A QR code (Quick Response code) is a 2D barcode invented by Denso Wave in 1994 that stores data in a grid of black and white squares. Smartphone cameras can decode them instantly. QR codes typically store URLs but can encode any text up to ~3KB.

How much data can a QR code store?

A QR code can store up to 7,089 numeric characters, 4,296 alphanumeric characters, or 2,953 binary bytes at the highest capacity version. In practice, most QR codes contain short URLs.

What is error correction in QR codes?

QR codes have four error correction levels — L (7%), M (15%), Q (25%), H (30%) — indicating how much of the code can be damaged or obscured and still be readable. Higher correction means larger codes. Use H if you want to add a logo in the centre.

What is a QR Code?

A QR code (Quick Response code) is a 2D barcode that stores data in a matrix of black and white squares. Smartphone cameras decode them instantly — they most commonly store URLs.

Structure

A QR code contains finder patterns (the three square corners), timing patterns, format information, and data modules. The three corner squares allow scanners to detect the code's position and orientation regardless of the angle it's photographed at.

Error Correction Levels

L (Low) — 7% of modules can be damaged. Smallest code.
M (Medium) — 15% recoverable. Most common default.
Q (Quartile) — 25% recoverable.
H (High) — 30% recoverable. Use this when adding a logo overlay.

Common Uses

Links on print media (posters, business cards, packaging)
Restaurant menus and contactless payments
Event ticketing and boarding passes
Wi-Fi network credentials
App download links
Two-factor authentication (authenticator apps scan QR codes to set up TOTP)

Generate a QR code from any text or URL: Open QR Code Generator →

Frequently Asked Questions

How much data can a QR code hold?

Up to 7,089 numeric characters or 4,296 alphanumeric characters at the highest version. In practice, most QR codes contain short URLs well within these limits.

Can a QR code expire?

The QR code itself doesn't expire — it's just a pattern encoding data. But if it encodes a URL that redirects through a third-party service, that service may expire the link. QR codes encoding URLs directly never expire.