# videoRotationAngleForHorizonLevelPreview An angle the coordinator provides your app to apply to the preview layer so that it’s level relative to gravity. ``` var videoRotationAngleForHorizonLevelPreview: CGFloat { get } ``` ## Discussion Your app can get immediate rotation angle updates from the rotation coordinator with key-value observation (KVO) for this property. You can immediately update your app’s UI from its key-value observation code because the rotation coordinator notifies your app on the main queue. > Important: > Avoid unnecessary delays and visual artifacts by updating your app’s UI directly from an observer that monitors the property. Apps typically apply the property’s value to an [`AVCaptureConnection`](/documentation/AVFoundation/AVCaptureConnection) instance’s [`videoRotationAngle`](/documentation/AVFoundation/AVCaptureConnection/videoRotationAngle) property, such as displaying a camera preview with the correction for an [`AVCaptureVideoPreviewLayer`](/documentation/AVFoundation/AVCaptureVideoPreviewLayer) instance. Alternatively, if your app uses an [`AVCaptureVideoDataOutput`](/documentation/AVFoundation/AVCaptureVideoDataOutput) instance to display a custom camera preview, such as with effects, don’t rotate the video with [`AVCaptureConnection`](/documentation/AVFoundation/AVCaptureConnection). Instead, set the rotation in your instance’s property, such as with an [`AVSampleBufferDisplayLayer`](/documentation/AVFoundation/AVSampleBufferDisplayLayer) instance. This approach uses less energy than rotating each frame with the capture connection. > Note: > Your app needs to convert the ``doc://com.apple.avfoundation/documentation/AVFoundation/AVCaptureDevice/RotationCoordinator/videoRotationAngleForHorizonLevelPreview`` value from degrees to radians for an asset writer layer’s transform, which is a . --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)