This is a (Firefox) Web Extension, which makes it possible to generate a QR code from any website. In contrast to many other add-ons, which use Google Web APIs for that, this add-on works completely offline. This QR code generator puts your privacy first! Effectively, the add-on prevents any web connection for itself, so it does never contact the web. Thanks to the linked manifest.json you can also easily verify, that this claim is true. It works offline! Always.