How QR codes carry data
A QR code is not a link to a database — it is the data itself, encoded as a grid of black and white modules. When a phone scans a code containing a website address, the address was physically printed in that pattern. Nothing is looked up, and no server is involved.
That has a practical consequence worth knowing: a code generated here never expires and cannot be switched off, because there is nothing to switch off. Many commercial QR services instead encode a short link pointing at their own domain, which lets them track scans and change the destination later — but also means your code stops working if they shut down or start charging.
Choosing an error correction level
QR codes store redundant data so they still scan when partly damaged or obscured. Higher correction means more redundancy, but also a denser grid for the same content.
- Low (7%) — clean digital use, screens and PDFs. Smallest, densest-free pattern.
- Medium (15%) — the sensible default for most printing.
- Quartile (25%) — printed material that may get handled, folded or scuffed.
- High (30%) — required if you plan to place a logo over the centre, or for labels exposed to wear.
Making a code that actually scans
Three things break QR codes more often than anything else. First, low contrast: a light foreground on a light background may look elegant on screen but defeats most scanners. Keep the foreground substantially darker than the background, and avoid inverting them.
Second, size. A rough rule is that the printed code should be at least one tenth of the distance it will be scanned from — a code read at one metre wants to be around ten centimetres across. Third, quiet space: leave a clear margin of at least four modules around the code. Placing it flush against text or a border is a common cause of failed scans.
What each code type does
The WiFi type encodes network credentials in a format Android and iOS both recognise, so a guest can join without typing a password. The Contact type produces a vCard, which phones offer to save directly into the address book. Email opens a pre-composed message. All of them are plain text under the hood — you can see exactly what is encoded, and nothing is hidden behind a redirect.
Frequently asked questions
Do these codes expire?
No. The data is inside the code itself, so it works for as long as the destination it points to exists. There is no account, subscription or service that could stop it.
Can I use these commercially?
Yes. Codes you generate here are yours to print on packaging, menus, business cards or signage, with no attribution required.
Is my WiFi password sent anywhere?
No. The code is drawn in your browser from what you type. Close the tab and nothing remains — but do remember that anyone who scans the printed code gets the password.
PNG or SVG — which should I download?
SVG for anything going to print, since it scales to any size without losing sharpness. PNG for screens, email signatures and social posts.