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# routeChangeNotification

A notification the system posts when its audio route changes.

```
class let routeChangeNotification: NSNotification.Name
```

## Discussion

The <doc://com.apple.documentation/documentation/Foundation/NSNotification/userInfo> dictionary of this notification contains the [`AVAudioSessionRouteChangeReasonKey`](/documentation/AVFAudio/AVAudioSessionRouteChangeReasonKey) and [`AVAudioSessionRouteChangePreviousRouteKey`](/documentation/AVFAudio/AVAudioSessionRouteChangePreviousRouteKey) keys, which provide information about the route change.

See [Responding to audio route changes](/documentation/AVFAudio/responding-to-audio-route-changes) for more information on using this notification.

The system posts this notification on a secondary thread.

## Topics

### User Info Keys

[`AVAudioSessionRouteChangeReasonKey`](/documentation/AVFAudio/AVAudioSessionRouteChangeReasonKey)

A user info key that’s used to retrieve the route change reason.

[`AVAudioSessionRouteChangePreviousRouteKey`](/documentation/AVFAudio/AVAudioSessionRouteChangePreviousRouteKey)

A user info key that’s used to retrieve the previously active audio session route.

### User Info Values

[`AVAudioSession.RouteChangeReason`](/documentation/AVFAudio/AVAudioSession/RouteChangeReason)

Constants that indicate the reason for an audio route change.


---

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