Quick check: Run the related device test and keep it open while trying these steps.
Start with the preview
Open the webcam test and look at a stationary object at your normal sitting distance. Check the displayed resolution, but do not assume a higher number guarantees a sharp image. A blurry picture at every resolution usually calls for a lens, focus or lighting check. Make sure you selected the intended camera if your laptop and external webcam are both connected.
Put light in front of you
Face a window or lamp rather than placing the bright light behind your head. A backlit scene can cause your face to look dark as the camera tries to expose for the background. A soft, steady light is easier for the camera to handle than a small glaring bulb. Move the light and compare the preview before buying equipment.
Check lens and focus
Clean the lens gently with a suitable microfiber cloth and verify a privacy cover is fully open. Some webcams have a manual focus ring; turn it slowly while watching the preview. Autofocus models may hunt if the room is very dark or an object sits close to the lens. Move nearby objects away and give the camera a moment to settle.
Separate preview from call quality
If this local preview looks good but your video call looks poor, the calling service may be reducing quality because of bandwidth or app settings. If both look poor, troubleshoot the camera and lighting first. This test shows what the browser receives on your device and does not measure the image another person receives across a network.
After each change, test the device again. Change one setting at a time so you can identify what helped.
Further reference: Official device or browser documentation ↗