What is a QR Code? Complete Guide
QR codes (Quick Response codes) are two-dimensional barcodes that can store various types of information. When scanned with a smartphone camera, they instantly provide access to websites, contact information, WiFi credentials, and more.
History of QR Codes
QR codes were invented in 1994 by Denso Wave, a subsidiary of Toyota, to track automotive parts during manufacturing. The name "QR" stands for "Quick Response," referring to the code's ability to be read quickly by scanners.
Unlike traditional barcodes that can only be read in one direction, QR codes can be scanned from any angle. This made them ideal for high-speed manufacturing environments where parts moved quickly past scanners.
How QR Codes Work
QR codes encode data using a pattern of black and white squares arranged on a grid. The code contains several key components:
- Finder patterns: The three large squares in the corners help scanners locate and orient the code.
- Alignment patterns: Smaller squares that help with accuracy, especially for larger codes.
- Timing patterns: Alternating black and white modules that define the grid structure.
- Data area: The remaining modules encode the actual information.
- Error correction: Redundant data that allows the code to be read even if partially damaged.
Types of QR Codes
URL QR Codes
Link to websites, landing pages, or online resources
WiFi QR Codes
Share network credentials for instant connection
vCard QR Codes
Store contact information for easy saving
Email QR Codes
Open email compose with pre-filled fields
Phone QR Codes
Initiate phone calls with one scan
SMS QR Codes
Open messaging app with pre-filled text
Location QR Codes
Share GPS coordinates for navigation
Event QR Codes
Add calendar events to phones
Error Correction Levels
QR codes include error correction data that allows them to be read even when partially damaged or obscured:
| Level | Recovery Capacity | Best For |
|---|---|---|
| L (Low) | ~7% | Clean environments, maximum data |
| M (Medium) | ~15% | General use, good balance |
| Q (Quartile) | ~25% | Outdoor use, some damage expected |
| H (High) | ~30% | Logo overlays, harsh conditions |
Best Practices
- Size appropriately: Minimum 2x2 cm for close scanning, larger for distance
- Maintain contrast: Dark modules on light background works best
- Leave quiet zone: White space around the code (at least 4 modules)
- Test before printing: Always scan your code to verify it works
- Use appropriate error correction: Higher for logos or harsh environments