QR codes

Introduction

A QR code (Quick Response code) is a type of matrix barcode (or two-dimensional barcode) first designed in 1994 for the automotive industry in Japan. A barcode is a machine-readable optical label that contains information about the item to which it is attached. In practice, QR codes often contain data for a locator, identifier, or tracker that points to a website or application.

History

The QR code system was invented in 1994 by Masahiro Hara from the Japanese company Denso Wave. The initial purpose was to track vehicles during manufacturing; it was designed to allow high-speed component scanning. QR codes have since become one of the most popular types of two-dimensional barcodes, largely due to their fast readability and greater storage capacity compared to standard UPC barcodes.

Structure and Encoding

QR codes use four standardized encoding modes (numeric, alphanumeric, byte/binary, and kanji) to efficiently store data. The structure of a QR code includes several key components:

**Positioning Markers**: These are the large squares located in three corners of the QR code, which allow a scanner to recognize the code and determine its orientation.
**Alignment Markers**: These are smaller squares that help correct for distortion.
**Timing Pattern**: This alternating pattern of black and white modules helps the scanner determine the width of a single module.
**Version Information**: This indicates the version of the QR code (from 1 to 40), which determines the size and data capacity of the code.
**Format Information**: This stores information about the error correction level and the mask pattern of the QR code.
**Data and Error Correction Keys**: These are the actual data stored in the QR code, along with the error correction keys which allow the data to be recovered even if the code is partially damaged.

Error Correction

QR codes incorporate error correction to ensure that they can still be read even if they are partially damaged. The error correction capability is based on Reed-Solomon error correction. There are four levels of error correction:

**Level L**: 7% of data bytes can be restored.
**Level M**: 15% of data bytes can be restored.
**Level Q**: 25% of data bytes can be restored.
**Level H**: 30% of data bytes can be restored.

Applications

QR codes have a wide range of applications across various industries:

**Commercial Tracking**: Used in product tracking, item identification, time tracking, document management, and general marketing.
**Mobile Payments**: Used in mobile payment systems, such as Alipay and WeChat Pay.
**Marketing and Advertising**: Used to link directly to websites, promotions, and product information.
**Ticketing**: Used in electronic tickets for events, transportation, and more.
**Authentication**: Used in two-factor authentication systems to verify user identity.

Technical Specifications

QR codes are standardized under ISO/IEC 18004. The standard specifies the physical and logical characteristics of QR codes, including:

**Module Size**: The smallest unit of a QR code, which can vary in size depending on the application.
**Data Capacity**: Depending on the version and error correction level, QR codes can store up to 7,089 numeric characters, 4,296 alphanumeric characters, 2,953 bytes, or 1,817 kanji characters.
**Symbol Size**: QR codes can range from 21x21 modules (version 1) to 177x177 modules (version 40).

Security Concerns

While QR codes offer convenience, they also pose security risks. Malicious QR codes can direct users to phishing websites, download malware, or perform other harmful actions. It is crucial to verify the source of a QR code before scanning it.

Future Developments

The future of QR codes includes advancements in dynamic QR codes, which can be updated with new information without changing the code itself. Additionally, QR codes are being integrated with augmented reality (AR) and the Internet of Things (IoT) to provide more interactive and immersive experiences.