---
title: primary
framework: appkit
role: symbol
role_heading: Type Property
path: appkit/nswindow/collectionbehavior-swift.struct/primary
---

# primary

The behavior marking this window as primary for both Stage Manager and full screen.

## Declaration

```swift
static var primary: NSWindow.CollectionBehavior { get }
```

## Discussion

Discussion Marking a window collection behavior as primary means it becomes primary for both Stage Manager and full screen display modes. To set a different behavior in full screen while keeping Stage Manager primary, set a more specific behavior just for full screen mode (see fullScreenAuxiliary). Use this collection behavior for document or viewer windows. note: This property is mutually exclusive. Set only one of primary, auxiliary, or canJoinAllApplications on a window handled by Stage Manager at a time.

## See Also

### Stage Manager and full screen

- [auxiliary](appkit/nswindow/collectionbehavior-swift.struct/auxiliary.md)
- [canJoinAllApplications](appkit/nswindow/collectionbehavior-swift.struct/canjoinallapplications.md)