Information capacity and versions of QR Code

There are 40 versions of the QR Code. Details of these are explained here.

iQR Code

Data Matrix Codes vs. QR Codes – What is the Difference?

Barcodes vs. QR Codes: Which Is Best for Your Business?

How to Make a QR Code in 5 Easy Steps

The Introduction to Quick Response (QR) Code, by JIN

QR codes

To increase data capacity of QR code using multiplexing with color coding: An example of embedding speech signal in QR code

What is a QR code?, Basics of 2D codes, Barcode Information & Tips

Color Can Triple QR Code Capacity