QR codes have become ubiquitous in our daily lives. You see them on products, advertisements, business cards, and more. QR codes allow us to quickly access digital information by scanning the code with a smartphone camera. However, like any technology, QR codes are not immune to errors. In this article, we will explore the main types of errors that can occur in QR codes and how they affect the code’s scanability and data recovery. Understanding these errors will help create better QR codes and know how to troubleshoot issues when they arise.
What is a QR code?
A QR code (short for Quick Response code) is a type of matrix barcode that can be read by a digital device like a smartphone camera. QR codes were invented in 1994 by the Japanese company Denso Wave to track inventory in vehicle manufacturing. Today, QR codes are used to encode all types of data, including website URLs, contact information, calendar events, and more.
QR codes work by converting data like numbers, letters, and symbols into a two-dimensional pattern of dark and light squares that can be scanned and interpreted by an imaging device. The black and white squares represent the binary code 0s and 1s that make up the encoded data. QR codes can encode up to 4,296 alphanumeric characters.
Types of errors in QR codes
There are several types of errors that can occur in QR codes that affect their scanability and ability to recover the encoded data accurately. The main errors include:
Physical damage
One of the most common ways QR codes can become unscannable is if the code printout becomes physically damaged in some way. This includes:
- Smudging or fading of the ink over time
- Rips, holes, or corner tears in the paper
- Crinkles, folds, or creases in the material
- Stains or other markings obscuring the code
Any physical damage of the printout that obscures or alters the position of the dark and light modules will affect the code’s scanability. Damaged areas interrupt the continuous binary pattern, making it unreadable by the scanning device.
Low print quality/resolution
QR codes must maintain a high print quality and resolution to be scannable. Low quality printing creates codes that are fuzzy or pixelated. This makes it hard for the scanner to accurately distinguish between the dark and light squares.
Common causes of low print quality include:
- Printer low on ink or needs maintenance
- Pixelated image before printing
- Low quality paper used
- Small code size
Always ensure codes are printed at a high DPI resolution and sharp image quality. The higher the print quality, the more scan-resilient the codes will be.
Insufficient data recovery capacity
QR codes have built-in redundancy to losslessly recover data even if parts of the code are damaged. However, there are limits to how much data recovery capacity a code has. The more data encoded, the less redundancy for recovery.
If a QR code is already maximized in data capacity and then experiences physical damage, there may not be enough redundancy left in the undamaged portion of the code to recover all the data. This will lead to incomplete or corrupted data extraction.
Structural errors
Errors can also occur if the QR code structure is programmed incorrectly. QR code generating software requires entering the right parameters and settings to produce a valid matrix pattern.
Structural errors include:
- Invalid data masks – Applying the wrong or multiple data masks
- Format information errors – Entering the wrong error correction level or other format settings
- Mismatched version and data capacity – Trying to encode more data than the version allows
Structural programming mistakes will generate flawed QR code designs that scanners will not be able to recognize or read properly.
Incorrect encodings
Encoding specifies how the input data gets converted into the binary 0s and 1s pattern. Using the wrong encoding scheme for the data type can lead to encoding errors.
- Encoding text characters using the wrong character set
- Failing to encode special data properly like URLs and contact information
- Not indicating when data inputs use multibyte encodings
Encodings optimize the QR code for compactness and efficient error recovery of different data formats. Picking the right encoding is key.
Effect of errors on QR code scanability
The main purpose of QR codes is to be scannable and accurately transfer encoded data to the end-user. Errors affect scanability in different ways:
Unscannable codes
Severe physical damage or very low print quality often makes QR codes completely unscannable. The camera simply cannot capture enough of the code or distinguish the module patterns. The code remains undetected or gets scanned as an invalid format.
Longer scan times
Minor to moderate issues like smudging, fading, or slightly low print resolution makes codes harder to scan. It takes the camera longer to recognize the code and brings it into focus for reading. Excessive scanning delays create a poor user experience.
Distance and angle scanning limitations
QR codes with quality issues can only be scanned properly within a very limited range of distance and angles. The scanner has to be held closer or at a straighter angle to the code compared to scanning high quality codes. This greatly restricts scanability flexibility.
Incorrect or corrupt data extraction
Data recovery failures lead to extracting incorrect or corrupt data that does not match the original inputted payload. This renders the QR code useless. It fails to transfer the intended information.
Improving QR code quality and scanability
Here are some tips to create high quality, scan-optimized QR codes:
Avoid physical damage
- Store and handle printouts carefully to prevent stains, tears, folds, etc.
- Cover codes with protective sleeves
- Laminate printed codes for durability
- Use scratch-resistant and waterproof materials
- Pick a sheltered spot away from direct sunlight to display outdoor signage codes
Print codes in high resolution
- Use printers and paper stock optimized for fine detail
- Enlarge code size if printing on low DPI medium
- Always use a print rather than digital screen display for codes
- Print a test code first to confirm quality before mass print production
Leave ample recovery capacity
- Avoid encoding overloaded data that maxes out code capacity
- Optimize encoding schemes for compact data representation
- Pick the right QR code version and error correction level to leave headroom for redundancy
Double check encodings
- Use recommended alphanumeric, binary, and Kanji encodings for input text strings
- Verify URL and contact encodings generate properly
- Specify when using multibyte UTF-8 characters
Validate code generation
- Use trusted QR code generator software
- Double check format settings and mask patterns
- Scan newly created codes to validate proper encoding
Following scanning best practices enhances QR code quality, reliability, and scanability.
Conclusion
QR codes provide a fast, convenient way to link the physical and digital world through instant data transfer. However, errors can render codes useless if they become unscannable or fail to recover data accurately. Physical damage, low print quality, insufficient error correction, structural mistakes, and encoding problems are common ways QR code quality becomes compromised. Severe issues make codes completely unreadable, while less serious problems lead to slower scanning, limited scanning range, and data corruption.
Careful QR code handling, high resolution printing, ample built-in redundancy, and double checking encodings enhances code resilience. When creating and displaying QR codes, vigilantly follow best practices to optimize quality and scanability. This ensures a seamless user experience and reliable data communication via QR codes.