QR 码生成器 — 免费在线创建 QR 码

How QR Codes Work

A QR code is composed of black and white squares called modules arranged in a square grid on a white background. The code contains several key components:

• Finder patterns — Three large squares in the corners that help scanners detect and orient the QR code regardless of rotation
• Alignment patterns — Smaller squares that help correct for perspective distortion when scanning at an angle
• Timing patterns — Alternating black and white modules between finder patterns that define the grid coordinates
• Format information — Encodes the error correction level and mask pattern used
• Data and error correction — The actual encoded data along with Reed-Solomon error correction codewords

QR codes support four encoding modes: numeric (digits 0-9), alphanumeric (digits, uppercase letters, and symbols), byte (arbitrary binary data including UTF-8), and kanji (Japanese characters). The encoder automatically selects the most efficient mode for the input data.

Error Correction Levels

QR codes use Reed-Solomon error correction to remain readable even when partially damaged or obscured. There are four levels of error correction, each offering a trade-off between data capacity and resilience:

QR Code Data Types

• URL — The most common use. Encoding a full URL (e.g., https://example.com) allows scanners to open the link directly in a web browser
• WiFi — Uses the WIFI:T:WPA;S:NetworkName;P:Password;; format. When scanned, most smartphones will prompt to join the WiFi network automatically
• Email (mailto:) — Encodes an email address with optional subject and body using the mailto: URI scheme. Opens the default email client on the scanning device
• Phone (tel:) — Encodes a phone number using the tel: URI scheme. Scanning initiates a phone call
• SMS — Encodes a phone number and optional message using the sms: URI scheme. Opens the messaging app with a pre-filled recipient and message
• Plain Text — Any arbitrary text content. Useful for encoding messages, serial numbers, product information, or any other textual data

QR Code Size and Scanning Distance

QR codes come in 40 versions (sizes), ranging from 21×21 modules (version 1) to 177×177 modules (version 40). The library automatically selects the smallest version that fits your data. When printing or displaying QR codes, consider these guidelines:

• Minimum size — Each module should be at least 0.33mm (about 1/76 inch) for reliable scanning
• Scanning distance — As a rule of thumb, the scanning distance is approximately 10 times the QR code width. A 3cm QR code can be scanned from about 30cm away
• Quiet zone — Maintain a white border (margin) of at least 4 modules around the QR code for reliable detection
• Contrast — Ensure strong contrast between the dark and light modules. Black on white provides the best readability
• Print resolution — For print, export at 300 DPI or higher. SVG format is ideal for print as it scales without quality loss

Best Practices for QR Codes

• Keep the encoded data as short as possible — use URL shorteners for long URLs to produce smaller, easier-to-scan QR codes
• Test your QR code with multiple scanning apps and devices before distributing it
• Use error correction level M or higher for printed materials that may get creased, stained, or worn
• Avoid inverting colors (white on black) as some older scanners may not read inverted QR codes
• Do not distort the aspect ratio — QR codes must remain perfectly square
• If adding a logo overlay, use error correction level H and keep the logo small (no more than 10-15% of the QR code area)
• For dynamic content, consider using a URL that redirects to the target — this lets you update the destination without reprinting the QR code
• Always provide a text alternative (URL, phone number) alongside the QR code for accessibility