# What is a QR code?

> A QR code is a two-dimensional barcode that stores data as a grid of black and white squares. A camera reads the pattern and recovers the original text — usually a web address. It was invented in 1994 by Denso Wave to track car parts, and the format is free for anyone to use.

Source: https://useqr.app/docs/basics/what-is-a-qr-code · Last reviewed 2026-08-21 · UseQR is free forever, MIT licensed, no signup.

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## QR stands for "Quick Response"

The name is literal. The format was designed so a scanner could read it fast and from any
angle — unlike a supermarket barcode, which must be presented roughly the right way up.

## What is inside one

A QR code holds **text**. That is all. What makes it useful is that scanners recognise
certain prefixes and act on them:

| The text starts with | The phone offers to |
|---|---|
| `https://` | open a web page |
| `mailto:` | compose an email |
| `tel:` | dial a number |
| `WIFI:` | join a network |
| `BEGIN:VCARD` | save a contact |
| `geo:` | open a map |
| anything else | just display it |

There is no lookup, no database and no server involved in a static code. The text is
physically in the pattern.

## The parts you can see

- **Three large squares** in the corners — [finder patterns](/glossary/finder-pattern). The
  scanner uses these to locate the code and work out its orientation. The missing fourth
  corner is how it knows which way up the code is.
- **Small squares** scattered through larger codes —
  [alignment patterns](/glossary/alignment-pattern), which correct for the code being tilted
  or curved.
- **Dotted lines** between the corners — [timing patterns](/glossary/timing-pattern), a ruler
  that tells the decoder the grid spacing.
- **The blank margin** — the [quiet zone](/glossary/quiet-zone), which must be at least four
  modules wide or the code often will not be found at all.
- **Everything else** is data and error correction.

## How much it holds

At most 7,089 digits, 4,296 uppercase alphanumeric characters, or 2,953 bytes of arbitrary
text. Those are ceilings, not targets: a code holding 2,953 bytes is 177 squares across and
needs to be printed about 9 cm wide to be readable.

## Who owns it

Denso Wave invented QR codes and holds patents, but chose not to enforce them against users
of the standardised format. That decision is why QR codes became universal while comparable
proprietary 2D codes did not. "QR Code" is a registered trademark; the format itself is
described in the open standard [ISO/IEC 18004](/glossary/iso-18004) and is free to use.

## FAQ

### What does QR stand for?
Quick Response. The format was designed to be decoded fast and from any orientation, unlike the one-dimensional barcodes it was intended to replace.

### Is a QR code free to use?
Yes. Denso Wave holds patents but has declared it will not enforce them against users of the standardised format. Generating and reading QR codes costs nothing and requires no licence.

### What can a QR code contain?
Any text, up to 2,953 bytes. Scanners recognise prefixes such as https:, tel:, mailto: and WIFI: and offer the matching action; text with no prefix is simply displayed.

### Why do QR codes have three squares in the corners?
They are finder patterns. Three points define an orientation, so the scanner can work out where the code is and which way up it is. A fourth would be redundant, and adding one breaks detection.

## Try it

- https://useqr.app/url
- https://useqr.app/text
- https://useqr.app/scan