Two QRs on one poster, which to scan

The mistake that made this note

Last week we had a small board taped on the shop glass. It looked clean on the laptop. The heading was straight, the price was big, and the QR had plenty of confidence. Then a customer scanned it and the wrong thing happened. That small pause at the counter is enough. People stop trusting the board.

The title of this note is “Two QRs on one poster, which to scan”. It sounds narrow because the actual problem is narrow. A QR is not clever. It stores QR file, white margin, and final print size. If that input is wrong, the square repeats the mistake very neatly, maybe two hundred times.

I used to check only whether the QR looked like a QR. That check is useless. Random blocks can look fine while the destination is old, the number has one extra digit, or the print has lost its white edge. Now the check is about what opens after the scan.

Camera grabs the nearer square. Label both or print one. That is the short version. The longer version below is what I wish the printer had told me before taking the advance.

What the code really contains

A QR needs dark modules, a pale background, and a clean border around all four sides. Download the PNG instead of photographing the monitor. Start with a larger file when the board will be seen from a distance. A sharp proof on paper tells more than a zoomed preview.

There is no account on QROnDesk and no saved history. The work happens in the browser tab. The site makes a string and asks the browser QR library to draw it. Downloading gives you a PNG. Copying gives you the same underlying text where the tool supports it.

That also means the tool cannot guess intent. If a shop has two similar profiles, two old phone numbers, or two map pins with the same name, the page cannot choose for you. It is an encoder, not a directory.

Write the final value in a small notebook or order message as well. When the print arrives, compare the opened destination with that written value. Do not compare with memory. Memory says the last digits are probably right. Paper says what they actually are.

Make it on this site

Open the tool used for this job. Read the labels once before typing. Put in the final information, not sample text that you plan to replace later. Sample text has a bad habit of reaching the printer.

If the tool shows a QR preview, wait for it to appear and use Download PNG. If it shows a link, use the copy button and paste the result into a fresh browser tab or the correct app. Do not manually rewrite encoded spaces or punctuation. The odd-looking percent signs in a URL often represent normal message spaces.

Keep the downloaded file with a useful name. “final.png” is not useful when there are six finals in Downloads. Add the shop, event, or month to the filename after saving it. The QR contents do not change when the filename changes.

Use a second phone for the proof scan. The phone that made the file can hide mistakes because the copied link is still in its recent history.

No login is needed. Do not give this page a bank password, UPI PIN, WhatsApp OTP, or email password. There is no box for any of those, and a real encoder does not need them.

A proof scan is not optional

First scan the large preview on the screen. This catches a bad input quickly. Next download the PNG and open that exact file. Scan the file from another screen. Finally print one proof at the intended physical size and scan the paper.

These are three different checks. Screen success proves the payload can be read. File success proves you saved the right image. Paper success proves the printer, size, colour, and surface still let a camera read it.

Stand where the customer will stand. If the QR is behind glass, test through that glass. If it is under a tube light, test with the reflection. If it is on a food counter, put the proof flat where the final board will sit. A perfect scan from five centimetres is not useful when customers are one metre away.

Try an ordinary mid-range phone, not only the newest phone in the shop. Clean the camera once, but do not spend ten minutes forcing a scan. A customer will give it two seconds. If it does not open quickly, make the square bigger and increase the contrast.

After it opens, read the destination. For a number, read every digit. For a map, zoom out and check the city. For a profile, check the handle. For text, check the date and spelling. For a payment draft, read the receiver shown by the UPI app and stop before confirming if anything feels wrong.

Print size and the quiet white edge

The white border around a QR is called a quiet zone. The name is good: no price text, border art, logo, or dark photograph should shout inside that space. Keep it plain. A designer may want to make the square touch a coloured frame. Ask them to leave breathing room.

A visiting card needs a square large enough for its data and print quality. A wall poster needs more because the scan distance is longer. The QR size helper offers 200, 400, and 800 pixel previews. Pixels do not directly promise centimetres, but the larger download gives the printer more useful detail.

Do not stretch a tiny screenshot until it fills a flex. The blocks become soft, especially after a messaging app compresses the image. Send the original PNG as a document when possible. If the print shop asks for a PDF layout, place the original PNG in the layout; do not paste a chat preview.

Black on white remains the safest choice. Dark green on white can work, but pale modules on a pale background are trouble. Glossy lamination can add glare. Matte paper is often easier at a counter. None of this is fashionable advice. It is just what the camera can separate.

Common ways this job goes wrong

The first error is using an old value from chat history. Someone sends a new number, but the designer copies the earlier message. Put the final value in one clearly marked message and delete no context until the proof is approved.

The second error is adding decoration inside the QR. A logo in the middle removes modules. Error correction may rescue a small obstruction, but there is no reason to gamble on a shop board. QROnDesk gives a plain code. Put brand text beside it.

The third error is changing the destination after printing. A plain QR is static. It keeps the same text forever. If a phone number changes, make and print a new code. If an offer date changes inside a text QR, make and print a new code. The square does not update itself.

The fourth error is testing only with the person who made it. Ask one other person to scan without explaining what should happen. Watch where they point the camera and what they think the opened page means. Their confusion is part of the test.

The fifth error is placing two unlabeled QRs close together. A camera may choose either one. If WiFi and payment must share a board, give each a clear title and enough space. Better still, use separate cards when the counter has room.

A small checklist before the printer starts

1. Open the exact QR file, white margin, and final print size directly and confirm it is current.
2. Generate again from the final value, not an old screenshot.
3. Download the PNG and keep the original file.
4. Scan the screen preview on a second phone.
5. Scan the saved PNG and read what opens.
6. Print one sample at the real size.
7. Scan from normal customer distance and through any glass.
8. Check spelling, number, city, profile, or receiver one more time.
9. Approve the bulk run only after the proof passes.

I keep this list short enough to use. A long policy pinned behind the desk gets ignored. Nine checks look like work, but they take less time than calling the printer about two hundred wrong flyers.

What to put beside the square

Give the QR a plain instruction: “Scan to chat”, “Scan for WiFi”, “Scan for directions”, or “Scan to view”. The label should match what opens. Do not write “Pay here” beside a map code or leave an old heading above a replaced sticker.

Print a readable fallback when it is safe. A shop phone number can sit below a chat QR. A WiFi password may be kept behind the counter instead of printed. A map board can include the area name. A payment board should let the customer compare the receiver name in their app.

Do not claim that a scan is secure merely because it is a QR. A QR can hold a good link or a bad link. The customer still needs a destination they recognise. Your job is to make that destination obvious before they tap.

When to make a fresh QR

Make a new file whenever the encoded text changes. Make one when the shop number moves to a new SIM. Make one when a profile handle changes. Make one when a map pin was corrected. Make one when an event note has a new gate or date.

Also make a new file if the old image has been cropped, filtered, compressed, or covered by a sticker. Generating again takes under a minute and gives you a clean original. Trying to repair missing blocks in a photo takes longer and may still fail.

Keep the approved proof for comparison. Write the date on the back. At the start of a new season, scan every code still hanging in the shop. Sun fades ink. Tape gathers dust. Staff replace phones. The code may be technically readable while its destination is no longer useful.

The simple rule

The sequence is input, generate, download, scan, print one, scan again, then approve. Do not move printing ahead of scanning because the press is waiting. The press can wait three minutes.

For this exact job, start with the related QROnDesk tool. It runs in the browser and makes a plain result without a fake brand mark. Save the PNG if there is a QR. Copy and test the link if there is a link.

One final warning for any payment-related material: QROnDesk is not WhatsApp, NPCI, or a bank. It cannot confirm who owns a UPI ID. This QR is only as correct as the UPI ID you typed. Test with 1 rupee.

The square is the easy part. The checking is the useful part. Do both before the stack reaches your counter.