# What is SwiftUI?

> SwiftUI is Apple's framework for declaring an app's user interface in Swift code. Learn what it does, how it meets AppKit and how NotchStar uses both.

Canonical: https://www.notchstar.com/glossary/swiftui/
Last updated: 2026-11-04

Published 2026-11-04.

SwiftUI is Apple's framework for declaring an app's user interface and behaviour across its platforms. You describe what the screen should show for a given state, and SwiftUI draws it and keeps it up to date. Apple lists it as available on macOS from 10.15.

## Why it matters

SwiftUI means less code for each screen and the same views across Apple platforms. For a Mac app, it is usually combined with [AppKit](https://www.notchstar.com/glossary/appkit/), the older framework for windows and system integration, because some jobs still need AppKit.

## How NotchStar uses it

NotchStar is a native Mac app in Swift using SwiftUI and AppKit. Views such as the tool tabs are SwiftUI. The notch window is an AppKit [NSPanel](https://www.notchstar.com/glossary/nspanel/) that hosts them.

One practical limit came up while recording demo clips. An AppKit control, `ProgressView`, did not redraw in offscreen captures: the time text updated but the bar did not. The fix was a small SwiftUI `ThinBar` and `Spinner`, in `ToolStyle.swift`. It is a reminder that a control which looks the same on screen can behave differently when you draw it somewhere unusual.

## Related

Read [what is a notch app](https://www.notchstar.com/guides/what-is-a-notch-app/) for the product side. Live gauges such as the [System tool](https://www.notchstar.com/features/system-stats/) are plain SwiftUI views over data sampled once a second.

## Keep reading.

- [What is AppKit?](https://www.notchstar.com/glossary/appkit/): AppKit is Apple's older framework for building Mac apps with windows, menus and events. Learn what it covers and why SwiftUI apps still use it.
- [What is NSPanel?](https://www.notchstar.com/glossary/nspanel/): NSPanel is the AppKit window class for auxiliary windows such as palettes and utility panels. Learn why a notch app uses a non activating one.
- [What is a notch app? A plain English guide](https://www.notchstar.com/guides/what-is-a-notch-app/): A notch app turns the dead space around the MacBook notch into a tiny control center. Here is how they work, what they do and what to watch for.
- [CPU, memory, disk, battery and network](https://www.notchstar.com/features/system-stats/): Live CPU, memory, disk, battery and network speed gauges in your Mac notch. Sampling only runs while the tab is open, so it stays light.

## More in Developer terms.

- [What is NSPanel?](https://www.notchstar.com/glossary/nspanel/): NSPanel is the AppKit window class for auxiliary windows such as palettes and utility panels. Learn why a notch app uses a non activating one.
- [What is AppKit?](https://www.notchstar.com/glossary/appkit/): AppKit is Apple's older framework for building Mac apps with windows, menus and events. Learn what it covers and why SwiftUI apps still use it.
- [What is NSPasteboard?](https://www.notchstar.com/glossary/nspasteboard/): NSPasteboard is the AppKit object that moves data to and from the Mac clipboard. Learn how apps read it and why clipboard managers poll change count.
- [What is MediaRemote on macOS?](https://www.notchstar.com/glossary/mediaremote/): MediaRemote is a private Apple framework that reports what is playing on a Mac. Learn why it is restricted since macOS 15.4 and how notch apps work around it.
- [What is hover intent?](https://www.notchstar.com/glossary/hover-intent/): Hover intent is a short delay before a hover opens something, so passing the pointer by does not trigger it. Learn how NotchStar tunes it at the notch.
- [What does open source mean?](https://www.notchstar.com/glossary/open-source/): Open source software publishes its source code under a license that lets others read and change it. Learn the definition and how it differs from closed source.