Wedding QR code not scanning? Start here

You print the cards, you hold a phone over one, and nothing happens. This is alarming three days before a wedding and it is almost never the code itself. A QR code is a fixed pattern, so if it was generated correctly it is still correct on paper, and the fault is in something around it.

Work through these in order. They are ranked by how often each one turns out to be the cause, not by how technical they sound.

A wedding QR code not scanning usually means the print

Check the size first. A code needs enough physical area for the camera to resolve the individual squares, and how much depends on how far away the phone is held. On a card somebody picks up, about two centimetres square is usually workable and three is comfortable. On a sign people read from a metre away, it needs to be far larger than looks necessary, because the phone is resolving the same squares from five times the distance.

Then check that nothing scaled it. Printing a card to fit a page is the most common way a good design becomes an unreliable one, because a print dialogue set to fit shrinks everything by a few percent and the code goes with it. Print at exact size, every time, and if a sheet does not fit at exact size then the sheet is wrong rather than the card.

Finally, check the contrast and the direction. Dark squares on a light background is what every scanner expects. A light code on a dark card can work and frequently does not, and the same is true of a code printed in a colour rather than something close to black. Gold on cream looks lovely and is the single most common way a wedding card ends up unscannable.

The empty margin around it is part of the code

This is the one that catches designers, because the margin looks like wasted space and it is not. The standard requires a clear border around the pattern equal to four of its own squares, and a scanner uses that emptiness to find where the code starts and stops.

Crop it tight, put a border right up against it, or run a background pattern underneath it, and you get a code that scans in good light on a new phone and fails on an older one held at an angle. It will pass every test you run and fail for a quarter of your guests, which is the worst possible outcome because you will never hear about it.

The same goes for putting anything on top of the code. A monogram or a small logo in the middle is a popular look and it eats into the redundancy that lets a scanner cope with a fingerprint or a fold. If you want the card to carry your names, put them above or below the code rather than inside it. Where to put the card so guests actually use it covers the placement side of the same problem.

It scans, but the page does not open

This is a completely different fault and the fix is nothing to do with the card. If the phone shows a notification with a link, the code is fine. Everything after that is connectivity.

Venue wifi is the usual culprit, and it fails in a specific way: the phone joins the network, the network wants you to accept terms on a page that never appears, and every request afterwards goes nowhere. Guests read that as the code being broken. Why venue wifi behaves like this is worth reading before the day, because the fix is usually to tell guests to turn wifi off and use their own data. If nobody at a table can open the page but the code shows everyone a link, stop checking the card and put the link in the group chat instead, and let people carry on from there.

Testing it properly, and what to do on the night

Test on a phone that is not yours, and preferably an old one. Your phone has scanned this code before, has the page cached, and has a better camera than half the room. A borrowed phone in poor light, held the way a guest holds it, tells you something your own phone cannot.

Test under the actual lighting too, if you can get into the venue. Candles and warm downlights are dim and directional, and a laminated or glossy card in that light reflects the source straight back into the camera. Matte stock scans in conditions that glossy stock will not.

On the night, have a fallback that needs no card. Somebody says the link out loud during the speeches, or it goes into whatever group chat already exists, or a phone with the page open gets passed to the table that is struggling. One person getting in is usually enough, because they show the person next to them. Setting the gallery up in the first place walks through printing the cards and checking them before you commit to a hundred.