---
title: Monitoring fit and field of view fidelity
framework: visionOS
role: sampleCode
role_heading: Sample Code
platforms: [visionOS 27.0+, xcode 27.0+]
path: visionos/monitoring-fit-and-field-of-view-fidelity
---

# Monitoring fit and field of view fidelity

Respond to changes in fit and field of view fidelity on Apple Vision Pro by using the Visual Fidelity API.

## Overview

Overview Some enterprise apps may need to verify an Apple Vision Pro wearer’s fit and field of view, often due to regulatory requirements. Use the Visual Fidelity API in ARKit to monitor how well Apple Vision Pro fits the wearer and whether they experience the required field of view. When fit accuracy or field of view coverage drifts out of range, the app can respond by coaching the wearer to adjust the fit or by making features that require accurate fit and field of view coverage unavailable. The sample shows how to monitor visual fidelity and visualize the required field of view for use in your own app: In a shared space, the person configures monitoring, and the app displays live updates on fit accuracy and field of view coverage. In an immersive space, the app outlines the required field of view as a series of spheres along each eye’s boundary. note: This sample requires an Apple Vision Pro. The Visual Fidelity API isn’t supported in the visionOS simulator. Configure the sample code project Replace Enterprise.license with your license file. The sample app requires a valid license file to monitor visual fidelity. Request the entitlement Visual fidelity monitoring is part of enterprise APIs for visionOS, a collection of APIs that unlock capabilities for enterprise customers. To use the Visual Fidelity API, you need to apply for the Visual Fidelity monitoring entitlement. For more information, including how to apply for this entitlement, see Building spatial experiences for business apps with enterprise APIs for visionOS. Start monitoring visual fidelity When you launch the sample, ContentView displays a Start Monitoring button, a Show Visualization button, and three controls bound to properties on AppModel: When the wearer taps Start Monitoring, ToggleMonitoringButton calls AppModel.startMonitoring(). The AppModel captures the current selections, creates a VisualFidelityProvider with them, and runs it on an ARKitSession: // AppModel.swift

let session = ARKitSession() let provider = VisualFidelityProvider(     fieldOfView: fieldOfView,     requestDeviceFitUpdates: requestDeviceFitUpdates,     presentCoachingAlerts: presentCoachingAlerts )

try await session.run([provider]) With the session running, ARKit delivers a stream of fidelity data to AppModel. Respond to fidelity updates When AppModel runs monitor(), it watches fidelity updates and stores the count, fit status, and field of view status that StatusView displays: // AppModel.swift

group.addTask { [weak self, provider] in     for await data in provider.fidelityDataUpdates {         await self?.apply(data)     } }

@MainActor private func apply(_ data: VisualFidelityData) {     updateCount += 1     deviceFitStatus = data.deviceFitStatus     isFieldOfViewValid = data.isFieldOfViewValid } Visualize the field of view When the wearer taps the Show Visualization button, the app opens an immersive space where ImmersiveView outlines each eye’s field of view using a series of spheres, blue for the left eye, red for the right. The button isn’t available when the wearer selects a custom polygon or device fit only, since ARKit only delivers FieldOfViewAnchor updates for presets. When AppModel runs monitor(), it watches anchor updates and stores each one in currentFieldOfViewAnchor: // AppModel.swift

group.addTask { [weak self, provider] in     for await update in provider.anchorUpdates {         await self?.setAnchor(update.anchor)     } }

@MainActor private func setAnchor(_ anchor: FieldOfViewAnchor) {     currentFieldOfViewAnchor = anchor } When currentFieldOfViewAnchor changes, ImmersiveView positions a pool of sphere entities to match the anchor’s per-eye polygon points: // ImmersiveView.swift

.onChange(of: appModel.currentFieldOfViewAnchor, initial: true) { _, anchor in     guard let anchor else {         leftContainer.children.removeAll()         rightContainer.children.removeAll()         return     }

let anchorSpace = anchor.coordinateSpace(correction: .rendered)     guard let transform = try? root.transform(from: anchorSpace) else { return }

sync(leftContainer, to: anchor.leftPolygonPoints, transform: transform, material: Self.leftEyeMaterial)     sync(rightContainer, to: anchor.rightPolygonPoints, transform: transform, material: Self.rightEyeMaterial) } Use the visualization to compare presets and confirm which one covers the regions your app depends on.

## See Also

### Enterprise APIs for visionOS

- [Accessing the main camera](visionos/accessing-the-main-camera.md)
- [Building spatial experiences for business apps with enterprise APIs for visionOS](visionos/building-spatial-experiences-for-business-apps-with-enterprise-apis.md)
- [Locating and decoding barcodes in 3D space](visionos/locating-and-decoding-barcodes-in-3d-space.md)