Fix guide · Webcam test
How to fix "NotReadableError: Could not start video source"
NotReadableError, also shown as "Could not start video source" or "Could not start audio source", means the browser found the device but could not open it. In almost every case another program is already using the camera or microphone, or a driver is stuck. Closing the other program fixes it most of the time.
Quick fix checklist
- 1Close video call apps such as Zoom, Teams, Skype, Discord and OBS, and any other browser tab that uses the camera or microphone.
- 2Quit and reopen the browser completely, including background windows.
- 3Unplug the device, wait five seconds and plug it into a different USB port.
- 4On Windows, in Sound settings turn off "Allow applications to take exclusive control of this device".
- 5Restart the computer if the device still will not open, then press Check again.
Why a free device can still be "busy"
Many cameras can serve only one program at a time. A meeting app left running in the tray, a browser tab with a call, a screen recorder or a virtual camera can hold the device even when you cannot see it. The system or a security tool may also lock it.
Hardware faults cause the same error. A loose USB cable, a failing port or a driver crash makes the device appear present but unreadable, and a restart or a new port usually clears it.
Check for a virtual camera or audio mixer
Tools that add a virtual camera or a virtual microphone can take control of the real device. Close them, or pick the real device inside the other app, then run the webcam test or microphone test again.
FAQ
Common questions
What does "Could not start video source" mean?
The browser found the camera but could not open it, most often because another app or tab is already using it.
Is my webcam broken if I see NotReadableError?
Usually not. Close other apps first. If it still fails on another computer too, then the camera or its cable may be faulty.
Why does it only happen in Chrome or only in Firefox?
A different browser may have grabbed the device, or one browser has a stale permission or extension. Close all browsers and try one at a time.
Can I use the camera in two apps at once?
Some modern cameras allow it, but most do not. A virtual camera app can share one camera between several programs.