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tailwindcss-squircles

A Tailwind CSS v4 plugin that progressively enhances rounded corners with squircles with the CSS corner-shape property.

Adding corner-shape: squircle on its own makes every corner noticeably sharper, because a squircle cuts less deeply into the corner than a circle with the same radius. This plugin multiplies the radius by the exact amount that evens it out (about 1.841 for a squircle).

Read my article on Squircles for a deeper look into the math and logic behind this plugin.

Install

pnpm add -D tailwindcss-squircles
# or: npm install -D tailwindcss-squircles

Requires Tailwind CSS v4.

@import "tailwindcss";
@plugin "tailwindcss-squircles";

What it does

Next to Tailwind's own definition, each rounded-* class gets two extra rules. One multiplies the radius inside @supports (corner-shape: squircle), the other sets the shape.

.rounded-xl {
  border-radius: var(--radius-xl);
}

@supports (corner-shape: squircle) {
  .rounded-xl {
    border-radius: calc(var(--radius-xl) * var(--corner-factor));
  }
}

.rounded-xl {
  corner-shape: var(--corner-shape, squircle);
}

• Theme values, arbitrary values, (--variables) and every side are covered, including the logical ones like rounded-es-*. Each side sets the matching corner-*-shape property.
• Compensated radii read var(--radius-*), so overriding a radius token still works.
• rounded-full and percentage radii like rounded-[50%] stay round. A pill must stay a pill.
• Radii with several values, like rounded-[10px_20px] or rounded-[10px_20px/5px], are multiplied part by part.
• Values with nothing to multiply, such as rounded-[inherit], keep Tailwind's own output.
• Side classes keep Tailwind's order, so rounded-lg rounded-t-full still ends with round top corners.

Changing the shape

Use the corner-* utilities next to a rounded-* class to change the shape of a single element. They change the curve and the compensation together.

<div class="corner-round rounded-lg"></div>
<div class="corner-bevel rounded-lg"></div>
<div class="corner-superellipse-1.5 rounded-lg"></div>

Class	Shape	Radius multiplier
corner-round	round	1
corner-squircle	squircle	~1.841
corner-bevel	bevel	~0.586
corner-scoop	scoop	1
corner-notch	notch	1
corner-square	square	1
corner-superellipse-<k>	superellipse(<k>)	exact for <k>

corner-superellipse-<k> accepts any number, negative ones included. scoop, notch and square have no corner depth to match, so the radius stays as written.

The shape and multiplier are set per element and don't inherit, so corner-round on a parent never leaks into its rounded children. In browsers without corner-shape support these classes do nothing.

How the multiplier works

For superellipse(k), the plugin multiplies the radius by

calc((1 - pow(2, -0.5)) / (1 - pow(2, -1 / pow(2, k))))

That is how far the circle's diagonal point sits from the corner, divided by the same distance on the curve. round is superellipse(1), so its multiplier is 1. A squircle is superellipse(2) (about 1.841) and a bevel is superellipse(0) (about 0.586).

Browser support

Browser	corner-shape
Chrome / Edge	Shipped in 139 (August 2025)
Safari	In Safari Technology Preview 251 (August 2026), not yet in a stable release

Check MDN for the current state.

License

MIT © Jesper Vos