Inspired by @rafa’s https://docktor.site, I created Squircle - a free Mac app that adds the correct corner radius, padding, and shadow to square app icons following Apple's design guidelines. Just drop the square icon in and out you get a single png or an appiconset for Xcode.

https://apps.apple.com/us/app/squircle-resize-app-icons/id6499279814

Docktor, for Mac

Preview app icons in the Dock

Docktor, for Mac
While creating this app, I discovered that macOS app icons aren’t just smooth rounded rectangles or continuous rounded rectangles, as Sketch and SwiftUI call them, but rather a cubic Bézier curve with 52 points. I solved this problem by inspecting the SVG representation of this curve to get the coordinates for a SwiftUI shape.
@mikakruschel OMG yes! This is so useful, thanks for making this 🫶
@mikakruschel @rafa thank you! I can't tell you how stupidly annoying it is for me to make a macOS icon for one of my apps, no clue why Apple didn't build this into Xcode like they did for iOS
@mikakruschel @rafa Oh! I looked for exactly this a few days ago! Nice! 🎉

@mikakruschel I've been using some Pixelmator templates I found on GitHub to create macOS icons, but your app is so much better - thank you! 🙌🏼

https://github.com/Zabriskije/macOS-Icons/tree/main/Pixelmator

macOS-Icons/Pixelmator at main · Zabriskije/macOS-Icons

Replacement app and document icons for macOS. Contribute to Zabriskije/macOS-Icons development by creating an account on GitHub.

GitHub
@mikakruschel @matthewcassinelli @rafa I think something is wrong with my App Store account. I’ve never had one of my reviews appear. Did you see my review for Squircle?
@com No, I haven't received any ratings or reviews for Squircle yet. Not sure what could be going on, but I appreciate your attempt nonetheless.
@mikakruschel Grrrr. I'm not sure what's going on. When I try to click “Manage Reviews and Ratings” in the account settings of App Store I get this. Booo Apple.
@mikakruschel this is exactly what I’ve been looking for! 🤩
@mikakruschel @rafa thanks for this app! my eagle eyes notice that the shadow is not quite the same as standard macOS icons. any plans to adjust it to match? cheers!