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GlossarySharing and scanning

What Is a QR Code and How Does It Work?

A QR code (Quick Response code) is a two-dimensional barcode, a square grid of dark and light modules, that stores text such as a web address and can be read by a phone camera. Unlike a traditional barcode it holds data in both directions and still scans when partly damaged or obscured.

What Is Inside the Square

The pattern is encoded text. Three large squares in the corners tell a scanner where the code is and which way up it is, and the remaining modules hold the data along with error-correction information. The text can be a web address, a block of contact details, a phone number or plain words. When a phone camera reads the pattern it decodes the text and then acts on its type, so a web address opens a page and a contact offers to be saved.

Why a Damaged Code Still Scans

QR codes carry redundancy in the form of error correction, which is why they survive a scuff, a crease or a logo placed in the middle. There are four levels, which recover roughly 7, 15, 25 or 30 per cent of the code. Higher levels cope with more damage but need a denser pattern for the same data. For a business card the sensible approach is to keep the encoded text short so the pattern stays sparse and lets a higher level fit comfortably.

The Quiet Zone and Contrast

A scanner needs a blank margin around the code, called the quiet zone, to tell where the code ends and the surroundings begin. Four modules wide is the usual guidance. Printing a code too close to text, an edge or a fold is a common reason it fails. Dark modules on a plain light background remain the most robust combination across phones and lighting.

What It Means for a Card

A QR code on a card does one job: get a phone to the right place without typing. A short link makes a small, forgiving pattern, and a link that you can repoint means the printed code does not age. Those two ideas, a short link and a repointable one, are the reason for the dynamic QR code, and the reason every card here uses one.

Frequently asked questions

What does QR stand for?

Quick Response. The format was designed to be read quickly by a scanner and to hold more than a one-dimensional barcode can.

Do QR codes expire?

The pattern itself never does. What can stop working is the destination: a code that links to a page works only while that page and its link still exist.

Do I need an app to scan a QR code?

Not on a current iPhone or Android phone, where the built-in camera reads codes and offers to open what it finds.

Keep reading

Related terms

Dynamic QR CodeA dynamic QR code encodes a short, fixed redirect link rather than the destination itself, so the destination can be changed at any time without altering or reprinting the code. Because the printed pattern never changes, a dynamic code can be edited after printing and can count its scans.Static QR CodeA static QR code encodes its destination or data directly in the pattern, so the code can never be edited and no service is needed for it to work. Whatever was encoded on the day it was generated is what every scan returns, for as long as the code remains legible.QR Code ScanningQR code scanning is the act of pointing a phone camera at a QR code so the phone reads the pattern and acts on what it holds, usually by offering to open a web address. Modern iPhones and Android phones do this in the built-in camera app, with no separate scanner required.QR Code Business CardA QR code business card is a business card whose contact details are reached by scanning a printed QR code. The code can either encode the details directly, which fixes them permanently, or point at a contact page, which keeps them editable after printing.

Put this into practice with your own card

Put your details on one card page, share it by link or QR code, and change them whenever they change. The printed code keeps working. No credit card required to start.

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