QRBot от Kevin R

Generates a QR code for the URL of the current page in the browser. Handy for sharing links between devices, among other things.

This doesn't require any network connectivity at all to run; the QR code is generated completely locally.

Note that while generating a QR code doesn't require any network access, scanning a QR code on another device could access the network, depending on how it's implemented. That isn't under the control of this add-on.