Check camera access when the user starts the camera feature, request permission through the platform’s normal flow, and make sure the demo still works if access is refused or unavailable. Before presenting, rehearse first-time approval, denial, an existing grant, and a no-camera fallback. Browser demos also need the right HTTPS origin and, if embedded, permission from the host page.
What to check before you request access
Permission is not a permanent guarantee that a camera will be available. A user may change a setting, a temporary grant may expire, a browser policy may block capture, or another application may be using the device. Check the current state when the camera feature is about to be used, then handle the result of the actual capture attempt.
- Explain why the feature needs the camera at the point the user chooses to use it.
- Request access through the platform’s expected permission flow rather than prompting unexpectedly at launch.
- Keep the non-camera parts of the demo usable after denial or failure.
- Prepare a sample image or prerecorded clip that can demonstrate the central idea without live capture.
How to handle permissions on iOS
Before starting capture, check AVCaptureDevice.authorizationStatus(for: .video). Apple defines four states: notDetermined, authorized, denied, and restricted. See Apple’s authorization-status documentation and its camera access request documentation.
notDetermined: Request access when the user starts the camera-dependent action. Explain the purpose before the system prompt appears.authorized: Proceed with capture, while still handling device errors.denied: The user has already declined. Explain how to enable camera access in Settings and offer the non-camera route.restricted: The app is not permitted to use media capture devices. Do not imply that showing another prompt will fix it.
Add the NSCameraUsageDescription key to the app’s privacy configuration with a clear explanation of the camera’s purpose. Apple warns that a missing usage-description key can cause an exception when requesting access. The user can later change their choice in Settings, so check the current status again when the feature is used. If your access request uses a completion callback, update the interface on the main queue or MainActor.
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How to handle permissions on Android
Android uses a runtime permission flow. Follow the sequence in Android’s permission-request guidance: declare the required camera permission, give the user context, check the current grant, show rationale UI when shouldShowRequestPermissionRationale() indicates it, request permission, and handle the result.
- Declare the permission. Include the camera permission your app actually needs in its manifest.
- Explain the feature. Tie the explanation and request to the user’s camera action.
- Check and request. Check current permission state, show rationale UI when indicated, then launch the runtime request.
- Handle either result. On approval, continue to capture. On denial, leave the rest of the app usable and explain what the camera-dependent feature cannot do.
Starting with Android 11 (API level 30), users can grant camera access with “Only this time.” Android can also reset permissions for some unused apps. Do not assume a grant from an earlier run remains active. Android 12 (API level 31) adds privacy indicators when camera or microphone access is in use; account for these in the demo rather than treating them as an error. See Android’s documentation on requesting permissions.
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How to handle camera access in a browser
Request capture with navigator.mediaDevices.getUserMedia({ video: true, audio: false }). The page must be in a secure context, and the person must allow access. HTTPS is appropriate for a deployed demo; localhost is treated as secure for development. See MDN’s getUserMedia() reference.
Test the exact origin the judges will open, not just your development server. Confirm the browser is on the expected site and that camera access is not blocked in that site’s settings. The prompt may stay pending if the user ignores it, so show a waiting state and provide a way to cancel or continue without the camera.
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If the demo is embedded in an iframe
The top-level page must allow the embedded page to use the camera. Check the iframe’s allow attribute and the site’s Permissions-Policy header. Either can prevent access before the browser presents a permission prompt. See MDN’s camera Permissions-Policy reference.
Use browser permission state as a hint, not a guarantee
Where supported, the Permissions API can query the camera state as granted, denied, or prompt. That can help the interface explain what is likely to happen, but it does not replace attempting capture and handling its errors. A policy restriction may show up as denied without a user-facing prompt. See MDN’s Permissions API query reference.
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Show an actionable message for each capture error
Handle errors by name rather than displaying a generic “camera failed” message:
Quick Recap
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NotAllowedError: Access was denied, or the current context or policy does not allow it. Direct the user to the relevant site setting or explain that the embedding page must allow camera access.NotFoundError: No camera matches the request. Offer the sample media path.NotReadableError: The browser, operating system, or hardware could not provide the device even though permission was granted. Check for another application using or locking the camera, then retry.OverconstrainedError: The available camera cannot meet the requested constraints. Relax resolution or device requirements and retry.TypeError, or missingnavigator.mediaDevices: Check that the page is in a secure context and that the request constraints are valid.
Compare the three permission flows
| Environment | State check and request | Recovery concern | Demo-specific check |
|---|---|---|---|
| iOS | Check AVAuthorizationStatus; request access when appropriate. |
The user can change access in Settings; a missing usage-description key can break request setup. | Test a fresh install and a previously denied state. |
| Android | Check runtime permission, show rationale when indicated, request, and handle the result. | One-time grants and automatic resets mean earlier approval may no longer apply. | Test approval, denial, and behavior after a temporary grant ends. |
| Browser | Use getUserMedia(); a Permissions API query may supplement the check. |
Secure context, origin, iframe policy, device availability, and constraints can all affect capture. | Test the actual HTTPS presentation URL and embedded mode, if applicable. |
Run this preflight before presenting
- Install or open the demo with a fresh profile and test the first-time permission prompt.
- Test a previously denied permission, then verify the recovery instructions: Settings on iOS, and the relevant permission or site setting on Android or the browser.
- Test an existing grant and confirm the camera actually starts.
- On Android, test after an “Only this time” grant ends.
- Try the demo with no camera connected and with another application using or locking the camera.
- For a browser build, test the deployed HTTPS origin and the exact presentation route. If the page is embedded, verify its iframe allowance and Permissions-Policy configuration.
- Use only the camera constraints the demo needs; avoid brittle resolution or device requirements.
- Keep a local sample image or prerecorded clip ready, and rehearse switching to it without interrupting the presentation.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
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