Information capacity and versions of QR Code

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

On Double-Sided QR-Codes

Table 1 from Enhancing the Data Storage Capacity in QR Code Using Compression Algorithm and Achieving Security and Further Data Storage Capacity Improvement Using Multiplexing

How do QR codes encode information? - Quora

Figure 6 from QR-code generator

QR code

AI-driven artistic QR code generation went virus in China and overseas - PingWest

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

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

What is a QR Code?