What are QR codes?

Quick Response or "QR" codes are standardized machine readable two-dimensional barcodes that can encode... just about any data, but they are most often used to store web addresses or other URIs for quick sharing.

Support for scanning QR codes has grown to be nearly ubiquitous in smart phone cameras and their use was popularized and normalized in the global COVID-19 pandemic.

Dynamic QR codes

Dynamic QR codes are nothing magic. They are entirely standard QR codes that contain a stable URL. However, instead of loading a web page the stable URL instructs the browser loading it to go to a different page.

While the stable URL in the QR code does not change, the target URL can be updated at any time so that future scans go to a new location.

This also allows for tracking scans of the QR code, because people loading the stable URL can be logged and processed.

Example:

Ee generates a Dynamic QR code on scancity.net to point to their website: https://durbin.ee/
scancity.net returns Ee a QR code with the URL https://scancity.net/qr/69420
When someone scans the QR code, they are sent to https://scancity.net/qr/69420, which logs the scan and forwards the user to https://durbin.ee/
Later, Ee logs into scancity.net and updates their QR code to point to https://eedurbin.com/
Immediately after, any new scans of the QR code will still load https://scancity.net/qr/69420 which will log the scan and forward to https://eedurbin.com/