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What Are QR Codes?
QR codes (Quick Response codes) are two-dimensional barcodes invented by Denso Wave in 1994. Unlike traditional barcodes that store data in one dimension, QR codes use a matrix of black and white squares to encode information both horizontally and vertically, allowing them to store significantly more data — up to 7,089 numeric characters or 4,296 alphanumeric characters.
QR codes include built-in error correction using Reed-Solomon algorithms, which means they can still be read even when partially damaged or obscured. This resilience, combined with their high data capacity and fast readability, has made QR codes ubiquitous in everything from product packaging to contactless payments.
How QR Code Reading Works
A QR code reader analyzes an image to locate and decode the QR code pattern. The process involves several steps, from detecting finder patterns to extracting the encoded data.
- Finder patterns — three large squares in the corners help the reader locate and orient the QR code regardless of rotation or angle
- Format and version info — encoded near the finder patterns, these tell the reader which error correction level and data encoding mode were used
- Data modules — the remaining black and white squares contain the actual encoded data, read in a specific zigzag pattern and decoded using the jsQR algorithm
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Scan a QR Code Now →Common Uses for QR Codes
QR codes have become essential in both consumer and enterprise applications due to their versatility and ease of use.
- URL sharing and marketing — QR codes on posters, business cards, and packaging link directly to websites, reducing the need to type long URLs
- Contactless payments — mobile payment systems like Apple Pay and Google Pay use QR codes for quick point-of-sale transactions
- Authentication and access — two-factor authentication apps scan QR codes to set up TOTP secrets, and event tickets use QR codes for entry verification
Frequently Asked Questions
How much data can a QR code hold?
A single QR code can store up to 7,089 numeric digits, 4,296 alphanumeric characters, or 2,953 bytes of binary data. The actual capacity depends on the error correction level chosen — higher error correction reduces data capacity but improves resilience to damage. Most practical QR codes store URLs or short text well within these limits.
Can damaged QR codes still be scanned?
Yes. QR codes use Reed-Solomon error correction at four levels: L (7%), M (15%), Q (25%), and H (30%). This means a QR code with level H correction can lose up to 30% of its data modules and still be decoded correctly. This is why QR codes work even when printed on curved surfaces or partially covered.
What is the difference between QR codes and traditional barcodes?
Traditional barcodes (like UPC or EAN) store data in one dimension using varying line widths, holding around 20-25 characters. QR codes store data in two dimensions using a grid of squares, holding thousands of characters. QR codes also include error correction and can be read from any angle, making them faster and more reliable to scan.