How Are QR Codes Generated? The Technical Process Explained

Every QR code you scan—on a restaurant menu, a concert ticket, a business card—is the result of the same mathematical encoding process. The seemingly random pattern of black and white squares follows precise rules that allow any smartphone camera to decode it instantly.

Understanding how QR codes are generated won't just satisfy curiosity. It'll help you create better codes and troubleshoot when things go wrong.

The Short Version: Data → Binary → Pattern

Here's the basic process any QR code generator follows:

1. Input data - You provide a URL, text, contact info, or other content
2. Mode selection - The generator picks the most efficient encoding mode for your data type
3. Binary conversion - Your data becomes a string of 1s and 0s
4. Error correction - Redundant data is added so the code works even if damaged
5. Matrix placement - The binary data fills a grid according to strict placement rules
6. Pattern addition - Finder patterns, timing patterns, and alignment patterns are added
7. Masking - A mask is applied to ensure the code is scannable

The result is the pattern you see—a matrix of dark and light modules that any QR scanner can read.

Step-by-Step: How Your Data Becomes a Code

1. Encoding Mode Selection

QR codes support four encoding modes, each optimized for different data types:

Notice how numeric mode is most efficient—a phone number takes less space than a URL of the same length. Smart generators automatically select the optimal mode for your data.

2. Data Encoding to Binary

Your data converts to binary based on the selected mode. For example, in numeric mode:

• Digits are grouped in threes
• Each group converts to a 10-bit binary number
• "123" becomes "0001111011"

In byte mode (used for most URLs), each character converts to its 8-bit ASCII value:

• "A" becomes "01000001"
• "1" becomes "00110001"
• The full URL becomes a long string of binary digits

3. Error Correction Encoding

This is where QR codes get interesting. The Reed-Solomon error correction algorithm adds redundant data that allows recovery even when parts of the code are damaged or obscured.

There are four error correction levels:

Higher error correction means more redundant data—and less room for your actual content. A URL that fits at Level L might not fit at Level H in the same size code.

4. Building the Matrix

The binary data (your content plus error correction) fills the QR code matrix according to specific placement rules. But before that data goes in, the structural elements are placed:

Finder patterns - The three large squares in the corners. These help scanners locate and orient the code. They're always the same: a 7×7 pattern with a dark center.

Timing patterns - Alternating dark and light modules between the finder patterns. These help the scanner determine module size.

Alignment patterns - Smaller locator squares in larger codes (version 2 and above). They help scanners handle perspective distortion.

Format information - 15 bits near the finder patterns that tell the scanner which error correction level and mask were used.

Version information - In codes version 7 and above, additional bits specify the exact code version.

After these elements, your encoded data fills the remaining space in a specific zig-zag pattern, starting from the bottom-right corner.

5. Applying the Mask

Here's something most people don't know: raw QR codes often have problematic patterns—large areas of the same color, or patterns that resemble finder patterns. These can confuse scanners.

The solution is masking. The QR specification defines eight mask patterns, each a mathematical formula that XORs (flips) specific modules. The generator tests all eight masks and selects the one that produces the most scannable result based on penalty rules.

This is why the same data can produce slightly different-looking codes from different generators—they might select different masks. Both codes are equally valid.

Static vs. Dynamic: Different Generation, Different Results

The generation process above applies to all QR codes. The difference between static and dynamic codes comes earlier—in what data gets encoded.

Static Code Generation

Your actual URL (or text, or contact info) goes through the encoding process. The final destination is embedded directly in the code pattern.

Input: https://example.com/menu
Result: Code pattern encodes "https://example.com/menu"

Pros:

• Works forever (no dependency on external servers)
• Fastest possible scanning (direct to destination)
• Free to generate anywhere

Cons:

• Can't be edited after creation
• Can't track scans
• Long URLs create dense, harder-to-scan codes

Dynamic Code Generation

A short redirect URL goes through the encoding process. Your actual destination is stored in a database, and the redirect URL points there.

Input: https://example.com/my-very-long-url-path/with-parameters
Result: Code pattern encodes "https://qrc.example/abc123"
        Redirect server maps abc123 → your actual URL

Pros:

• Shorter encoded URL = simpler, more reliable codes
• Destination can be changed without reprinting
• Scans can be tracked and analyzed

Cons:

• Depends on redirect server availability
• Requires ongoing service (usually paid)
• Your codes die if you stop paying (or the service shuts down)

What Makes a Good vs. Bad QR Code

Understanding generation helps you create better codes:

Module Size and Density

More data = more modules = smaller module size. If modules get too small relative to print size, scanning fails. Rules of thumb:

• Minimum print size: Each module should be at least 0.3mm for reliable scanning
• Practical minimum: For a Version 4 code (33×33 modules), minimum size is about 2cm × 2cm
• Environmental factors: Outdoor use, distance scanning, or poor lighting require larger codes

Error Correction Choice

Match error correction to your use case:

• Level L: Digital displays, clean indoor environments
• Level M: General printing, business cards, packaging
• Level Q: Industrial labels, warehouse environments
• Level H: Outdoor signage, codes with logo overlays

URL Optimization

Before generating, optimize your URL:

• Use your shortest domain
• Avoid unnecessary parameters
• Consider whether tracking parameters add value
• If the URL is long, consider whether you need dynamic codes

The Generation Process is Standardized

Here's something the QR code industry doesn't want you to think about too hard: the generation algorithm is standardized. ISO/IEC 18004 specifies exactly how QR codes should be created. Any compliant generator produces functionally identical output for the same input.

This means:

• "Premium" static codes aren't better than free ones
• The same URL generates an equivalent code anywhere
• You're paying for features (editing, tracking, management)—not better code generation

Frequently Asked Questions

Why do different generators create different-looking codes for the same URL?

Two reasons: mask selection and style options. Different generators might choose different masks (all equally valid), and many add visual customization like colors or logos. The underlying encoded data is identical.

Can I generate QR codes without an internet connection?

Yes. Static code generation happens entirely client-side—no internet required. The math runs in your browser. Dynamic codes require a server to create the redirect mapping, so they need connectivity.

Is there a limit to how much data a QR code can hold?

Yes. The largest QR code (Version 40, 177×177 modules) can hold about 7,089 numeric characters, 4,296 alphanumeric characters, or 2,953 bytes at the lowest error correction level. Practical limits are much lower for reliable scanning.

Why do some QR codes scan faster than others?

Simpler codes (fewer modules, higher contrast, cleaner print) scan faster. A short URL with medium error correction in a clean black-and-white design will scan almost instantly. A long URL with custom colors at high error correction may take longer.

Can QR codes contain malware?

QR codes themselves are just data—they can't execute code. But they can contain URLs pointing to malicious sites, just like any link. The danger isn't the QR code; it's blindly trusting where it leads. Always check the URL preview before proceeding.

Generate Your QR Codes

Ready to create codes with this knowledge in mind?

For static codes (permanent, free):

• URL QR codes - Any webpage
• WiFi QR codes - Network credentials
• vCard QR codes - Contact information
• Text QR codes - Plain text messages

No account needed. Your data encodes directly—we don't insert redirects or tracking on free codes.

For dynamic codes with editing and tracking: View our pricing - Transparent costs, no scan limits, no gotchas.