Camera and microphone permissions
Also called getUserMedia · site permissions
Browsers only let a page use your camera or microphone after you allow it. The operating system can also block access for every browser at once. A blocked permission looks exactly like a broken device.
The webcam and microphone tests process everything on your device. Nothing is uploaded.
In practice
Camera and microphone permissions are layered. The browser asks for each site and remembers the answer. The operating system also controls which apps may use the camera and microphone at all. A no at either level makes the device look broken even though nothing is wrong with the hardware.
How to check
If the microphone or webcam test can’t see your device, look for a blocked camera or microphone icon in the browser’s address bar and allow it. Then check the operating system privacy settings for camera and microphone and make sure your browser is allowed.