How to put a QR code on a poster that people scan

Putting a QR code on a poster is easy. Putting a QR code on a poster that people actually scan — in the street, at a glance, in the rain — takes about six decisions, and most posters get three of them wrong. This is the short version of all six, plus the one that almost nobody makes: deciding, before you print, how you will find out whether it worked.

Make it bigger than feels right

The rule that survives contact with reality is 1:10. A code needs about a tenth of the scanning distance in width. Someone reading an A3 poster at eye height on a pavement is standing roughly a metre away, so the code wants to be around 10 cm across. A shop window scanned from the far side of the pavement is two metres, so 20 cm.

Below about 4 cm you are relying on a good camera, a steady hand and decent light, and you will not get all three at eleven at night. Print one, tape it to a wall, and scan it from where a real person would stand. It takes two minutes and it is the only test that counts.

Leave the quiet zone alone

The blank margin around a code is called the quiet zone and it is part of the code. Scanners use it to find the edges. The specification asks for four module widths — four of those small squares — clear on all four sides.

This is the single most common failure in designed posters, because the quiet zone looks like wasted space to anyone laying out a page. It is not wasted space. Crop it and the code either scans slowly or not at all, and the failure is intermittent, which is worse: it works on your phone in the studio and fails on half the phones in the street.

Contrast, and which way round

Dark modules on a light background, with real contrast between them. Brand colours are fine for the dark part as long as they are genuinely dark — a mid-tone pink on cream will not scan reliably, and neither will anything you would struggle to photocopy.

Inverted codes, light on dark, are the tempting one and the one to avoid. Modern phone cameras usually cope. Older scanners and a lot of in-app scanners do not, and you cannot reprint a wall of posters because someone's phone from 2019 gave up.

Tell people what happens next

A bare code is a request to do something without saying what. Scanning is a small act of trust, and outdoors, from a stranger's poster, that trust is thin. One short line beside the code fixes it:

Scan for tickets — £8 on the door

Not "scan me". Not a bare URL nobody will type. Name the thing on the other side, and name the cost if there is one. The lift from this one line is larger than anything else on this list.

Put it where a hand can reach

Codes belong in the lower third of a poster, on the side a right-handed person's phone naturally goes — which in practice means the lower right. A code at the top of an A1 poster pasted high on a hoarding is a code nobody can hold a phone up to.

If the poster is going in a window at chest height, centre-right is better. If it is going on a lamppost at hip height, higher up the sheet. Where the paper will physically be is part of the design, and it is the part that gets decided last and thought about least.

Decide how you will measure it, before you print

Here is the decision that separates a campaign you can learn from and one you can only guess about.

If every poster carries the same QR code, your analytics will tell you the campaign got 420 scans. That is genuinely useful the first time and useless the second, because it cannot tell you that 380 of them came from the six posters near the station and 40 came from the other ninety-four.

If every poster carries its own code, you find out which walls work. That changes what you print next month: fewer posters, better spots, same budget.

This is what Wildpost does — you upload one design, it generates a unique code for every copy you print, lays them out on print-ready sheets, and when you put a poster up you register its GPS location from your phone. After that, every scan is attributed to a specific wall, pole or window.

The practical difference on a 100-poster run:

The six decisions, in order

1. Size it at a tenth of the scanning distance, then test it on a wall.
2. Keep the quiet zone — four modules clear, all four sides.
3. Dark on light, with contrast you could photocopy.
4. Write one line beside it naming what is on the other side.
5. Place it low and on the reachable side, for where the paper will actually hang.
6. Give every copy its own code, so the scans tell you something you can act on.

The first five make the code scan. The sixth is the one that makes the next print run better than this one.

Related: where to put up posters and reading poster scan data honestly.