Question 1

What is a QR Code?

Accepted Answer

A QR code (Quick Response code) is a two-dimensional matrix barcode invented by Denso Wave in 1994 for tracking automotive parts. It stores data in a grid of black and white modules arranged in a square pattern. Unlike traditional barcodes that are read in one direction, QR codes are read both horizontally and vertically — enabling much higher data density. Today QR codes are an ISO/IEC 18004 international standard used for mobile payments, marketing, authentication, and information sharing.

Question 2

Error correction levels

Accepted Answer

QR codes include built-in error correction using Reed-Solomon codes, allowing them to be read even when partially damaged, dirty, or obscured: L (7% recovery) — smallest QR code, best for clean digital screens. M (15%) — good default for most uses. Q (25%) — recommended for printed materials that may get worn. H (30%) — required if you plan to place a logo over part of the QR code. Higher correction levels increase the module density, making the code larger at the same data size.

Question 3

QR code use cases

Accepted Answer

Marketing & print — link flyers, posters, business cards, and packaging to websites, landing pages, or app downloads. Restaurant menus — replace physical menus with a scannable code linking to a digital menu, reducing printing costs and enabling real-time updates. Wi-Fi sharing — encode your network credentials so guests connect by scanning instead of typing the password. Payments — mobile payment systems (Venmo, PayPal, WeChat Pay) use QR codes for instant peer-to-peer and point-of-sale transactions. Event tickets — conferences, concerts, and boarding passes use QR codes for fast, contactless check-in. Authentication — two-factor authentication apps (Google Authenticator, Authy) use QR codes to share TOTP secrets during setup.

Question 4

QR code best practices

Accepted Answer

Minimum print size: A QR code should be at least 2 × 2 cm (0.8 × 0.8 in) for close-range scanning (business cards, product labels). For posters or signage scanned from a distance, the rule of thumb is 1/10th of the scanning distance — a code scanned from 1 meter away should be at least 10 cm wide. Contrast: Maintain a high contrast ratio between foreground and background — dark modules on a light background works best. Avoid low-contrast color combinations like light gray on white or yellow on white. Quiet zone: Leave a blank margin of at least 4 modules around the QR code — cropping this border can prevent scanners from detecting the code. Test before printing: Always test your QR code on at least 3 different devices (iOS, Android, and a tablet) before sending to print.

Question 5

QR code data capacity

Accepted Answer

A single QR code can store up to 7,089 numeric characters, 4,296 alphanumeric characters, or 2,953 bytes of binary data (at error correction level L). In practice, keep encoded URLs under 300 characters for reliable scanning across all devices and lighting conditions. Longer data increases the module density, making the code harder for cameras to read — especially at small print sizes or from a distance. Use a URL shortener for long links to keep the QR code simple and easy to scan.

Question 6

How to create a QR code

Accepted Answer

Type or paste your text, URL, or data into the input field. Choose an error correction level — M (15%) works for most situations; use H (30%) if you plan to overlay a logo. Optionally customize the foreground and background colors, keeping high contrast for reliable scanning. Click Generate to create the QR code, then click Download PNG to save the image. Test the code with your phone camera before using it in print or production.

QR Code Generator

What is a QR Code?

Error correction levels

QR code data capacity

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