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Step-by-Step Diagnostic

Camera Block Detector

When a camera will not show video, the cause is usually one of four different things — a browser permission block, an OS-level privacy block, a driver or hardware conflict, or a genuine physical lens cover — and each needs different guidance. This runs an actual sequence of checks and tells you which one you are dealing with, rather than guessing from a single symptom.

Camera off

Checks

Diagnostic Steps

  • 1. Browser permission state:Checking…

—

  • 2. Camera stream test:Waiting

Click "Run Full Diagnostic" above to start.

  • 3. Frame content check:Waiting

Runs after the stream check succeeds.

Notes

What each result actually means

Browser permission deniedThe browser itself is blocking access. Fixable from the camera icon in your address bar or the browser's own privacy settings.
OS-level block (browser says granted, stream still fails)The most commonly missed cause — an operating-system privacy toggle sitting behind an already-granted browser permission. Check your OS's camera privacy settings directly.
No device foundHardware or driver issue — the browser cannot see any camera at all. Check cables, Device Manager, or whether the camera is disabled in the OS.
Could not start (in use)Almost always another application already holds the camera open. Close other video apps and tabs first.
Live but looks coveredPermission and stream both succeeded, but the image itself is near-uniformly black — consistent with a physical lens cover or privacy shutter left closed.

What this cannot check

No web page — this one included — can see other browser tabs, other applications, or background system processes. That is a deliberate security boundary, not a limitation of this specific tool. If you need to know exactly which application currently holds your camera, that information only exists at the operating-system level: Windows' camera privacy settings and Task Manager, or macOS's camera indicator and Activity Monitor, both show this directly.

Benchmark Reference

Real Browser Error Codes

Error nameDiagnosisFix
NotAllowedError (perm. granted)OS-level blockCheck OS camera privacy settings.
NotAllowedError (perm. not granted)Browser permission deniedClick the camera icon in your address bar.
NotFoundErrorNo device foundCheck cables, Device Manager, or OS-level disable.
NotReadableErrorCamera in use elsewhereClose other apps/tabs using the camera.
OverconstrainedErrorConstraint mismatch, not blockedNot actually inaccessible — request different settings.

These are the real, standard error names getUserMedia reports — this tool reads yours directly rather than guessing.

Step-by-Step

How to Run the Diagnostic

  1. Click "Run Diagnostic" — no setup needed.
  2. Respond to the permission prompt if one appears.
  3. Read the three-step readout: permission state, stream attempt result, and a frame-content check for physical obstruction.
  4. Follow the specific guidance shown for whichever error, if any, was actually detected.

Common Questions

Frequently Asked Questions

Can a website tell if another app is spying on my camera?
No, and any tool that claims to is not being straight with you. Browser security is specifically designed so a web page cannot see other tabs, other applications, or background processes — that isolation is a core protection, not a gap. This tool reports what a page genuinely can see: its own permission state and stream errors, plus a check of whether the live image looks physically obstructed.
My camera light is off but an app says it's in use — what's happening?
On the large majority of modern webcams, the indicator LED is wired directly to the camera's power rail specifically so software cannot disable it while hiding sensor activity. If the light is genuinely off, the sensor is almost certainly not capturing. Check your OS's own camera-usage indicator or Task Manager / Activity Monitor for which process actually has it open.
What does NotReadableError mean?
The camera was found but the operating system would not hand it over to the browser — almost always because another application already has it open. Close other video apps and browser tabs using the camera and try again.
How do I check which app is using my camera on Windows or Mac?
Windows 10 and 11 show a camera-in-use indicator in the system tray, and Settings → Privacy → Camera lists recent app access. macOS shows an orange/green indicator light plus, in recent versions, a dot in the menu bar you can click to see which app is using the camera or microphone.
Why does it say "permission granted" but the camera still won't start?
That specific contradiction — browser reports granted, stream still fails — is the clearest signature of an OS-level privacy block sitting behind an already-approved browser permission. It means something outside the browser, not the browser itself, is the actual blocker.