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# collectionJoinBehavior

The behavior that specifies how a new scene joins a scene collection.

```
var collectionJoinBehavior: UISceneCollectionJoinBehavior { get set }
```

## Discussion

A scene collection is a group of scenes that display together. In apps built with Mac Catalyst, you use this behavior to add windows to an <doc://com.apple.documentation/documentation/AppKit/NSWindowTabGroup>.

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