How QR Codes Work
A QR code encodes data in a grid pattern of black and white squares called "modules." When you scan the code, your phone's camera detects three large squares in the corners (finder patterns) to orient itself, then reads the data encoded in the remaining modules.
QR Code Capacity
- Numeric only: 7,089 characters (digits 0-9)
- Alphanumeric: 4,296 characters (A-Z, 0-9, spaces, $%*+-./:
- Binary/bytes: 2,953 bytes
- Practical limit: Keep URLs under 100 characters for reliable scanning
WiFi QR Code Format
WiFi QR codes use a specific text format that phones recognize automatically:
WIFI:S:YourNetworkName;T:WPA;P:YourPassword;;
Where S: is the SSID (network name), T: is the security type (WPA, WEP, or nopass), and P: is the password. This is what our WiFi tab generates automatically.
Real Example: Guest WiFi Setup
Say your guest network is named "CafeGuest" with password "welcome2024" using WPA2 security. The QR code encodes:
WIFI:S:CafeGuest;T:WPA;P:welcome2024;;
Print this QR code, frame it near the entrance, and guests connect instantly without asking for the password.
Print Size Guide
QR code size depends on scanning distance. Use this 10:1 rule:
| Use Case | Scanning Distance | Minimum QR Size |
|---|---|---|
| Business card | 15-20 cm (6-8 in) | 2 cm (0.8 in) |
| Product label | 30 cm (12 in) | 3 cm (1.2 in) |
| Table tent / Menu | 50 cm (20 in) | 5 cm (2 in) |
| Poster (wall) | 1-2 meters (3-6 ft) | 10-20 cm (4-8 in) |
| Billboard | 10+ meters | 1 meter+ |
Pro tip: Download SVG format for print. SVG is vector-based and scales to any size without pixelation. Use PNG only for web/digital display.
Error Correction Levels
QR codes have built-in redundancy. Even if part of the code is damaged or obscured (like a logo in the center), it can still scan. This generator uses "M" level (15% recovery), which balances size and reliability.
- L (7% recovery): Smallest code size, least damage tolerance
- M (15% recovery): Default. Good for most uses
- Q (25% recovery): Good for industrial environments
- H (30% recovery): Maximum recovery. Allows logo overlays
Static vs. Dynamic QR Codes
This generator creates static QR codes—the data is encoded directly in the image. Once generated, the destination can't change. This is actually an advantage:
- Works forever (no subscription needed)
- No tracking or analytics overhead
- Faster scanning (no server redirect)
- Works offline
Dynamic QR codes (from paid services) encode a short URL that redirects to your actual destination. Useful if you need to change the link later or track scans, but they stop working if the service shuts down.
Frequently Asked Questions
What is a QR code?
A QR (Quick Response) code is a two-dimensional barcode invented in 1994 by Denso Wave (a Toyota subsidiary) to track car parts. It stores data in a grid of black and white squares. Your phone's camera reads the pattern and extracts the encoded information—usually a URL, but also text, WiFi credentials, phone numbers, or contact cards.
Are the QR codes free to use?
Yes. Generate unlimited QR codes with no signup, watermarks, or hidden fees. Download as PNG (for screens) or SVG (for print), and use them commercially or personally. The QR code standard itself is open and patent-free since 1999.
Do QR codes expire?
Static QR codes never expire. The data is embedded in the image itself—it works as long as the image exists. The only way a QR code "expires" is if it links to a URL that goes offline, or if it's a dynamic QR code from a service that shuts down.
What size should my QR code be for printing?
Use the 10:1 rule: divide the scanning distance by 10. A poster viewed from 1 meter away needs at least a 10cm QR code. For business cards (scanned at ~20cm), 2cm minimum. Always test with an actual phone before printing a large batch.
Why won't my QR code scan?
Most common issues: (1) Poor contrast—light gray on white won't scan; use black on white. (2) Too small for the distance. (3) Blurry or low-resolution image. (4) Too much data making the pattern too dense. Try a URL shortener if your link is long, and download the larger size option.
How do I create a WiFi QR code for my business?
Click the WiFi tab above. Enter your network name exactly as it appears on devices (case-sensitive). Enter the password. Select WPA/WPA2 (most common). Generate and print. Laminate it and place near the entrance. Customers scan once and connect automatically—no more spelling out passwords.