Put light in front of you, not behind you
The easiest improvement is to face a window or lamp so the front of your hand is evenly lit. A bright window behind you makes your hand dark relative to the background and can hide finger separation. You do not need studio lighting; consistency is more useful than brightness.
Avoid rapidly changing light sources such as a television behind the camera. Stable light gives the tracker a more consistent view from one gesture to the next.
Frame the full hand
Keep your palm facing the lens and leave space around the fingertips. If a fingertip is cropped, finger count becomes less dependable. Sitting roughly an arm’s length from the webcam is a useful starting point: close enough for detail, far enough that the whole hand stays in frame.
Place the camera at approximately chest or face height when possible. A severe upward or downward angle can make the palm and fingers overlap visually.
Simplify the background and remove conflicts
A plain background reduces visual distraction. You do not need a blank wall, but avoid holding your hand against a moving screen, another person, or a similarly colored patterned object when troubleshooting.
Close video-call apps and other tabs that may own the camera. Browsers generally cannot share a webcam cleanly between multiple active applications.
Confirm the browser permission
When the browser asks for permission, choose Allow for the intended camera. If you clicked Block earlier, use the lock icon beside the address bar to update site settings, then reload the page. The browser is the authority for camera permission; the web page cannot bypass that choice.
Gesture Synth requests video for hand tracking and does not request microphone audio. You can revoke the camera permission in browser settings whenever you want.