How QR Codes Work and How to Make a Good One
Web & SEO · October 6, 2026 · 2 min read
A QR code is a square barcode that a phone camera can read. It stores plain text, most often a web address. There is nothing hidden inside it: the black and white squares are just that text, written in a pattern the camera can decode.
What you can put in one
- A web address, so the camera opens the page.
- Plain text, such as a message or a serial number.
- Wi-Fi details, a phone number, an email or a contact card, using standard text formats that phones understand.
Error correction explained
QR codes include spare data so they still scan when part of the code is dirty or covered. There are four levels:
- L recovers about 7 percent damage.
- M recovers about 15 percent.
- Q recovers about 25 percent.
- H recovers about 30 percent, which is useful if you put a logo in the middle.
Higher levels make the code denser, with more small squares. For a code on a screen, M is plenty. For print that might get scuffed, use Q or H.
Rules for a code that scans every time
- Keep strong contrast. Dark squares on a light background work best. Avoid light-on-dark unless you test it.
- Leave a blank border around the code, called the quiet zone, about four squares wide.
- Print it big enough. About 2 cm (under an inch) is a sensible minimum for a code held in the hand.
- Keep the content short. A short web address makes a simpler, easier-to-scan code.
- Always test it with a real phone before you print a thousand copies.
Wi-Fi QR codes
A Wi-Fi code holds your network name, password and security type, so a guest can join by pointing a phone camera at it. The Wi-Fi QR Code Generator makes one. The password is stored in the code itself, so only put it where you would be happy to share the password.
Contact card QR codes
A contact code (a vCard) holds your name, phone, email, company and address, and scanning it offers to save you as a new contact. The vCard QR Code Generator builds it. More details make a denser code, so leave out what you don't need.
Make one now
The QR Code Generator makes PNG and SVG codes. Use SVG for print, since it stays sharp at any size. If the code points to a page you want to track, add campaign tags first with the UTM Link Builder, and check the final address with the URL Parser.
These codes are static. They never expire, but they also can't be changed after printing, so double-check the address before you print.