What Is a QR Code?

What does QR code stand for?

QR stands for Quick Response. The format was invented in 1994 by Masahiro Hara and his team at DENSO WAVE, a Toyota group company, to track car parts on assembly lines faster than one-dimensional barcodes allowed. DENSO WAVE made the specification free to use, which is why QR codes spread to packaging, tickets, menus and payments. It is now the international standard ISO/IEC 18004. “QR Code” is a registered trademark of DENSO WAVE.

What’s inside a QR code

A QR code is a grid of dark and light squares called modules. Some parts are fixed so a scanner can find and align the code; the rest carries your data.

• Finder patterns: the three large squares in the corners. They tell the scanner where the code is and which way up it is.
• Alignment and timing patterns: smaller marks that keep the grid straight when the code is curved, tilted or printed small.
• Format information: records the error correction level and the mask pattern used.
• Data and error correction: your content, plus extra bytes that let the code be read even when part of it is damaged.
• Quiet zone: the blank margin around the code. Scanners need it to tell where the code starts.

How do QR codes work?

When you point a camera at a QR code, the phone finds the three finder patterns, works out the grid size, reads each module as dark or light, and decodes the result. Because of Reed–Solomon error correction, it can rebuild missing parts: between about 7% (level L) and 30% (level H) of the code can be damaged or covered, for example by a logo, and still scan.

What happens next depends on the content: a link opens in the browser, Wi‑Fi details offer to join the network, a vCard offers to save the contact.

How much data can a QR code hold?

QR codes come in 40 sizes called versions, from 21 × 21 modules (version 1) to 177 × 177 (version 40). The largest code at the lowest error correction holds up to:

• 7,089 digits
• 4,296 letters and numbers (uppercase alphanumeric)
• 2,953 bytes of other text, such as a long URL

In practice you want much less. More data means more, smaller modules, which are harder to print and scan. A short link fits in a small, easy-to-scan code. See QR code sizes and versions.

QR code vs barcode

Shops still use barcodes such as EAN and UPC at the checkout. You can make both: QR codes and barcodes.

Static and dynamic QR codes

A static QR code stores the content in the pattern itself. It works forever, but you can’t change it. A dynamic QR code stores a short link that redirects to your content, so you can change the destination after printing and count scans. Read the full comparison.

What QR codes are used for

• Website links on posters, packaging and ads (URL QR code)
• Restaurant menus and table ordering (menu QR code)
• Guest Wi‑Fi (Wi‑Fi QR code)
• Business cards that save a contact (vCard QR code)
• App downloads, social profiles, maps and documents

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