QR codes (Quick Response codes) were invented by Denso Wave in 1994 to track automotive parts on assembly lines. Their ability to encode far more data than a traditional 1D barcode — up to 3,000 alphanumeric characters — made them ideal for URLs and text. The explosion of smartphone cameras with built-in QR readers in the 2010s, accelerated by contactless necessity during COVID-19, turned QR codes into a mainstream communication tool.
How QR Codes Work
A QR code is a 2D matrix of black and white squares (modules) arranged in a square grid. The three large square patterns in the corners (called finder patterns) allow scanners to detect the code's position, orientation, and scale. The data is encoded in binary and distributed across the remaining modules. Importantly, QR codes include Reed-Solomon error correction — a mathematical algorithm that allows the code to be read correctly even when up to 30% of the pattern is damaged, obscured, or covered by a logo.
Error Correction Levels
- Level L (Low): 7% of data can be restored — smallest file size, most fragile
- Level M (Medium): 15% of data can be restored — balanced choice for most uses
- Level Q (Quartile): 25% of data can be restored — good for printed materials
- Level H (High): 30% of data can be restored — required when placing a logo over the QR code
10 Practical Uses for QR Codes
- Restaurant menus — link to the online menu; no printing costs, always up to date
- Wi-Fi sharing — encode your network name and password so guests can connect without typing
- Business card links — encode your LinkedIn profile, portfolio, or contact vCard
- Event check-in — encode a ticket ID for fast scanning at the door
- Product packaging — link to a user manual, warranty registration, or video tutorial
- Print-to-digital campaigns — link a poster, flyer, or billboard to a landing page
- Retail price tags — link to product specifications, reviews, or online purchasing
- App store links — encode a direct link to download your app on iOS or Android
- Payment — encode a payment link (PayPal, Stripe, UPI) for in-person transactions
- Contact information — encode a vCard with name, phone, email for instant contact save
Minimum Print Size for QR Codes
A QR code must be large enough for a camera to resolve all the individual modules. The minimum recommended print size is 2 × 2 cm (about 0.8 × 0.8 inches) for codes that will be scanned from 20 cm distance (typical phone hold distance). For large-format printing (posters, billboards), increase size proportionally. Our generator outputs a 256 × 256 pixel PNG — upscale in a vector editor for large-format print to avoid pixelation.
Can I Put a Logo in the Middle of a QR Code?
Yes, if the QR code is generated with High (H) error correction level, which allows up to 30% of the pattern to be obscured while remaining scannable. Position the logo in the center (the area with least critical data), keep it to maximum 20–25% of the total QR code area, and always test scanning before printing or deploying.