The QR code guide
QR codes are everywhere — on menus, posters, parcels and every Swiss invoice. This guide explains how they work, which types exist, and how to create codes that scan reliably.
What is a QR code?
A QR code (Quick Response code) is a two-dimensional barcode developed in 1994 by Denso Wave, a Japanese subsidiary of Toyota, to track car parts. Unlike a classic barcode, which stores data in one direction, a QR code stores information both horizontally and vertically — up to 4,296 alphanumeric characters or 2,953 bytes.
The three large squares in the corners are finder patterns: they let a camera locate and orient the code from any angle. Smaller alignment patterns compensate for distortion, and timing lines tell the scanner how big each data module is.
How does scanning work?
When you point a camera at a QR code, the software finds the three corner squares, straightens the perspective, and reads the grid of dark and light modules as ones and zeros. Version information and format bits tell it the size of the grid and the error correction in use.
The decoded bits are interpreted according to a content convention: a text starting with “https://” opens the browser, “WIFI:” offers to join a network, “BEGIN:VCARD” creates a contact, “tel:” starts a call. That's all a QR type is — a standardized way to format the encoded text.
Error correction: the readability level
QR codes use Reed-Solomon error correction: redundant data is spread across the code so it stays readable when dirty, scratched or partly covered. This redundancy is exactly what makes center logos possible — the logo simply “damages” an area the redundancy can reconstruct.
Four levels exist. Higher levels tolerate more damage but make the code denser, which can reduce the maximum scanning distance:
| Level | Recoverable damage | Typical use |
|---|---|---|
| L (low) | ~7% | Clean screens, short URLs, maximum simplicity |
| M (medium) | ~15% | Default for most web and print uses |
| Q (high) | ~25% | Outdoor use, small print sizes |
| H (maximum) | ~30% | Codes with a logo, harsh environments |
Static vs. dynamic QR codes
A static QR code encodes your content directly in the image. It works forever, needs no service behind it, and nobody can track who scans it. QRGen creates static codes exclusively — that's why they never expire and why we can run without storing anything.
A dynamic QR code encodes a short redirect URL owned by a provider. The destination can be changed later and scans can be counted — but the code stops working if the provider shuts down or puts it behind a paywall, and every scan is logged. For most use cases, a static code is the safer, more private choice.
Which QR code type for which purpose?
The content types on QRGen cover the everyday cases:
Website (URL)
The classic: opens a web page. Keep URLs short — shorter text means a coarser, easier-to-scan code.
Wi-Fi
Guests join your network without typing a password. Popular in cafés, offices and holiday flats.
vCard
A complete contact card — name, company, phone, e-mail, address — saved to the phone in one scan. Ideal for business cards.
E-mail, phone & SMS
Pre-filled messages or one-tap calls. Great for support hotlines and feedback.
Location
GPS coordinates that open in the maps app — for event flyers and signposting.
Bitcoin
A payment request with address and amount in the BIP-21 format most wallets understand.
The Swiss QR-bill (QR-Rechnung)
Since 30 September 2022, the QR-bill has fully replaced the orange and red payment slips in Switzerland. Every invoice now carries a payment part with a Swiss QR Code — recognizable by the Swiss cross in the center — containing the account (QR-IBAN), amount, currency, reference number and addresses in a strictly standardized structure defined by SIX, the operator of the Swiss financial infrastructure.
Because banks validate this structure, a QR-bill should be generated with certified invoicing software or your bank's tools — a hand-made code with the wrong reference type will be rejected at payment. QRGen deliberately focuses on general-purpose QR codes; for QR-bills, use the official channels. Our vCard, website and Wi-Fi codes, on the other hand, follow open standards and work with any scanner worldwide.
Best practices for reliable scanning
Contrast first: Dark code on light background. Inverted or low-contrast codes fail on many scanners.
Respect the quiet zone: Keep an empty margin of at least 4 modules around the code.
Size for the distance: Rule of thumb: scanning distance ÷ 10 = minimum code width. A poster scanned from 2 m needs a code at least 20 cm wide.
Print in vector: Use the SVG export for anything printed. Pixelated codes scan poorly.
Test before publishing: Scan with iOS and Android, in bad light, at an angle. Then print.