QR codes that actually scan: choosing the type, size and error correction

Pick the payload type, not just "a QR code"

A QR code is just text encoded as squares — what the text says determines what phones do with it. Choosing the right payload type makes the difference between one tap and a manual typing exercise:

• URL: the workhorse. Use a full URL including https:// so scanners open it directly rather than treating it as plain text.
• Wi-Fi: encodes the network name, password and security type. Scanning joins the network without anyone dictating a 20-character password — ideal for guest networks and Airbnb routers.
• vCard: a contact card. One scan adds name, phone and email to contacts, which converts far better than asking people to copy details from a screen.
• Email and SMS: pre-fills a message with the address or number, useful for feedback cards and "text us" prompts.
• Plain text: use for anything else — serial numbers, asset IDs, short instructions.

Density is what kills scannability

Every character you encode adds modules — the little squares — and every extra module makes the code harder to scan, especially in print or from an angle. A URL of 30 characters scans effortlessly from a metre away; a 300-character blob of the same URL plus tracking parameters may refuse to scan unless the camera is close and steady. Shorten the URL before encoding, and drop UTM parameters from printed codes (put them on a redirect instead if you need analytics).

Error correction is your safety margin. QR codes store redundant data specifically so they survive damage: at low correction a small scratch kills the code; at high correction the code can lose a whole corner and still scan. The trade-off is density — higher correction means more modules for the same content. A rule of thumb: screen-only codes can use medium correction; anything printed, laminated, on a vehicle or on packaging should use high.

Size, contrast and quiet zone

The classic rule for print: the code's side length should be at least a tenth of the scanning distance — a code meant to scan from 2 metres should be at least 20 cm wide. On screens and paper, keep the quiet zone (the empty margin around the code) intact; wrapping text or a logo tightly around the code is the most common way people break their own QR codes. Dark modules on a light background scan far more reliably than inverted designs, and a decent contrast ratio matters more than any particular colour pair.

Export matters too: PNG is right for screens and documents; SVG is the one to send to a print shop, because it scales to any size without a single blurry module. ToolDock's generator exports both, lets you pick the payload type from a dropdown, adjust error correction and colours, and shows a live preview you can test with any phone camera before you commit it to print.