QR Codes Demystified: Understanding and Building Projects

2 min read
tutorial
qr-code
javascript

QR Codes Demystified: Understanding and Building Projects

QR codes are everywhere - from restaurant menus to payment systems. But how do they actually work? Let's break it down and build something with them.

What is a QR Code?

QR stands for "Quick Response". It's a two-dimensional barcode that can store various types of data:

  • URLs
  • Text
  • Contact information
  • WiFi credentials
  • And much more

How QR Codes Store Data

A QR code consists of several key components:

1. Finder Patterns

The three large squares in the corners help scanners identify and orient the code.

2. Alignment Patterns

Smaller squares that help correct for distortion when the code is printed on curved surfaces.

3. Timing Patterns

Alternating black and white modules that help determine the size of the data modules.

4. Data and Error Correction

The actual encoded data, along with error correction information that allows the code to be read even if partially damaged.

Error Correction Levels

QR codes have four error correction levels:

  • L (Low): ~7% recovery capacity
  • M (Medium): ~15% recovery capacity
  • Q (Quartile): ~25% recovery capacity
  • H (High): ~30% recovery capacity

Higher error correction means more redundancy, allowing the code to be read even if damaged.

Building a QR Code Generator

Here's a simple approach using JavaScript:

// Using a library like 'qrcode'
import QRCode from 'qrcode';
 
async function generateQR(text) {
  try {
    const url = await QRCode.toDataURL(text);
    return url;
  } catch (err) {
    console.error(err);
  }
}

Practical Applications

  1. Payment Systems: UPI, PayPal, etc.
  2. Authentication: Two-factor authentication
  3. Ticketing: Event tickets, boarding passes
  4. Marketing: Product information, promotional links
  5. Contact Sharing: vCards

Conclusion

QR codes are a powerful tool for encoding and sharing information quickly. Understanding how they work opens up possibilities for creating innovative applications.

Check out my QR Code Playground to experiment with QR code generation!