What is a QR code?
A QR code is a two-dimensional barcode that stores text a phone camera can read. Point a camera at one, and it decodes the hidden text — usually a web link — and acts on it. That's the whole concept. This page explains what the squares mean, what a code can hold, and why the format won.
The definition
QR stands for Quick Response. A QR code is a grid of black and white squares — each square is called a module — that encodes text. The arrangement of dark and light modules is the data. When you scan a code, software locates the grid, reads the pattern of modules, applies error correction, and reconstructs the original text. If that text is a web address, your phone offers to open it.
Crucially, a QR code doesn't "contain a website." It contains text. That text might be a URL, but it might equally be a Wi-Fi password, a phone number, or a contact card. The scanner decides what to do based on what the text looks like. Understanding this one fact explains every use case: choosing a QR code "type" really means choosing what text to encode.
The three large squares in the corners are finder patterns — they let a scanner locate and orient the code from any angle. The rest of the grid holds your data plus redundancy for error recovery. The full anatomy is covered in how QR codes work.
What a QR code can hold
The data capacity depends on the code's version (its physical size, from 21×21 modules up to 177×177) and the character set. At the largest version with the lowest error correction, a single QR code can store up to roughly:
| Data type | Maximum capacity |
|---|---|
| Numeric (digits) | 7,089 characters |
| Alphanumeric | 4,296 characters |
| Binary / bytes | 2,953 bytes |
| Kanji | 1,817 characters |
Those are theoretical maximums. In practice you want far less: the more data you pack in, the denser and harder-to-scan the code becomes. A short link of 20–40 characters produces a coarse, robust pattern; a long contact card produces a fine grid that demands a steadier camera and cleaner print. For real-world reliability, keep payloads short — see design best practices.
Why a QR code, not a regular barcode
A traditional retail barcode is one-dimensional: data is read across a single row of vertical bars, which limits it to about a dozen digits — enough for a product number that points to a database entry. A QR code is two-dimensional: it stores data both across and down, so it holds thousands of characters and can carry the actual content rather than just a lookup key. It also includes built-in error correction, so it still scans when smudged, creased, or partially covered. The full comparison is in QR code vs barcode.
How a phone reads one
Modern phones need no special app. The camera app on iPhone (iOS 11 and later) and on current Android versions detects QR codes automatically: point the camera, and a tappable notification appears. Behind the scenes the software finds the three finder patterns, corrects for angle and distortion, samples each module as dark or light, runs the error-correction math to fix any misreads, and decodes the result back into text. The whole process takes a fraction of a second. Step-by-step instructions for every platform are in how to scan a QR code.
Where QR codes came from
The format was invented in 1994 by Denso Wave, a Japanese automotive-parts subsidiary of Toyota, to track components on the manufacturing line faster than 1D barcodes allowed. Denso Wave holds the patents but chose to keep the standard open and license-free, which is a major reason QR codes spread worldwide. They moved from factories to marketing, then to payments, and finally became ubiquitous when smartphone cameras gained native scanning. The longer story is in the history of QR codes.
See it for yourself
Type any text or link and watch the modules rearrange in real time. The readout shows the version, module count, and error-correction level as you go.
Open the generatorFrequently asked questions
What does QR stand for?
QR stands for Quick Response. The format was designed by Denso Wave in 1994 to be read quickly, from any angle, even when partly damaged.
What can a QR code store?
Any text — web links, Wi-Fi credentials, contact cards, phone numbers, email drafts, plain text and more. A single code can hold up to about 4,296 alphanumeric characters at the largest size and lowest error correction, though smaller payloads are far more reliable.
Is a QR code the same as a barcode?
A QR code is a type of barcode, but a two-dimensional one. A traditional barcode stores a few digits in a row of lines; a QR code stores data in a grid of squares both horizontally and vertically, holding far more. See QR code vs barcode.
Do QR codes cost anything to make?
No. The QR code format is an open standard and free to use. A static QR code you generate yourself, like the ones here, costs nothing and never expires. Some providers charge for dynamic codes and analytics — see free vs paid generators.