---
title: NSExtensionPrincipalClass
framework: bundleresources
role: symbol
role_heading: Property List Key
path: bundleresources/information-property-list/nsextension/nsextensionprincipalclass
---

# NSExtensionPrincipalClass

The custom class that implements an app extension’s primary view or functionality.

## Discussion

Discussion This key is mutually exclusive with NSExtensionMainStoryboard. Typically, Xcode sets the value of this key when creating an App Extension target in your project. If you change the name of the specified class, remember to update the value of this key. important: If the app extension’s Info.plist file contains both keys, the system won’t load the extension.

## See Also

### Appearance and Presentation

- [NSExtensionActionWantsFullScreenPresentation](bundleresources/information-property-list/nsextension/nsextensionactionwantsfullscreenpresentation.md)
- [NSExtensionMainStoryboard](bundleresources/information-property-list/nsextension/nsextensionmainstoryboard.md)
- [NSExtensionOverridesHostUIAppearance](bundleresources/information-property-list/nsextension/nsextensionoverrideshostuiappearance.md)
- [NSExtensionPointIdentifier](bundleresources/information-property-list/nsextension/nsextensionpointidentifier.md)