What is a QR code?
Author: Domeny.ForSale editorial team Published
In brief: A QR code is a two-dimensional code that stores information in a pattern of light and dark squares. Scanning it with a phone lets you read, for example, a website address, contact details or plain text. Reading the code itself does not require internet access, but a connection is usually needed to open the website whose address it contains.
How does a QR code work, and what can it contain?
QR stands for Quick Response. Unlike a traditional barcode, which consists of parallel bars, a QR code stores data in two dimensions. This allows it to hold more information in a small area.
The distinctive large squares in three corners help the reader recognise the code’s position and orientation. The software analyses the remaining squares and reconstructs the stored data. Error correction allows the code to be read despite partial damage, but does not guarantee that it will work regardless of dirt or obstructions.
A QR code can contain, among other things:
- a website address, or URL;
- text, such as a product identification number;
- a digital business card with contact details;
- a Wi-Fi network name and the details needed to connect;
- data for composing an email or text message.
The app reading the code determines how to present the data and which action to suggest. A code containing a website address does not contain the entire website — it is more like a shortcut to it, similar to a link in a message.
How do you scan a code with your phone?
On many modern phones, you simply open the camera and point it at the code. Once the device recognises the content, it displays a notification or button. You do not need to take a photo: usually, you just tap the option to open the link or display the information.
If the camera does not respond, check whether QR scanning is enabled in its settings. You can also use a built-in scanner or a trusted app. The exact steps depend on your phone model and operating system version.
If you have trouble reading the code, ensure there is enough light, eliminate glare and adjust the distance between the phone and the code. The entire square, including its blank margin, should fit within the frame. A code displayed on the same phone’s screen can sometimes be read from a screenshot in the photos app; availability of this feature depends on the device.
Static vs dynamic codes: which should you choose?
A static code contains the target data directly, such as the address https://example.com/menu. Once it has been printed, the information stored in its squares cannot be changed. However, you can change the content of the website at that address — this does not require a new code.
A dynamic code is a common name for a solution in which the QR code first leads to an intermediary address. The service handling that address redirects the user to the chosen destination. You can change the redirect destination in the service’s dashboard without replacing the printed code.
| Need | Usually the right choice |
|---|---|
| A permanent website address or Wi-Fi details | Static code |
| Changing the destination address after materials have been printed | Dynamic code |
| Reducing dependence on a QR generator | Static code pointing to your own domain |
Example: a restaurant prints a code on its tables. If the menu is always available at /menu on its own domain, a static code is enough, even if prices and dishes change daily. A dynamic code is useful when the owner wants to direct guests to a completely different address later.
Dynamic code services may offer scanning statistics, usage limits or paid plans. Before choosing one, check the official pricing and terms to find out what happens to the redirect when the subscription ends and what data is collected. A static QR code itself has no expiry date, although the website it points to may stop working.
How do you create a code that can be read?
To generate a code, you need content and a tool that converts it into an image. Do not send confidential data to an arbitrary generator. If the code is to contain a Wi-Fi password, consider a tool that works locally, without sending data to a server.
The safest process for preparing your material is short:
- Enter the final data and check that it is correct.
- Maintain strong contrast, preferably dark squares on a light background, and a blank margin around the code.
- Do not stretch the image or cover the squares with decorations.
- Test the code on several phones and, for print, also on a sample at the intended size.
The more data you store, the denser the pattern may become. There is no single size suitable for every situation: a code on a business card and one on a poster viewed from several metres away need different dimensions. Next to the code, include information about its purpose and a readable address as an alternative.
Is scanning QR codes safe?
A QR code does not verify the trustworthiness of the information it contains. It may lead to a fake login page, a suspicious file or a form designed to steal data. A scammer may also stick their own code over genuine material, for example at a parking meter.
Before opening a link, check the address preview, and before entering a password or making a payment, check the domain and context. The padlock symbol and HTTPS indicate an encrypted connection, not that the website owner is honest. If in doubt, open the official app or type a known address yourself.
If you are creating your own code, start by deciding what the recipient should see after scanning it. Then check the entire process on a phone: not just whether the code can be read, but also whether the destination page works and is easy to read.
See also: What is Apache?
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