QR codes

A QR code (Quick Response) is a two-dimensional barcode capable of storing up to 4,296 alphanumeric characters — far more than the 20–25 characters of traditional linear barcodes. It can be read by any smartphone camera and can contain varied information: URLs, text, contacts, payment data or WiFi connections.

Its matrix structure of black and white modules incorporates error correction that allows data to be recovered even if up to 30% of the code is damaged or obscured. This makes them particularly reliable for physical environments where codes may wear or be printed on irregular surfaces.

History & evolution

The QR code was invented in 1994 by Masahiro Hara, an engineer at Denso Wave (a Toyota subsidiary), to track vehicle parts on assembly lines. The decision to keep the patent royalty-free was crucial: any manufacturer could implement readers without paying licences, which drove mass adoption.

Japan was the pioneer: by 2002 QR codes were already used for mobile payments and marketing. Western countries took a decade to adopt them widely, mainly because reading them required a dedicated app — a barrier that disappeared when iOS and Android integrated the reader directly into the native camera.

The final acceleration came with the COVID-19 pandemic (2020): restaurants, transport and institutions adopted digital menus and documents via QR to avoid shared surfaces. Global usage grew 300% in two years, establishing QR codes as permanent digital infrastructure.

Best practices

Creating effective QR codes requires considering technical factors that directly affect their readability:

Choose the right error correction level. QR codes offer 4 levels: L (7%), M (15%), Q (25%) and H (30%). Use H if the code will be printed on irregular surfaces, exposed to wear, or will incorporate a logo in the centre.

Respect minimum size and contrast. The recommended minimum size is 2×2 cm. Use black on white: colour inversions reduce success rates by up to 40%.

Maintain the quiet zone. A white margin of at least 4 modules around the QR code is required. Without it, many readers fail to detect the code boundaries.

Test with multiple devices. Always verify readability with several phone models and lighting conditions before publishing or mass-printing.

Use cases

QR codes have transformed many sectors. Hospitality was among the first: digital menus reduced printing costs and allow instant price or dish updates. The events industry uses QR for tickets with real-time validation, eliminating counterfeiting. Luxury brands embed them in labels to verify product authenticity via blockchain systems.

In museums and cultural spaces, QR codes next to artworks link to audio guides, videos and augmented reality. Digital business cards in vCard format allow sharing a full contact with a single scan. For payments, Alipay and WeChat process hundreds of millions of QR transactions daily, while in Europe the EPC QR format is used for instant bank transfers.

Curiosities

  • Denso Wave chose not to exercise its patent rights over the QR code, enabling its free global adoption without any licence costs.
  • A QR code can still be read correctly even if 30% of its content is damaged, thanks to the Reed-Solomon error correction system.
  • The world's largest QR code, covering 36,000 m², was created in a Canadian corn field in 2022 and was visible from orbiting satellites.
  • In 2020, during the pandemic, QR code usage increased by 300% worldwide in less than six months, cementing them as everyday digital infrastructure.

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