What each type does
- Link opens a web page. If you leave out https://, it is added for you, so logicox.com works.
- Text shows the text on the phone. Urdu, Hindi and emoji are encoded as UTF-8, which modern phone cameras read correctly.
- Wi-Fi lets guests join your network without typing the password. Most iPhone and Android cameras offer to connect straight away.
- Phone opens the dialler with the number filled in.
- WhatsApp opens a chat with your number and, if you add one, a ready-made message. Use the full number with country code.
These are static QR codes: the information sits in the pattern itself, so they never expire and need no account. The trade-off is that you cannot change where a printed code points; to change it, make a new one.
Error correction levels
QR codes store extra data so they still scan when part of the code is dirty, scratched or covered. Higher levels survive more damage but need more squares, so the code gets denser.
| Level | Can recover about | Use it for |
|---|---|---|
| Low (L) | 7% | Screens and short links |
| Medium (M) | 15% | Most uses |
| Quartile (Q) | 25% | Printed items that get handled |
| High (H) | 30% | Outdoor signs, or a logo placed over the centre |
Tips for codes that scan
- Keep a dark code on a light background. Light-on-dark codes fail on many phones, and the tool warns you about weak contrast.
- Leave the white border around the code; scanners need it to find the edges.
- Print it at least 2 cm wide, and bigger if people will scan from a distance. A good rule is one tenth of the scanning distance.
- Shorter content makes a simpler code that scans faster, so use short links where you can.
- Always test a printed code with two or three different phones before you print a large batch.