QR Codes: complete guide, creative uses and security
QR codes are everywhere: restaurant menus, business cards, labels, payments, posters. They're a simple but incredibly useful technology, when used well. This guide covers how they work, when to use them, and what risks to avoid.
What is a QR code and how it works
A QR Code (Quick Response Code) is a two-dimensional barcode invented by Denso Wave in 1994 to track automotive components. Compared to linear barcodes, it can hold much more data (up to ~7000 numeric characters) and is read in any orientation thanks to the three squares in the corners.
When you scan a QR with your smartphone camera, the phone decodes the content and performs the corresponding action: opens a URL, shows text, composes an email, calls a number, connects to WiFi.
Effective use cases
- Digital menus: in restaurants, avoids paper menus and allows instant updates.
- Guest WiFi: generate a QR with WiFi credentials, guests scan it and connect without typing passwords.
- Business cards: a vCard in the QR, scanning it saves the contact directly to address book.
- Payments: PayPal, crypto wallets use QR to receive payments.
- Inventory labels: QR on boxes or equipment pointing to technical sheets.
When NOT to use a QR code
QR codes aren't always the right solution. Avoid them when:
- The content must be readable without a smartphone (e.g. safety instructions).
- The target is an elderly audience unfamiliar with smartphones.
- The QR is too small or exposed to reflections (shop windows): hard to scan.
- You want to track clicks (better a normal UTM link with analytics).
Security: QR risks
A QR can point to any URL, including malicious ones. "Quishing" (QR + phishing) attacks paste fake QRs over real ones (parking meters, EV chargers). To protect yourself: most phones show the URL before opening it — always read it. Be wary of QRs asking for credentials or sensitive data.
How to create a good QR code
For a readable and robust QR:
- Use short URLs: less dense QRs = easier to scan.
- At least 200×200 pixels for screen, 500+ for print.
- Don't shrink below 2cm in small prints.
- Always test with multiple devices before printing thousands of copies.
- High contrast: black on white is the most reliable.