It's so simple, we almost don't need

documentation

because it's as easy as one, two, three.

step one:

quickresponse.co/de/[type]/data=[data]

Supported [type]'s: 'QR', 'C128' for EAN 128 subset B.

Determine if you need additional query params: [level = L], [size = 4]

Enjoy your generated [type] code!

Example:

quickresponse.co/de/qr?data=::&level=H&size=5

Result: