What can a QR code hold?
A QR code is a square barcode that phone cameras can read. It can contain a website link, plain text, Wi-Fi login details, an email, a phone number or a WhatsApp chat link. Scanning it saves people from typing, which is why QR codes appear on menus, posters, business cards, assignments and shop counters.
Do these QR codes expire?
No. These are static QR codes: the information is stored inside the pattern itself, so they keep working forever and there is no tracking or sign-up. Some websites make “dynamic” codes that point to their own server and stop working when you stop paying. The trade-off is that a static code can't be edited after printing, so double-check the link before you print.
Error correction explained
| Level | Can recover | Use when |
|---|---|---|
| L (low) | about 7% | Screens and clean prints; smallest pattern |
| M (medium) | about 15% | Most uses |
| Q (quartile) | about 25% | Printed items that may get scratched |
| H (high) | about 30% | Outdoor signs or codes with a logo on top |
Tips for codes that always scan
- Keep strong contrast: a dark code on a light background. Light codes on dark backgrounds fail on some phones.
- Leave the white border (the “quiet zone”) around the code.
- Print it big enough: at least 2 × 2 cm, larger for posters read from a distance.
- Use SVG for print so it stays sharp at any size, and PNG for documents and social media.
- Test it with two different phones before printing many copies.