Let's start by saying that QR corresponds to the initials of Quick Response. QR codes are a type of matrix barcode (or two-dimensional barcode). They were invented in 1994 by the Japanese engineer Masahiro Hara, from the Japanese company Denso Wave, a subsidiary of Denso Corporation. This company is dedicated to the production of automatic identification equipment (barcode readers and related products), industrial robots and programmable logic controllers.
Originally, the purpose of QR codes was to keep track of auto parts made by Denso, then part of the Toyota Group, to replace multiple barcodes on each box, each of which had to be scanned separately.
QR codes became popular outside of the automotive industry, due to their fast readability and higher storage capacity compared to standard UPC (Universal Product Code) barcodes.
A QR code consists of black squares arranged in a grid on a white background, including some fiducial markers, which can be read by an imaging device such as a camera and processed using Reed-Solomon error correction (an error-correcting code based on in blocks where the encoder processes a block of data symbols, to which it adds redundancy to produce a block of encoded symbols), until the image can be properly interpreted. The required data is then extracted from the patterns that are present in the horizontal and vertical components of the image.
Currently, QR codes are highly customizable. For example, in Zebra QR you can change the color of the boxes or the background in the code editor. They are also used in a much broader context, including commercial tracking applications and convenience-oriented applications targeted at mobile phone users (referred to as mobile tagging).
QR codes can be used to display text to the user, to open a web page on the user's device, to add a vCard contact to the user's device, to open a Uniform Resource Identifier (URI), to connect to a wireless network or to compose an email or text message. There are plenty of QR code generators available as software or as online tools that are either free like Zebra QR or require a paid subscription. The QR code has become one of the most widely used two-dimensional code types globally.