The full English name of QR code is Quick Response code, which is a matrix QR code developed by the Japanese company Denso-Wave(a subsidiary of Toyota) in 1994.

QR codes are designed to be fast to read, and the name "Quick Response" reflects this feature. QR codes store more information than regular barcodes and do not need to be scanned in a straight line like regular barcodes. The QR code is square in shape and consists of black and white modules that contain parts such as a position detection pattern, a time pattern, format information, a data area, and an error correction code. These designs allow QR codes to be scanned from any angle and still be read correctly.

QR codes were registered as ISO/IEC standards in 2000 and have become an international way of encoding. It is widely used, commonly found in Japan, and has gradually become a popular two-dimensional space barcode worldwide.

A two-person development team

Denso Wave, a Japanese automotive company, is one of many automotive companies working on a standard UPC barcode system. Due to the limited storage capacity of barcodes, Denso Wave had to apply up to 10 barcodes on a single product to properly track and convey information. In addition, because barcodes need to be scanned from one direction, they run into production backup issues when scanners can not read barcodes on automotive parts of all shapes and sizes. The company struggled to meet deadlines simply because barcodes slowed down production.

In 1992, Masahiro Hara, who worked at Denso for the development of barcode scanners and optical character recognition (OCR) devices, received a request from a manufacturing plant to develop a barcode scanner that could read barcodes faster.

Initially, Masahiro Hara tried to respond to the needs of the field by improving the barcode scanner; However, he began to feel the limitations of the barcode system. In addition, at this very point, as the size of the product is getting smaller and smaller, there is a need to create codes that can be printed in a smaller area.

"We will develop a compact code that can store more information, including kanji and kana characters, while being able to read at a higher speed." It was decided to develop a new coding system.

"At that time, the QR codes developed by other companies focused on the inclusion of information," said Hara, who was in charge of the development of QR codes at the time.

Barcodes can only store information horizontally (in one dimension), in contrast to QR codes, which can store information in two dimensions vertically and horizontally. Hara invested in the development of a new QR code, thinking that in addition to being able to hold a large amount of information, "the developed code should also be easy to read". The R&D team consists of only two people. Hara initially tried to increase the capacity of the existing barcode, but was unsuccessful.

Later, Hara got the idea to write a new machine-readable code while playing the board game Go.

Hara began working on a new code, this time in the shape of not bars, but a square filled with a pixel-like pattern.

Barcodes are one-dimensional, and people have to scan them horizontally. The new code can be scanned both horizontally and vertically (hence two-dimensional). Being two-dimensional also meant that the new code could store more data than a barcode (more than 4,000 alphanumeric characters).

Soon, his team successfully iterated on the new machine-readable code. They named it the Quick Response Code, or QR Code, because it was dozens of times faster than a barcode. The new code worked even when it was 30% damaged.

But there was a flaw: the machine (camera) took time or could not read the QR code when it was distracted or scanned from an angle.

One day, on his way home, Hara noticed a building that stood out. The scene stuck in his mind and inspired him to try the QR code framework.

"There was a geometric pattern on the top of the building, which gave me the idea to create a QR code that used patterns," Hara said. Then they began looking for a unique symbol that would help machines recognize the QR code, even among other elements such as images and text.

During their research, the team discovered that machines could read the code faster when a certain pattern was attached to the three corners. However, it was not clear that they should use a pattern that was not found in any other code.

"Because this pattern appears least frequently in bills, etc.," Hara explained. In other words, if there is a similar pattern nearby, the reader will mistake it for a code, and to prevent this misreading, the positioning pattern must be a unique pattern. After comprehensive consideration, Hara and others decided to turn all the drawings and texts printed on flyers, magazines, cardboards, etc. into black and white and conduct a thorough investigation of their area ratios. As a result of investigating countless printed materials day and night, the R&D team finally found the "least common ratio" in printed materials, which is 1:1:3:1:1. In this way, the width ratio of the black and white parts of the positioning pattern was determined. The resulting structure is that the scanning line can be scanned from 360 degrees, and no matter which direction it is scanned from, once its unique ratio is scanned, the position of the code can be calculated.

QR codes have fixed patterns at three corners (called eyes) that form right angles from all directions. This design makes it easier and faster for machines to scan the QR code. The working principle of the QR code is to use binary operations, use 0 and 1 as codes, and use black and white squares to record information. The black square represents 1 and the white square represents 0. The black and white pattern is actually a string of codes. There are three large squares on the corners of the QR code, which mainly play a positioning role. Three points determine a surface, ensuring that users can successfully scan the code no matter where they are.

Two years later, the final product changed the rules of the game. QR codes solved all the previous shortcomings of barcodes (mainly data storage and scannability) and brought more benefits to customers.

For several consecutive years, QR codes have been certified by almost all major industry standards in Japan and around the world (including ISO). The European Patent Office even grandly awarded Hara the 2014 "European Invention Award". In the award speech, the representative of the European Patent Office stated that "the social value and scientific significance of QR codes are equally great."

How much data can be stored in a QR code depends on the type of data and the specific configuration of the QR code. The main types of data that can be encoded into a QR code include:

● Numeric: up to 7089 characters can be stored;

● Characters: Up to 4296 characters (including numbers, letters and some special characters) can be stored;

● Binary: up to 2953 bytes can be stored (can be used to encode binary data such as images or files);

● Kanji: Up to 1817 characters can be stored (used to encode Japanese kanji characters).

These values represent the maximum data capacity for each type under ideal conditions.

However, other factors can significantly affect the actual amount of data that can be stored and reliably decoded.

QR codes can store a wide range of information: text, website URLs, E-mail addresses, phone numbers, WiFi network credentials, calendar events, app download links, and more.

It can also be used for advanced functions, such as storing vCard information, location coordinate, and Bitcoin payment information.