What is a QR Code? Can you create an unlimited number of them?

QR Code, or Quick Response Code, is a technology developed by Denso Wave in Japan in 1994. Originally designed for tracking automotive parts in vehicle manufacturing, QR codes have now become a ubiquitous technology worldwide, applied across various domains including payments, marketing, tourism, and inventory management. This article explains the limitations in creating QR codes, their structure, and applications in daily life.

1. Capacity and Limitations of QR Codes

Basic Structure of QR Codes

A QR code is a two-dimensional code consisting of black and white square dots arranged in a grid pattern. The key components include:

1. Finder Patterns: Square patterns at three corners of the QR code that help scanners locate and orient the QR code
2. Alignment Patterns: Patterns that help correct image distortion, especially in larger QR codes
3. Timing Patterns: Rows and columns of alternating black and white dots that help define the coordinates of each module
4. Version Information: Data indicating the version of the QR code
5. Format Information: Information about error correction level and mask pattern
6. Data and Error Correction Codewords: Areas storing the actual data and error correction codes

Capacity of Different QR Code Versions

There are 40 versions of QR codes, each with different sizes and capacities:

1. Version 1: 21x21 modules
2. Version 2: 25x25 modules
3. Version 3: 29x29 modules
4. To...
5. Version 40: 177x177 modules

Data capacity also depends on the type of data stored and the error correction level. There are 4 error correction levels:

1. L (Low): Can recover approximately 7% of data when the QR code is damaged
2. M (Medium): Can recover approximately 15% of data
3. Q (Quartile): Can recover approximately 25% of data
4. H (High): Can recover approximately 30% of data

Maximum capacity of a Version 40 QR code with error correction level L:

1. Numeric: 7,089 characters
2. Alphanumeric: 4,296 characters
3. Binary (8-bit): 2,953 bytes
4. Kanji/Japanese: 1,817 characters

Are QR Codes Limited in Number?

From a theoretical perspective, the number of different QR codes is finite, as the maximum capacity of a Version 40 QR code is 2,953 bytes. However, in practical terms, this number is so immense that it is effectively unlimited.

For binary (8-bit) encoding in Version 40, one could create 2^(2,953*8) different QR codes, or approximately 2^23,624 different patterns. This is an astronomical number far beyond what could ever be used in the real world.

To understand the magnitude of this number, the observable universe contains approximately 10^80 or 2^266 atoms, which is significantly less than the number of possible QR codes.

Therefore, it can be said that in practical terms, the number of QR codes that can be created exceeds what humanity could ever use, making them effectively unlimited.

2. Technology Behind QR Codes

Encoding and Decoding Process

The process of creating a QR code involves several key steps:

1. Data Analysis: The system analyzes what type of data is being encoded (numeric, alphanumeric, binary, or Kanji)
2. Data Encoding: Converting the data into binary code according to standards
3. Error Correction Addition: Using Reed-Solomon algorithm to create error correction codes
4. Data Arrangement: Arranging data and error correction codes into the modules of the QR code
5. Masking: Applying various mask patterns to prevent patterns that might lead to reading errors
6. Adding Format and Version Information: Adding information about the encoding format and version of the QR code

Decoding a QR code works by:

1. Image Capture: A camera captures an image of the QR code
2. Image Analysis: The system identifies the position and orientation of the QR code from the finder patterns
3. Module Reading: Reading the value of each module as black or white
4. Decoding: Converting back to the original data using relevant algorithms
5. Error Correction: Using error correction codes to recover potentially damaged data

Innovation and Development of QR Codes

Since its invention in 1994, QR code technology has continuously evolved:

1. Micro QR Code: A smaller version that uses less space than regular QR codes, suitable for applications with limited space
2. iQR Code: Supports both square and rectangular shapes, can store more data than regular QR codes in the same space
3. Frame QR: Designed with a center area for logos or images, enhancing aesthetics and brand recognition
4. Dynamic QR Code: QR codes that can change destination content without changing the QR code itself
5. Secure QR Code: Incorporating additional security features such as data encryption, authentication, and anti-counterfeiting protection

Today, QR codes are also being developed to be more aesthetically pleasing with QR Code Aesthetic Design techniques that remain readable despite decoration or color additions.

3. Applications of QR Codes in Daily Life

Payment and Financial Applications

QR codes have become an essential tool in digital payment systems:

1. Mobile Banking: Banks use QR codes to facilitate money transfers and payments through mobile applications
2. Digital Wallets: Such as PromptPay, Alipay, WeChat Pay use QR codes for transactions
3. Cashless Payments: Merchants display QR codes for customers to scan for payment, or have customers generate QR codes for the merchant to scan
4. Account Linking: Registration or linking financial accounts with various applications
5. Electronic Receipts: Issuing receipts in QR code format to reduce paper usage

Marketing and Advertising Applications

QR codes are effective tools for connecting the physical world with the digital world:

1. Website Access: Customers can scan QR codes to quickly access websites or landing pages
2. Coupons and Discounts: Distributing coupons or discounts in QR code format usable both in-store and online
3. Engagement Stimulation: Using QR codes for voting, surveys, or participation in activities
4. Increasing Social Media Followers: Customers can scan to follow brands on various social media platforms
5. Contact Information Sharing: Sharing contact information or digital business cards via QR codes

Education and Learning Applications

QR codes play an important role in enhancing learning efficiency:

1. Supplementary Learning Materials: Books or learning materials with QR codes linking to demonstration videos, audio, or additional information
2. Assessment: Students scan QR codes to take tests or submit assignments
3. Virtual Tours: Educational institutions use QR codes to present virtual tours of locations
4. Access to Library Resources: QR codes on books or shelves for accessing reviews, additional information, or related digital resources
5. Digital Learning Documents: Sharing teaching and learning documents in digital format via QR codes

Tourism and Travel Applications

QR codes help make tourism experiences more convenient and informative:

1. Boarding Passes/Tickets: Airlines, trains, and other transportation services use QR codes as electronic tickets
2. Tourist Attraction Information: Tourists can scan to view information, history, or stories about tourist attractions
3. Restaurant Menus: Restaurants use QR codes instead of paper menus, especially during the COVID-19 pandemic
4. Maps and Routes: QR codes on signs or brochures leading to online maps or navigation applications
5. Check-in Registration: Hotels use QR codes for check-in registration and access to hotel information

Conclusion

This article explains the limitations and capabilities of high-capacity QR Codes across different versions, as well as their use in everyday life such as payment, marketing, education, and tourism. QR Codes can store a variety of data types and can be used in many contexts. However, the number of QR Codes that can be created is virtually unlimited in practice. For those who want to create QR Codes for free with no expiration or wish to shorten links, a service is available at URLkub for convenience and quick usage.