How the preview works
The page asks for a user-facing video track at an ideal 1280×720. What you actually get depends on the driver. The readout is videoWidth × videoHeight from the element, not the constraint you asked for — that is the honest number.
Mirror is a CSS transform. It does not flip the underlying frames. Useful when you are lining up a ring light; useless as a claim about the sensor.
On pagehide and Stop, every track is ended. That releases the LED on most laptops. If the LED stays on, another tab or app still holds the device.
FAQ
Is my webcam video uploaded?
No. There is no capture pipeline to a server. The stream lives in this document.
Black screen?
Follow webcam black screen.