# What is 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.

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

Published 2026-11-04.

`NSPanel` is a class in Apple's AppKit framework for a window that Apple describes as typically performing a function auxiliary to the main window. Palettes, inspectors and floating tool windows are panels.

## Why it matters

A normal window takes focus from the app you are using when it appears. For a panel you hover over to open, that would be disruptive: your typing would stop going where you were typing. A panel created with the `.nonactivatingPanel` style mask does not make its app the active one when you click it.

## How NotchStar uses it

The notch is an `NSPanel` with the `.borderless` and `.nonactivatingPanel` styles, placed above the [menu bar](https://www.notchstar.com/glossary/menu-bar/). The panel returns `false` from `canBecomeKey` by default, so it can take mouse events without taking keyboard focus. A second panel variant allows key status, and it becomes key only when a tool needs typing, such as Quick Notes or the teleprompter editor. SwiftUI draws the contents inside the panel through a hosting view.

## Why not pure SwiftUI

SwiftUI describes the views, but the window level, the style mask and the focus rules are AppKit features. A notch app therefore mixes the two: [SwiftUI](https://www.notchstar.com/glossary/swiftui/) for the views, [AppKit](https://www.notchstar.com/glossary/appkit/) for the window.

## Related

See [what is a notch app](https://www.notchstar.com/guides/what-is-a-notch-app/) for the user side, and [hover intent](https://www.notchstar.com/glossary/hover-intent/) for how opening is timed.

## 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 SwiftUI?](https://www.notchstar.com/glossary/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.
- [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 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.

## More in Developer terms.

- [What is SwiftUI?](https://www.notchstar.com/glossary/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.
- [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.