---
title: "Why do Apple's corners look softer?"
code: JZ-008
series: Craft
published: 2026-11
updated: 2026-11-06
author: Joost van der Zwan
canonical: https://softwarebehavior.com/notes/jz-008
skill: studio-jz-apple-corners
license: CC BY 4.0
---

# Why do Apple's corners look softer?

Field Note JZ-008 · Craft · Apple corners

**67%** liked curved objects, against 51% for sharp-angled versions

## The guess
A bigger radius makes a corner softer.

## What the research found
A standard rounded corner is a straight edge plus a quarter circle, so the bend starts all at once at one point. A continuous corner (often called a squircle) eases into the bend: curvature builds up gradually and is tightest in the middle of the corner. Apple's SwiftUI offers both, as "quarter-circle" and "continuous curvature" corners. In a related study, people who saw objects for 84 ms liked curved versions more than sharp-angled ones (67% against 51%).

## Why
The eye picks up the point where a straight edge suddenly becomes a curve; a gradual change in curvature has no such point. This mechanism is a design claim, not a tested finding.

## What to do
- Use continuous corners where the platform offers them (SwiftUI RoundedRectangle with style .continuous; corner smoothing in Figma, the iOS preset).
- Keep nested corners concentric: inner radius equals outer radius minus the padding.
- Use the same corner style across a product, so cards, buttons and sheets match.

## What not to do
- Claim that continuous corners are proven to be preferred; they have not been tested head to head.
- Fake continuous corners by turning up the radius; a bigger quarter circle still starts abruptly.

## Limits
- No study found that compares continuous corners with ordinary rounded corners directly.
- Bar and Neta compared curved objects with sharp-angled versions, not two kinds of rounded corner. 14 participants, grayscale images, 84 ms exposure.
- Strong associations (a snake, a chocolate bar) can override the curvature preference.

## Example
- Before: Cards with 24 px quarter-circle corners and buttons with 8 px corners, each set by eye.
- After: Continuous corners on cards and buttons, with nested elements using concentric radii.

## Sources
- Bar, M. & Neta, M. (2006). Humans prefer curved visual objects. Psychological Science, 17(8), 645–648. https://doi.org/10.1111/j.1467-9280.2006.01759.x
- Apple Developer Documentation. RoundedCornerStyle (SwiftUI): circular and continuous. developer.apple.com/documentation/swiftui/roundedcornerstyle

## Use with your AI
This note is also a skill: `studio-jz-apple-corners` (version 1.0.0, in review). All skills: https://softwarebehavior.com/field-kit

Software Behavior Field Notes by Joost van der Zwan · Studio JZ · CC BY 4.0 · softwarebehavior.com