QR Code Generator

QR Codes — How They Work, Types, and Best Practices

QR codes (Quick Response codes) are two-dimensional matrix barcodes invented in 1994 by Masahiro Hara at Denso Wave for tracking automotive parts in Japanese factories. Today they are scanned billions of times daily — on restaurant menus, retail packaging, event tickets, payment systems and public transport. The pandemic-era shift to contactless interaction dramatically accelerated adoption in hospitality and retail, and that usage has largely persisted. Knowing how to generate effective QR codes is now a practical skill for anyone in marketing, design or small business.

How QR codes store data

A QR code stores data as a pattern of dark and light modules (squares) on a grid. Capacity depends on version (which sets grid size) and error correction level. Version 1 is 21×21 modules; each increment adds 4 modules per side up to Version 40 at 177×177 modules. A Version 40 code at error correction L can store up to 7,089 numeric characters, 4,296 alphanumeric characters or 2,953 binary bytes. Data uses Reed-Solomon error correction, adding redundant data so a code can be read even if part is missing — which is why logo overlays are technically possible without destroying scannability.

Error correction and why logo overlays work

The four error correction levels — L (7%), M (15%), Q (25%) and H (30%) — indicate the maximum percentage of modules that can be obscured or damaged while full decoding is still possible. Higher levels produce denser codes but are more robust. Level H is required for logo overlays: at 30% redundancy, a logo covering up to 25–28% of the code area leaves enough intact data for reliable decoding. Always test a logo-overlaid QR code on multiple devices and scanning apps before deploying, since different implementations have different tolerance thresholds in practice.

WiFi QR codes — the most practically useful type

WiFi QR codes encode credentials in the format WIFI:T:WPA;S:networkname;P:password;; and are natively supported on iOS 11 and Android 10 and above. When scanned, the phone displays a "Join network?" prompt requiring a single tap. Generate one, print it at A5 or larger, and display it prominently at your venue. The SSID must exactly match the router's SSID including capitalisation — special characters like semicolons, commas and backslashes in the network name or password must be escaped with a backslash. This generator handles escaping automatically.

vCard QR codes for contact sharing

A vCard QR code stores contact information in the VCF standard that iOS Contacts, Google Contacts and Outlook import directly. When scanned, the phone offers to add the contact with a single tap — no typing. Fields include name, phone, email, organisation, title and website URL. At conferences and networking events, a QR code on a name badge eliminates the physical business card exchange and the transcription errors that go with it. The vCard 3.0 format used here is compatible with essentially every contacts application on every platform.

SVG versus PNG — which format for which use

PNG is a raster image with a fixed pixel resolution. It looks sharp on screen and at small print sizes but blurs when scaled beyond the generated size. SVG is a vector format that describes shapes mathematically, rendering at perfect sharpness at any physical size from a 2cm business card square to a 10 metre hoarding. Professional print workflows in InDesign, Illustrator and Canva Pro prefer SVG or PDF input. For digital use at a known fixed size — a webpage, email signature or social post — PNG is simpler and universally supported. For any print application where the final size is uncertain, always download SVG.

Best practices for reliable real-world scanning

Minimum physical size for reliable scanning at arm's length is 2.5 cm (1 inch) square. A rough guide for larger codes is: minimum size in centimetres equals viewing distance in metres multiplied by 1.5. Always include a quiet zone — a clear border of at least 4 module widths — so scanners can locate the code boundary. Maintain high contrast: mid-grey on white or similar-tone pairs fail on many scanners. For outdoor, worn or printed QR codes use error correction Q or H. Print on matt rather than glossy where possible — reflective surfaces cause glare that interferes with phone cameras. Test the final code on at least two different devices before committing to a print run.

Frequently asked questions