How to create a QR code that scans every time: size, contrast and error correction

A QR code is just a picture that encodes text, usually a link. Most scanning failures come from a handful of avoidable mistakes.

Steps

1. Decide what to encode: a web address, plain text or contact details.
2. Paste it into the generator and download the image.
3. Print or place it, then test it with at least two phones.

Rules that prevent failed scans

• Keep the quiet zone. Leave a blank border around the code, at least four modules wide, with nothing printed in it.
• Use strong contrast. Dark code on a light background is safest. Inverted or low-contrast colours scan unreliably.
• Print it large enough. As a rule of thumb, allow about 2 cm for a code scanned from close range, and more for posters scanned from a distance.
• Keep the data short. A shorter link makes a simpler code with bigger squares.

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Error correction levels

QR codes carry redundant data so a damaged or partly covered code can still scan. The four levels in the QR standard can recover roughly this share of the data:

Higher levels survive logos and scratches but make the code denser, so use the lowest level that fits your situation.

Static means permanent

A code made by this kind of generator encodes your link directly, so it never expires and nothing about your scans is tracked. The trade-off is that you cannot change the destination later, so check the link before you print thousands of copies.

Create yours in the generator below. It runs in your browser with no sign-up.

What you can put in a QR code

• Website link: the most common use. Use the final, https address.
• Plain text: a message, coupon code or serial number.
• Wi-Fi login: encoded as WIFI:T:WPA;S:NetworkName;P:Password;; so guests can join by scanning.
• Email, phone number or SMS: opens the app with the details filled in.
• Contact card (vCard): lets people save your details in one tap.
• Location: a geo coordinate or a map link.

How much data fits?

QR codes come in 40 versions, from 21 × 21 modules (squares) up to 177 × 177. The largest can hold about 7,089 digits or 4,296 letters and digits. In practice, shorter is better: a 25-character link produces a small code with big squares that scans quickly, even on a cheap camera. If your link is long, use a short redirect link you control.

How big should a printed QR code be?

A common rule is a scanning distance to code width ratio of about 10 to 1. A code on a poster read from 2 metres should be about 20 cm wide. A business card code is usually 2 cm, which is fine for close scanning with short data. Always test at the real size and distance.

File formats: PNG, SVG and PDF

• PNG is fine for screens and small prints. Export large enough that it is not blurry.
• SVG or PDF are vector formats that scale to any size without blurring, which suits posters, packaging and signs.

Do not stretch the image, and do not compress it as a JPG, because artefacts around the squares can break scanning.

Colours and logos

Scanners need contrast between the dark and light parts, and most expect dark squares on a light background. You can use brand colours if the contrast is strong. A logo in the centre works only with higher error correction, because it covers part of the data. Test before you print.

Where to place a QR code

• Use a flat surface. Curved bottles and creased paper distort the squares.
• Avoid glossy finishes that reflect light.
• Leave the quiet zone clear around the code.
• Add a short line telling people what they get, such as "Scan for the menu".

Static or dynamic codes?

A static code stores your data in the pattern itself. It never expires and needs no account, but you cannot change it. A dynamic code points to a redirect service, so the destination can be edited and scans can be counted. The trade-off is that the code stops working if the service stops or you stop paying. For a permanent printed item, a static code to a page you control is often safest.

Stay safe when scanning

Criminals sometimes paste fake QR stickers over real ones, or send QR codes in emails to lead people to fake sites. Check the web address your phone shows before you open it. Be cautious if a code asks for a password or payment, and do not scan codes from unknown sources.

Testing checklist

1. Scan with at least two phones, one old and one new.
2. Test in poor light and from the expected distance.
3. Open the link and confirm it is the final page.
4. Print one proof before you print a thousand.

Troubleshooting: common problems and fixes

• The code does not scan. Increase the size, improve contrast, shorten the data and keep the quiet zone clear.
• It scans on some phones only. Test on multiple phones. Very dense codes need a better camera, so shorten the link.
• The logo breaks the code. Use higher error correction and a smaller logo, and test again.
• Print looks blurry. Export at a higher resolution or use a vector format.
• The link needs to change. A static code cannot be edited. Use a redirect link you control or print a new code.

Is the QR generator private?

The generator creates the code in your browser. Your link or text is not uploaded or tracked, and the code never expires. Always test before printing, and only scan codes from sources you trust, since fake codes are used for scams.

More free Zyphub tools you may need

• QR Code Generator: QR codes for links and text.
• Password Generator: Strong random passwords.
• Image Converter: JPG, PNG and WebP.

General information only, not tax, legal or financial advice. Rates change, so check the official source.