title: Confirming Source Is From QR Code Scan
body: <p>I have this project where I need to know if a visitor legitimately arrived from a QR code. Document.referrer value from a QR code shows blank. I have looked at some answers suggesting to put parameter in the query string (e.g. <code>?source=qr</code>), but anyone could easily add the parameter into the URL and my code would believe it is from a QR code (e.g. <code>www.project.com/check.page?source=qr</code>) . I have thought of adding codes to make sure it is from a mobile phone / tablet as secondary way to authenticate but many browsers have add-ons to fool websites.</p>
  
  <p>Any suggestions would be greatly appreciated. </p>
  
  <p>Thanks in advance.</p>