QR codes are on restaurant menus, product packaging, business cards, and billboards. They are one of the most successful data storage formats ever invented — yet most people have no idea how they actually work.
What is a QR code?
A QR code (Quick Response code) is a two-dimensional barcode that encodes data as a pattern of black and white squares. Unlike a 1D barcode (the kind on grocery items) that only encodes data horizontally, a QR code encodes data in both dimensions — which is why it can hold much more information.
QR codes were invented by Denso Wave in 1994 to track automotive components in Toyota factories. They became publicly available royalty-free, which is why they are so ubiquitous today.
How does a QR code work?
A QR code is divided into several functional regions:
- Finder patterns — the three square patterns in the corners. These let the scanner locate and orient the code regardless of angle.
- Alignment patterns — help correct for image distortion in larger codes.
- Data modules — the rest of the squares encode the actual data plus error correction bits.
- Quiet zone — a white border around the code that helps scanners distinguish it from surrounding content.
When you scan a QR code, your phone's camera captures the image, the QR decoder identifies the finder patterns to establish orientation, and then reads the data modules to reconstruct the encoded string — typically a URL, which the phone then opens.
What can a QR code store?
| Data type | Example use |
|---|---|
| URL | Link to website, menu, product page |
| Plain text | Short message, address |
| WiFi credentials | Auto-connect guests to WiFi |
| vCard / contact | Share phone number, email, address |
| Email address | Pre-fill email compose |
| Phone number | Tap to call |
| SMS | Pre-fill text message |
Error correction — why damaged QR codes still scan
QR codes use Reed-Solomon error correction. There are four levels:
- Level L — 7% of code can be damaged
- Level M — 15% can be damaged
- Level Q — 25% can be damaged
- Level H — 30% can be damaged
This is why adding a logo to the center of a QR code works — you are deliberately "damaging" up to 30% of the code, and the error correction recovers the missing data. Higher error correction levels make QR codes larger, which is why you pick the lowest level that meets your needs.
How to create a QR code for free
The 365tools QR Generator creates custom QR codes for URLs, WiFi networks, email addresses, phone numbers, and plain text — entirely in your browser.
- Go to the QR Generator
- Select your content type (URL, WiFi, Email, Phone, Text)
- Enter the data
- Customize colors if needed
- Download as PNG or SVG
Generate a custom QR code for free
URLs, WiFi, email, phone, text — export as PNG or SVG. No account needed.
Open QR Generator →Frequently asked questions
What does QR stand for?
QR stands for Quick Response. The format was invented by Denso Wave, a Toyota subsidiary, in 1994 to track automotive parts during manufacturing.
How much data can a QR code store?
A QR code can store up to 7,089 numeric characters or 4,296 alphanumeric characters. In practice, URLs are the most common payload. A typical URL QR code stores 50–200 characters.
Can a QR code be scanned if it is partly damaged?
Yes. QR codes have built-in error correction (up to 30% of the code can be damaged or obscured and still scan correctly). This is why you can add a logo or design element to the center of a QR code without breaking it.
Are QR codes free to generate and use?
Yes. The QR code standard is publicly available. You can generate QR codes for free and use them commercially without paying any licensing fees.
Do QR codes expire?
Static QR codes (which encode data directly) never expire. If the URL you encoded changes or goes offline, the QR code will scan but the destination won't work — the code itself is permanently valid.