What is a QR code and how do they work?

What is a QR code and how do they work?

Quick Response (QR) codes are two-dimensional barcodes that have become increasingly popular due to their ability to store a significant amount of data in a compact and easily scannable format. They can be found in various industries and applications, such as marketing, advertising, contactless payments, and information sharing. This comprehensive guide will discuss the basics of what a QR code is, how it works, and its many uses in today’s digital world.

  1. What is a QR Code?

A QR code is a two-dimensional matrix barcode that can store information both horizontally and vertically. This allows for more data to be stored within the code compared to traditional one-dimensional barcodes. Invented in 1994 by the Japanese company Denso Wave, QR codes were initially used for tracking automotive parts in manufacturing plants. Since then, their applications have expanded greatly, and they are now employed across numerous industries for various purposes.

QR codes consist of a pattern of black squares arranged on a white background, with three larger squares in the corners serving as position markers. The remaining squares contain the encoded data, which can be read and decoded by a compatible scanning device, such as a smartphone or a specialized QR code reader.

  1. How Do QR Codes Work?

QR codes function by encoding data in a machine-readable format, which can then be scanned and decoded by a compatible device. The process of encoding, scanning, and decoding a QR code can be broken down into several steps:

2.1. Data Encoding

The data to be stored in the QR code is first encoded using a specific algorithm. This algorithm converts the data into a series of binary values, which are then translated into a pattern of black and white squares. The encoded data is organized within the QR code according to a predetermined structure, which includes error correction codes to ensure the accuracy and reliability of the encoded information.

2.2. Scanning the QR Code

To read the information stored in a QR code, a compatible device, such as a smartphone, tablet, or specialized QR code reader, must be used. The device’s camera captures an image of the QR code, which is then processed by the device’s software to identify the position markers and determine the orientation of the code.

2.3. Data Decoding

Once the QR code has been scanned and its orientation determined, the device’s software decodes the data contained within the code’s pattern of black and white squares. The decoding process involves reversing the encoding algorithm, translating the binary values back into their original form.

The decoded data is then presented to the user, typically as a link, text, or other digital content.

  1. Types of QR Codes

There are several types of QR codes, each with its own characteristics and capabilities. The most common types include:

3.1. Numeric QR Codes

Numeric QR codes can store up to 7,089 numeric characters (0-9). These codes are ideal for encoding large amounts of numerical data, such as serial numbers, product codes, or phone numbers.

3.2. Alphanumeric QR Codes

Alphanumeric QR codes can store up to 4,296 alphanumeric characters, including numbers (0-9), uppercase letters (A-Z), and nine special characters (space, $, %, *, +, -, ., /, and :). These codes are suitable for encoding a mix of text and numbers, such as URLs, email addresses, or short messages.

3.3. Byte QR Codes

Byte QR codes can store up to 2,953 bytes of data, allowing for the encoding of any 8-bit binary data, such as images, audio files, or PDF documents. Byte QR codes offer greater flexibility

in terms of the types of data they can store, but their capacity is generally lower than that of numeric or alphanumeric QR codes.

3.4. Kanji QR Codes

Kanji QR codes are designed specifically for encoding Japanese characters and can store up to 1,817 Kanji characters. These codes use a unique encoding method optimized for the efficient storage of Kanji characters, making them well-suited for applications that require the encoding of Japanese text.

  1. QR Code Error Correction

One of the key features of QR codes is their built-in error correction capability. This allows QR codes to remain readable even if they are partially damaged or obscured. There are four levels of error correction available for QR codes, each providing a different degree of redundancy:

4.1. Level L (Low)

Level L error correction provides a 7% redundancy, meaning that up to 7% of the QR code’s data can be lost or damaged while still maintaining readability.

4.2. Level M (Medium)

Level M error correction offers a 15% redundancy, allowing for the recovery of up to 15% of the code’s data in case of damage or loss.

4.3. Level Q (Quartile)

Level Q error correction provides a 25% redundancy, ensuring that up to 25% of the QR code’s data can be recovered if damaged or lost.

4.4. Level H (High)

Level H error correction offers the highest degree of redundancy at 30%, allowing for the recovery of up to 30% of the QR code’s data in the event of damage or loss.

The choice of error correction level depends on the specific application and the potential risk of damage or obstruction to the QR code. Higher levels of error correction result in a larger QR code with a denser pattern of squares, which may require a higher resolution scanner for accurate reading.

  1. Applications of QR Codes

The versatility of QR codes has led to their widespread adoption across various industries and applications. Some of the most common uses for QR codes include:

5.1. Marketing and Advertising

QR codes can be used in marketing campaigns to provide users with quick access to promotional offers, product information, or company websites.

By scanning a QR code, users can instantly visit a specific web page or access digital content, eliminating the need to manually type out URLs or search for information.

5.2. Contactless Payments

QR codes are increasingly being used for contactless payment systems, allowing users to make secure transactions by scanning a QR code with their smartphones. This offers a convenient alternative to traditional payment methods, such as credit cards or cash.

5.3. Information Sharing

QR codes can be used to share a variety of information, including contact details, Wi-Fi network credentials, or event details. By scanning a QR code, users can quickly and easily access this information without the need for manual input.

5.4. Inventory Management and Tracking

QR codes can be used for tracking and managing inventory in warehouses or retail settings. By attaching a QR code to a product or package, businesses can easily scan and track the item throughout the supply chain, streamlining processes and improving efficiency.


QR codes are a powerful and versatile tool for encoding and sharing data across a wide range of applications and industries. Their ability to store significant amounts of information in a compact and easily scannable format, combined with their built-in error correction capabilities, make them an ideal choice for various tasks, from marketing and advertising to contactless payments and inventory management. With the continued growth of digital technology, it is likely that the applications and benefits of QR codes will continue to expand and evolve, further solidifying their importance in today’s interconnected world.

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