What Is a QR Code? How It Works and What You Can Use It For
Published · 4 min read
Learn what a QR code is, how much data it can hold, why it still scans when partly damaged, and the most popular ways businesses use QR codes today.
QR codes are everywhere: on receipts, café menus, product packaging, train tickets and payment terminals. But what exactly is a QR code, how much information can it hold, and why does it still work when a corner is scratched? This guide explains it in plain language, so you can create a code that works the first time.
What is a QR code?
QR stands for Quick Response. It is a two-dimensional barcode invented in 1994 by Masahiro Hara at Denso Wave, a Toyota group company in Japan, to track car parts in factories. A classic barcode is read in one direction only; a QR code stores data both horizontally and vertically, so it holds far more information in the same space.
Today the QR code is an international standard (ISO/IEC 18004) and royalty-free: anyone can create and read QR codes without paying a licence fee.
The anatomy of a QR code
Look closely and you will see several parts, each with its own job:
- Three large squares in the corners (finder patterns) tell the camera it is looking at a QR code and which way is up, even if you hold the phone at an angle.
- A small alignment square helps the reader cope with curved surfaces and skewed photos.
- Timing patterns, rows of alternating black and white modules, let the reader count the grid correctly.
- The data area contains your content plus error-correction data.
- The quiet zone, a blank margin at least four modules wide, separates the code from its surroundings.
How much data can a QR code hold?
There are 40 QR code versions. Version 1 is the smallest at 21 × 21 modules; version 40 is the largest at 177 × 177. At the lowest error-correction level, version 40 can store up to:
| Data type | Maximum capacity |
|---|---|
| Numeric only | 7,089 characters |
| Alphanumeric (upper case) | 4,296 characters |
| Binary (UTF-8) | 2,953 bytes |
In practice, the longer the content, the denser the code and the harder it is to scan when printed small. A short link or a dynamic QR code keeps the pattern open and easy to read.
Why does a damaged QR code still scan?
QR codes use Reed–Solomon error correction, with four levels to choose from:
| Level | Recovers roughly | Best for |
|---|---|---|
| L (Low) | 7% of the data | Screens, clean environments |
| M (Medium) | 15% of the data | The default for most uses |
| Q (Quartile) | 25% of the data | Outdoor print, scuffed surfaces |
| H (High) | 30% of the data | Codes with a logo in the middle |
That is why you can place a logo in the centre of a QR code and it still works, as long as you choose level H and keep the logo reasonably small.
What can you use QR codes for?
A QR code can hold different kinds of content, and each one makes the phone do something different:
- Open a website: a URL QR code for your homepage, online shop or survey.
- Join WiFi: guests scan and connect without typing a password. See our guide to WiFi QR codes.
- Save a contact: a vCard QR code on your business card.
- Call, text, email or start a WhatsApp chat.
- Get directions: a location QR code opens Google Maps.
- Get paid: PayPal or crypto wallet QR codes.
- Follow you on social media, download your app, or add an event to the calendar.
Are QR codes safe?
A QR code is just a way of storing data; it cannot contain a virus by itself. The risk is the link inside it. Scammers sometimes stick fake QR codes over real ones on parking meters or restaurant tables to send people to phishing pages. Always check the address your phone shows before opening it, especially if the page asks you to log in or pay. Read more in how to scan a QR code safely.
Create your own QR code in one minute
- Open the free QR code generator.
- Choose a type: link, WiFi, vCard, location and more.
- Enter your content, change the colours, pick a frame and add your logo if you like.
- Download a PNG for the web or an SVG for sharp printing.
Before printing in bulk, read our QR code printing tips so every code scans first time.