Definition:
A QR code is a two-dimensional barcode made of light and dark modules arranged in a matrix. It encodes data that a camera or compatible reader can interpret and present as an action or content, such as opening a URL, displaying text or starting a configuration process.
QR stands for Quick Response. Denso Wave developed the system in 1994 to identify components in industrial processes, but its use later expanded to payments, tickets, identification, access to information and connections between physical media and digital services.
How a QR code works
The pattern contains areas that enable a reader to locate it, determine its orientation and interpret the matrix. Data is converted into a binary sequence and distributed across the modules together with format and error-correction information. The reader reconstructs that data; the content does not have to be a web page.
The format has 40 versions with matrices of increasing size. Capacity depends on the version, character type and error-correction level. Error correction can restore some information if the symbol is dirty or damaged, although a higher level leaves less space for data. Denso Wave documents these features and the four available correction levels.
Information a QR code can contain
A QR code can directly store different types of data. The reading application determines which action it offers after scanning. Common contents include:
- Web addresses: A URL that opens a page, form, download or media resource.
- Text: Messages, identifiers, short instructions or other readable information.
- Contact details: Fields that a compatible application can turn into a contact.
- Network configuration: The name, security method and password of a Wi-Fi network.
- Communication actions: Data for preparing an email, text message or call, which the device must confirm.
- Payment, access or authentication information: Structured data whose use depends on compatible services and applications.
The code carries the encoded data, but it does not guarantee that a destination exists, is safe or will remain available. When it contains a web address, subsequent operation depends on the server, connection and destination application.
Static and dynamic QR codes
The distinction between static and dynamic describes how the content is managed, rather than two visually different forms of the standard:
- Static QR code: Contains the final information, such as text or a URL. Changing it requires a new symbol.
- Dynamic QR code: Usually contains a short URL managed by a redirect service. The provider can change its destination or record scan events without replacing the image, as long as the redirect remains active.
A dynamic QR code depends on its provider and may be subject to limits, fees or expiry. A static QR code does not require that intermediary, although a linked resource can still change or become unavailable.
Uses and measurement
QR codes connect objects, documents or screens with digital information or actions. Their applications include:
- Products and inventory: Identification, traceability, instructions and information associated with an item. The commercial migration to two-dimensional codes relies on specific standards; a generic QR code does not automatically replace every barcode.
- Tickets and credentials: Access validation for transport, events, buildings or services.
- Payments: Transfer of data used to start a transaction within a compatible system.
- Retail, museums and hospitality: Access to menus, records, audio guides or additional information.
- Proximity marketing: Connection between physical media and a campaign, promotion or mobile experience.
- Access and configuration: Login, device pairing or service configuration, depending on the protocol in use.
A scan does not always create a metric by itself. If the QR code opens a website, the visit can be measured at the destination; UTM parameters help identify the campaign. Dynamic QR services can also record events, but their figures depend on each provider’s methodology and must be handled under the applicable privacy obligations.
Readability, customization and security
Readability depends on design, printing, environment and device. The main factors include:
- Contrast: Modules need to stand out clearly from the background.
- Quiet zone: Clear space around the symbol helps the reader detect its boundaries.
- Size and distance: The code needs to be large enough for the scanning distance and data density.
- Surface and quality: Reflections, curvature, blur or damage can hinder recognition.
- Customization: Colours, frames and logos can be added without obscuring essential patterns or exceeding the correction capacity.
- Destination: The link and action need to be tested on the intended devices and under the expected conditions.
A person cannot determine the destination simply by looking at the pattern. A code can conceal a fake website or be covered by another code, a technique related to phishing. A QR code therefore does not authenticate its sender: an application may display the URL before opening it, but trust depends on the origin of the code and its actual destination.