What is a QR Code?

Introduction

How QR codes work

Use cases

Types of QR codes

Implementation

Basics

Structure of a QR code

QR codes are made up largely of a grid of black and white squares (“modules”). This structure is used to encode information in binary form.

The so-called “finder patterns” (the large squares in three of the four corners of the QR code) help scanners quickly detect the code and align it correctly. Smaller markings within the code (“alignment patterns”) ensure that the content can still be read accurately, even at an angle or if the code is slightly distorted.

Lines between the finder patterns, made up of alternating black and white modules, define the grid and divide it evenly.

The grid of black and white modules contains the actual data along with additional redundancy information for error correction.

A white border called the “quiet zone” (at least four modules wide) frames the QR code to separate it from its surroundings.

Certain areas of the QR code are reserved for special information:

• Version information: Indicates the size of the grid
• Format information: Contains the error correction level and the masking pattern used
• Dark module: A single black square used as a reference point (always in the same position)

The size of a QR code depends on the amount of stored information and the chosen error correction level. A small QR code with just a few squares is usually enough for a web address, while longer texts or extensive datasets require larger grids.

A standard QR code has a minimum size of 21×21 modules and a maximum size of 177×177 modules.

The size is determined by the version number (1–40) using the following formula:

(Version number – 1) × 4 + 21

Thus, version 1 corresponds to 21×21 modules, while version 40 results in the maximum size of 177×177.

At 177×177 with the lowest error correction level, a QR code can hold up to 4,296 alphanumeric characters.

Error Correction

Error correction in QR codes ensures that information remains readable even if the code is partially damaged, dirty or poorly printed.

This is achieved through adding additional data redundancy: Alongside the actual content, the QR code also stores correction data, which is automatically used during scanning.

There are four different error correction levels, chosen depending on the application:

• Level L (Low): Restores about 7% of data, offers the highest storage capacity.
• Level M (Medium): Restores up to 15% of data, the standard for many applications.
• Level Q (Quartile): Restores up to 25% of data, often used in advertising or on packaging.
• Level H (High): Restores up to 30% of data, highly robust, suitable for industrial use or outdoor codes.

The choice of error correction level is a trade-off between data security and storage capacity: The higher the correction level, the less overall information can fit into a QR code.

Data Encoding

The actual information in a QR code – such as a web address, product number or text – is not stored directly as characters but translated into a binary format (0s and 1s). QR codes use different encoding modes depending on the type of data:

• Numeric: Digits only (0–9). Offers the highest data density and is the most space-efficient.
• Alphanumeric: Includes uppercase letters, digits and a limited set of special characters (e.g. $, %, +, -). Commonly used for product or serial numbers.
• Byte mode: Supports 8-bit characters, typically in UTF-8. Allows storage of text in almost any language.
• Kanji mode: Optimized for Japanese characters, originally developed for the Japanese market.

The data stream (bit sequence) includes the encoding mode indicator, the character count, the actual data bits, error correction information and additional padding bits.

A QR code can also combine multiple modes. For example, a product number (numeric) and a web address (alphanumeric) can be stored together in the same code.

Use Cases

Where are QR codes used?

Today, we encounter QR codes in many places:

• Marketing: Posters, packaging, brochures
• Retail: Price tags and product information
• Services: Digital menus, tickets
• Finance: Mobile payments

In addition to all the other appplications, QR codes continue to play an important role in the industry. Beyond their original use in material labeling, they are widely applied in warehouse and logistics management, order processing and production control.

Types

Other types of QR codes

The classic QR code has served as a basis for several other QR code variants that were developed to meet specific requirements:

• Greater data capacity
• Smaller space requirements
• Handling of sensitive data
• Custom designs

Micro QR Code

The Micro QR Code is a smaller variant designed for applications with very limited space, such as small components in manufacturing.

Its data capacity is limited (up to 35 digits or 21 alphanumeric characters) but sufficient for short numbers or IDs.

Unlike standard QR codes, Micro QR Codes have only one finder pattern in the top-left corner. Their size ranges from 11×11 to 17×17 modules.

Design QR Code

A Design QR Code allows the addition of graphic elements such as logos, colors and custom designs without losing its functionality.

This is made possible by taking advantage of the error correction mechanismn, which ensures the code can still be recognized by a scanner despite the added visual elements.

Design QR Codes are used primarily in marketing, in industrial contexts they play only a minor role.

A Design QR Code with a logo in the middle.

Secure QR Code

Secure QR codes can contain both a public and an encrypted data section. The encrypted data can only be read by a device that has the corresponding key.

iQR Code

iQR codes are an advanced version that not only allow for much higher data density but can also be generated in rectangular shapes.

With a maximum size of 422×422 modules, they can store significantly more data than standard QR codes. In addition, they offer higher levels of error tolerance.

Static and dynamic QR codes

With regard to the content stored, a distinction can be made between static and dynamic QR codes.

Static QR codes encode fixed content such as text or a permanent website URL.

Dynamic QR codes point to a redirect URL that leads to a specific target URL. The target URL can later be updated. They also allow insights into usage, since visitor statistics of the redirect URL can be tracked and analyzed.

Implementation

Integration of QR codes in manufacturing

With manubes, you can integrate QR code scanning into your own applications to make production processes simpler, more efficient, and more secure.

• Verify materials with a quick scan to avoid costly mix-ups.
• Scan QR codes at workstations to instantly access the right dashboards and overviews.
• Provide maintenance-related information by placing QR codes on machines.
• Optimize internal logistics by marking pallets, containers, or storage locations and linking them to software systems.

Implementation

Integration of QR codes in manufacturing

With manubes, you can integrate QR code scanning into your own applications to make production processes simpler, more efficient, and more secure.

• Verify materials with a quick scan to avoid costly mix-ups.
• Scan QR codes at workstations to instantly access the right dashboards and overviews.
• Provide maintenance-related information by placing QR codes on machines.
• Optimize internal logistics by marking pallets, containers, or storage locations and linking them to software systems.