What a QR code is

A QR (Quick Response) code is a two-dimensional matrix barcode created in 1994 by the Japanese company Denso Wave to track automotive parts quickly. Unlike a traditional barcode that stores data in one horizontal direction only, a QR code stores data both horizontally and vertically.

That 2D structure lets it hold far more data in the same area. A typical 1D barcode holds around 20 characters, while a QR code can store up to 7,089 numeric characters — or close to 1,800 double-byte characters such as Korean or Chinese.

How a QR code is read

A scanner (or phone camera) first locates the three large squares in the corners — the finder patterns. Using these three points it corrects the code's orientation and tilt, which is why a QR code still scans even when it is rotated or photographed at an angle.

Once positioned, the scanner converts the black and white modules (small cells) into 0s and 1s and reconstructs the original text, number, or URL according to a fixed set of rules. It feels instant, but internally it goes through alignment, mask removal, and error correction.

Inside a QR code

A QR code is made of (1) finder patterns that establish orientation, (2) alignment patterns that fix coordinates in larger codes, (3) timing patterns that set the row and column reference, (4) format information that stores the version and error correction level, and (5) the data plus error-correction region.

The data region holds not only the original information but also error-correction codes, so the content can be recovered even if part of the code is dirty or covered. How resistant it is to damage is controlled by the error correction level (L, M, Q, H).

Where they are used

Originally used for manufacturing and logistics, QR codes spread into everyday life after smartphones became common — payments, business cards, WiFi access, restaurant menus, event tickets, and marketing landing pages.

On this site, the "Create QR" tab lets you build URL, text, WiFi, email, phone, and SMS QR codes and download them as PNG or SVG, while the "Scan QR" tab reads QR codes directly from an image or your camera.