How Do QR Codes Work?
QR codes are everywhere today. You can find them on restaurant tables, product packaging, event tickets, payment terminals, advertisements, and even cryptocurrency wallets.
Despite their popularity, many people do not know how QR codes actually work. A QR code may look like a random collection of black and white squares, but it is actually a highly efficient way of storing information that can be read in seconds by a smartphone camera.
In this guide, you'll learn what QR codes are, how they store information, how phones scan them, and why they have become one of the most widely used technologies in the world.
What Is a QR Code?
QR stands for Quick Response.
The QR code was invented in 1994 by Denso Wave, a Japanese company that was part of the Toyota Group. It was originally designed to track automotive parts during manufacturing.
Unlike traditional barcodes that store information in a single direction, QR codes store information in two dimensions. This allows them to hold much more data while remaining easy to scan.
Barcode vs QR Code
| Feature | Barcode | QR Code |
|---|---|---|
| Dimensions | 1D | 2D |
| Data Capacity | Low | High |
| Error Correction | Limited | Strong |
| Scan Speed | Fast | Very Fast |
What Information Can a QR Code Store?
QR codes can store many different types of information:
- Website URLs
- Plain text
- Phone numbers
- Email addresses
- SMS messages
- WiFi credentials
- Contact information
- Cryptocurrency wallet addresses
- Location coordinates
- Digital menus
A QR code does not understand what the information means. It simply stores data. The device scanning the QR code decides what action should be taken.
How Information Is Stored
Every character is converted into binary data. Binary uses only two values:
- 0
- 1
The binary data is then encoded into the black and white modules that make up the QR code.
HELLO H = 01001000 E = 01000101 L = 01001100 L = 01001100 O = 01001111
The Different Parts of a QR Code
Finder Patterns
The three large squares found in the corners help scanners determine the orientation of the QR code.
Alignment Patterns
These smaller squares help scanners compensate for perspective distortion.
Timing Patterns
Alternating black and white modules help scanners understand the grid structure.
Data Area
This section contains the actual encoded data.
Quiet Zone
The empty white border around a QR code helps scanners detect its boundaries.
How Smartphones Scan QR Codes
- Camera captures the image.
- Finder patterns are detected.
- Orientation is calculated.
- Perspective distortion is corrected.
- Binary data is extracted.
- Error correction is applied.
- Information is decoded.
- The appropriate action is performed.
Why Damaged QR Codes Still Work
QR codes use a technology called Reed-Solomon Error Correction.
This means extra recovery information is stored inside the QR code. Even if part of the code is damaged, scanners can often reconstruct the missing information using math. How cool is that.
| Level | Recovery |
|---|---|
| L | 7% |
| M | 15% |
| Q | 25% |
| H | 30% |
Are QR Codes Safe?
The QR code itself is not dangerous. However, the destination can be.
- Verify website URLs before opening them.
- Avoid scanning unknown QR codes.
- Be cautious of phishing websites.
- Check domains carefully before entering passwords.
Try QR Codes Yourself
Now that you understand how QR codes work, you can create your own QR codes for websites, WiFi networks, contact cards, email addresses, cryptocurrency wallets, and more.
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