QR Code Complete Guide: Create, Scan, and Use QR Codes

March 29, 2026 · 10 min read

How QR Codes Work

QR (Quick Response) codes were invented by Denso Wave in 1994 for tracking automotive parts. They encode data in a 2D matrix of black and white modules (squares). Unlike barcodes which store data in one dimension, QR codes use both horizontal and vertical axes, allowing much more data in a smaller space.

Every QR code contains three finder patterns (the large squares in three corners) that help scanners detect orientation and angle. The fourth corner has an alignment pattern for perspective correction. Between these patterns, data is encoded in a specific pattern of modules.

QR Code Types

Create any type with our QR Code Generator. For WiFi sharing specifically, try WiFi QR Generator.

Error Correction Levels

QR codes use Reed-Solomon error correction, allowing them to be read even when partially damaged or obscured:

Level H is essential when adding a logo to the center of a QR code — the logo obscures modules, and high error correction compensates.

Data Capacity

In practice, keep QR code data short. A URL under 100 characters produces a small, easily scannable code. Long URLs create dense codes that are harder to scan, especially from a distance.

Common Uses

• Payments — Alipay, WeChat Pay, UPI, and many banking apps use QR codes for transactions
• Restaurant menus — Replaced paper menus during COVID-19, now standard in many restaurants
• Product packaging — Links to manuals, warranty registration, or nutritional information
• Event tickets — Boarding passes, concert tickets, conference badges
• WiFi sharing — Guests scan to connect without typing passwords
• Business cards — vCard QR codes for instant contact saving
• Authentication — Two-factor authentication (TOTP) setup via QR code
• Inventory tracking — The original use case, still widely used in logistics

Creating QR Codes

Online Tools

Our QR Code Generator creates codes entirely in your browser — no data is sent to any server. Supports URL, text, WiFi, vCard, and custom colors.

Command Line (qrencode)

# Install
sudo apt install qrencode  # Linux
brew install qrencode       # macOS

# Generate PNG
qrencode -o qr.png "https://dl-kit.com"

# Generate SVG (scalable)
qrencode -t SVG -o qr.svg "https://dl-kit.com"

# WiFi QR code
qrencode -o wifi.png "WIFI:T:WPA;S:NetworkName;P:password;;"

# Set error correction level
qrencode -l H -o qr.png "https://dl-kit.com"

# Set size (module size in pixels)
qrencode -s 10 -o qr.png "https://dl-kit.com"

Python (qrcode library)

import qrcode

# Basic QR code
img = qrcode.make("https://dl-kit.com")
img.save("qr.png")

# Customized
qr = qrcode.QRCode(
    version=1,
    error_correction=qrcode.constants.ERROR_CORRECT_H,
    box_size=10,
    border=4,
)
qr.add_data("https://dl-kit.com")
qr.make(fit=True)
img = qr.make_image(fill_color="black", back_color="white")
img.save("qr_custom.png")

Scanning QR Codes

Most smartphone cameras now scan QR codes natively — just point the camera at the code. For scanning from image files, use our QR Code Reader.

Scanning Tips

• Ensure adequate lighting — QR codes need contrast to be read
• Hold the camera steady and at the right distance (10-30 cm for small codes)
• The entire QR code must be visible in the camera frame
• Avoid glare on glossy surfaces — tilt slightly to reduce reflection
• Damaged codes may still scan if error correction level is high enough

Design Best Practices

1. Minimum size — 2×2 cm for close-range scanning. For distance: 10 cm per 1 meter of scanning distance.
2. Quiet zone — Leave a white border of at least 4 modules around the QR code. Without it, scanners may fail.
3. Contrast — Dark modules on light background. Minimum 40% contrast difference. Avoid low-contrast color combinations.
4. Colors — Dark foreground, light background (not inverted). Red/green combinations are problematic for color-blind users.
5. Logo placement — Center only, use error correction level H, keep logo under 20% of QR code area.
6. Test before printing — Scan with at least 3 different devices/apps before mass printing.
7. Use short URLs — Shorter data = simpler QR code = easier to scan.