QR codes look like noise but they're a precise encoding system. Understanding a few basics helps you create codes that scan reliably and last as long as you need them to.
What is a QR code
QR stands for Quick Response. It's a two-dimensional barcode that encodes text — a URL, a Wi-Fi password, a phone number — as a grid of black and white squares. Phones can decode it in under a second using the camera, without any app on modern iOS or Android.
The four types you'll actually use
URL. The most common type. Scanning opens a website. The URL is embedded directly in the code, so no server or account is needed.
Wi-Fi. Contains the network name, password and encryption type. Scanning connects the phone directly, without the user typing anything. This is particularly useful for guest networks in offices, cafes and homes.
Text. Displays a message directly on screen when scanned. Useful for instructions, short notes, or identifiers that don't point to a URL.
Phone/SMS. Pre-fills a phone number in the dialler or a number and message in the SMS app. Useful on business cards and flyers.
What is error correction?
QR codes include redundant data that allows the code to be reconstructed even if part of it is damaged. There are four levels:
- L (Low) — 7% recovery. Smallest code, least robust. Fine for pristine on-screen use.
- M (Medium) — 15% recovery. Good default for most uses.
- Q (High) — 25% recovery. Recommended for printed materials that may get scratched or wet.
- H (Highest) — 30% recovery. Use this when you're placing a logo on top of the code, or printing on a surface that will see heavy use.
Higher correction also means a denser, busier-looking code. At small print sizes this can make it harder to scan. For a code smaller than 2 × 2 cm, use M rather than H even if you'd normally go higher.
How big should a printed QR code be?
The minimum reliable scanning size is about 2 × 2 cm at close range. For codes that will be scanned from a distance — on a poster, a shop window, a banner — use this rule of thumb: the code should be at least one-tenth of the maximum scanning distance. A code meant to be scanned from 1 metre away should be at least 10 cm × 10 cm.
Always leave a quiet zone
QR codes require a margin of white space (called the quiet zone) around all four edges. The code itself encodes where this margin should be, but if you butt the code right up against a coloured background or another image element, some scanners will fail to locate it. Leave at least 4 modules (pattern squares) of white space on every side.
Generate a QR code
You can create any of the types above with the free QR code generator. The code is generated in your browser, downloads as a high-resolution PNG, and has no expiry date.