Run MicAndCam first to prove the browser can see and hear your devices, then match the same devices inside Zoom.
Start the mic test, speak normally, and record a short clip. Then start the webcam test, turn on the grid if you want help framing yourself, and check lighting and sharpness. Finally, play the speaker Left, Right, and Both tones at low volume.
If these checks work, your hardware and operating-system permissions are probably fine. A remaining Zoom issue is likely the selected microphone, selected camera, speaker output, or Zoom's own audio processing.
Open Zoom settings and check Audio and Video. Pick the same headset, USB microphone, built-in camera, or external webcam you just tested. If Zoom offers separate speaker and microphone tests, run both after matching the device names.
If the webcam is black in Zoom but works in MicAndCam, close virtual camera apps and make sure Zoom is not set to a virtual camera source with no active scene.
Stop the mic and camera tests on MicAndCam before joining. That releases the devices for Zoom and avoids one app holding the camera while another tries to open it.
For Bluetooth headsets, test the speaker and mic separately. Some headsets switch profiles when the microphone is active, so Zoom may sound different from a normal music test.
Zoom may be using a different input, camera, or output. Pick the same devices in Zoom settings and close apps that may already be using the camera.
It can be when the tool runs locally. MicAndCam analyzes microphone levels, camera preview, snapshots, and recordings in your browser and does not upload media. You can verify this with the live counter or your browser's Network panel.