The QR code on the poster stopped working. Here is why, and how to make one that lasts

The quick answer: make a code that holds the data itself

The poster is up and the code opens an error page. A code that stores your link, text or Wi-Fi details in the squares themselves has nothing to expire, and that is what the QR code generator makes.

1. Open the QR code generator and choose the kind of code: Link, Text, Wi-Fi, Contact, Email, SMS, Phone, Location or Event.
2. Fill in the form. The code updates as you type. For a link, open the address on a phone first, because the code cannot be changed later.
3. Keep the colors dark on light and leave the Quiet zone, the blank border, at 4. Read the notes under the preview.
4. Download a PNG for screens, or an SVG or PDF for print, then scan it with your own phone before you print.

Why a printed code stops working

There are three ways a code dies, and only the last one is about the squares.

1. The redirect belongs to someone else

A dynamic code stores a short web address that belongs to the service that made it, and the service forwards phones to your real page. That lets you change the destination later and count scans. The price: the printed code only works while that service runs and your account stays active. When the account lapses or the service closes, the squares are unchanged but the address they hold leads nowhere. ClipLime does not make dynamic codes.

2. The page behind the code moved

A static code never expires, but it only helps while the page it names exists. A redesigned website or a renamed menu PDF breaks it just the same. Put a short path on a domain you control in the code, such as example.com/menu, and set that page to forward visitors wherever you like. Then you change the forwarding, not the printed code.

3. The code cannot be read

Low contrast, no blank border, a code too small for the distance or too dense, glare, an oversized logo, a blurry screenshot.

Pick the kind of code

Phones recognize the format of the text inside a code and offer the matching action. The exact prompt depends on the phone and scanning app, so scan yours with the devices your audience uses.

A Wi-Fi code guests can actually use

The Wi-Fi QR code generator stores the network name, the password, the security type and whether the network is hidden. Type the name exactly as phones list it, capital letters included, and leave security on WPA / WPA2 / WPA3 unless your router says WEP or the network is open. A work network that asks for a username is not covered.

iPhones recognize Wi-Fi codes in the Camera app and recent Android versions can read them, but most laptops cannot, so put the password in words next to the code.

The password sits in the code as readable text, so anyone who can see or photograph the code can read it. Use your router's guest network for a code on display, with a long random password from the password generator. What you type is not uploaded or saved, and you can check that in the Network tab of your browser's developer tools.

After you change the Wi-Fi password the old code stops working, because it holds the password it was made with. Make a new one.

Size, contrast and the blank border

• Contrast. Dark code on a light background. Many scanners cannot read light on dark, and the tool warns you if you swap them.
• Blank border. The standard sets it at four squares. Without it some scanners cannot tell where the code starts. Do not crop it or let a design run into it.
• Error correction. Levels L, M, Q and H repair about 7%, 15%, 25% and 30% of damage. M suits screens and clean print. Pick Q or H for stickers that will get scuffed, at the cost of a denser code. A logo switches the code to H, so keep it small.

Every character of a link takes space, and a denser code means smaller squares at the same printed width. These are the sizes at medium error correction, with the square size for a code printed 3 cm wide:

So keep the link short. As a rough guide, a phone reads a code from about ten times its width away, so a 3 cm code scans from about 30 cm and a 1 m poster code from about 10 m.

Test it before you print a hundred

1. Print one at the final size on the final material.
2. Scan it from the distance people will stand at, with two different phones, and open the link on mobile data.
3. Read what the code holds with the QR code scanner. Drop in a photo of the proof or use the camera. It names the kind of code and flags short links, plain http and look-alike addresses. Nothing opens until you click.

The scanner reads pictures, not PDF files. If a code arrived inside a PDF, convert the PDF to JPG or take a screenshot first. If codes hang in public places, check them now and then, because a sticker with a different code can be placed over yours. Is that QR code safe shows how to read a code before you trust it.

Printing it, and QR code or barcode

Use the SVG or PDF for print. They are vector files and stay sharp at any size, and the PDF can be sized to the code or centered on a page. If your finished poster is a picture and the printer wants a PDF, save the picture as a PDF. Never print from a screenshot or a JPG copy, because lossy compression can blur the edges of the squares. JPG vs PNG vs WebP vs AVIF explains why. Dark ink on a light, matte surface scans best, since glare on glossy paper hurts any code.

A QR code holds any text. A barcode holds a number or a short piece of text for a scanner at a till or in a warehouse. For your own labels, use the barcode generator. It draws the barcode but does not issue numbers, and products sold in shops usually need numbers licensed from GS1. Make a barcode that scans covers the formats, the check digit and print size. The QR scanner reads QR codes only, so use the barcode scanner for barcodes.