner differentiation improves aesthetics or brand alignment. It can be animated to morph corners as part of interactive states (hover, focus, or transition-driven motion) to produce subtle, high-quality effects. Because complex corner geometries may require additional paint or compositing work, developers should be mindful of potential performance costs on low-powered devices and test for smoothness when animating or applying large numbers of shaped elements.

Finally, when relying on this property in a responsive layout or when accessibility and interaction are important, remember that altering the visual outline can change the element’s hit test region and how content flows near that corner. If a particular corner treatment might obscure or clip critical content, pair the corner shape with appropriate clipping, padding, or hit-testing strategies so the visual design does not impede usability or leave interactive targets inconsistent with their appearance.

Definition

Initial value: round
Applies to: all elements where border-radius can apply
Inherited: no
Computed value: n/a
Animatable: yes
JavaScript syntax: object.style.cornerTopLeftShape

Syntax

corner-top-left-shape: <corner-shape>

Values

The property accepts one <corner-shape-value> value. 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='page'>

  <div class='card'>

    <h2>Top-left shaped corner</h2>

    <p>Using the experimental corner-top-left-shape property with a mask fallback for wider support.</p>

  </div>

</div>

CSS

/* Page layout */
body {
  font-family: Inter, system-ui, -apple-system, 'Segoe UI', Roboto, 'Helvetica Neue', Arial;
  background: #f4f7fb;
  margin: 0;
  min-height: 100vh;
  display: grid;
  place-items: center;
  padding: 40px;
}

.page {
  display: grid;
  gap: 16px;
}

/* Card with a shaped top-left corner */
.card {
  width: 360px;
  padding: 20px 24px;
  color: #fff;
  background: linear-gradient(135deg, #4b7bff 0%, #6fe7ff 100%);
  box-shadow: 0 8px 24px rgba(23, 43, 77, 0.12);
  border-radius: 25px;
  position: relative;
  corner-top-left-shape: scoop;
  /* Keep text inside safe area */
  overflow: hidden;
}

.card h2 {
  margin: 0 0 8px 0;
  font-size: 1.25rem;
}

.card p {
  margin: 0;
  opacity: 0.95;
  line-height: 1.4;
}

/* Small responsive tweak */
@media (max-width: 420px) {
  .card { width: 320px; padding: 18px; }
}

Result

Editor

Browser Support

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