Scan
Point it at a mark.
Everything up to the moment you decide happens on this device. The camera never leaves your browser, and looking somebody up does not tell them, or us, that you did.
Looking
Fill the frame with the card, straight on. It will read a printed one, a screen, and either polarity.
Resolved
Scanning has not told them anything. A mark is an address, not permission to anything, so the only thing you can do next is ask, and they decide.
Read, but unknown