Why one code isn't enough
The most common mistake is printing one QR code on everything. It works, but all you learn is a total. Give each placement its own code and you'll see that the slide at the meetup brought 18 people and the 200 flyers brought 3. A code costs nothing extra, and this is how you learn what to print next time.
How big should an event QR code be?
The common guideline is a 10:1 ratio: the code should be about a tenth of the distance it's scanned from. It's a rule of thumb, not a standard. Phone cameras, lighting and how much data the code holds all change the result, so round up.
| Where | Scanned from | Code width |
|---|---|---|
| Badge or table card | 30 cm (1 ft) | 3 cm (1.2 in), at least |
| Flyer or A5 handout | 50 cm (1.6 ft) | 5 cm (2 in) |
| Poster on a wall | 1.5 m (5 ft) | 15 cm (6 in) |
| Pull-up banner | 3 m (10 ft) | 30 cm (12 in) |
| Back of a meeting room slide | 6 m (20 ft) | 60 cm (24 in) as shown on screen |
Sources disagree about the smallest usable size, from around 1 cm to 2.5 cm. The QR standard itself sets proportions rather than a physical minimum. For anything people scan on the move, stay well above that.
Leave a clear margin
Denso Wave, which invented the QR code, states that a code needs a clear margin four modules wide on every side, where a module is one of the small squares. Nothing printed goes there. This is the rule designers break most often, usually by placing a code tight against a photograph or a border. If a code won't scan, check the margin first.
Keep the link short
A QR code gets denser as it holds more characters. A long address with UTM tags creates a tight pattern with tiny squares, which is harder to scan at a distance and less tolerant of bad printing. Put a short link in the code instead, and let it forward to the full address.
A short link gives you three more things: you can count scans, you can change where it goes after printing, and the source is built into the address, so it can't get stripped.
Where to put them
- The last slide of a talk, and the first one, while people are waiting. Leave it on screen for longer than feels necessary, and say out loud what it's for.
- Posters, at eye level, somewhere people stand still: by a lift, a coffee queue, a door.
- Badges and table cards, where people can bring their phones close.
- Printed programmes, with one code per session rather than one for the whole event.
- Screens between sessions at a conference, for the next event.
Give the code a sentence. A bare QR code asks people to scan on trust. "Scan to get a place: Thursday, 6pm, 40 seats" gives them a reason.
What should a scan open?
Whoever scans a code is holding a phone and has about ten seconds of patience. A long form is the worst place to send them. Two options work well:
- A short, phone-friendly event page with a one-tap way to register.
- A ready-written email. The scan opens the person's own mail app with everything filled in, and they press send. There's nothing to type, and they've proven the address by sending from it. This works well in a room. See QR sign-up for meetups.
Which file format to use
| Format | Use it for |
|---|---|
| SVG | Design tools and the web. Scales to any size. |
| PDF or EPS | Print shops. Vector, so a banner stays sharp. |
| PNG | Slides, documents and social images. Use a large one. |
Never enlarge a small PNG for print: blurred edges are a common reason for codes that fail.
Can you put a logo in a QR code?
Yes. QR codes carry error correction, so part of the pattern can be covered and the code still reads. Denso Wave lists four levels, from L to H, where M restores about 15% of the data and Q about 25%. For a logo, use the highest level, H, keep the logo small and central, and test it. Colours are fine as long as the code stays dark on a light background with strong contrast. Inverted codes are unreliable on some phones.
A check before printing
- Print a proof at the real size.
- Scan it at the real distance, from two or three different phones, one of them older.
- Scan it in the real light, too. A dim bar is harder than an office.
- Follow it through to the end and complete a registration.
- Confirm the scan and the registration both appear under the right source.
After the event
Printed codes outlive their events. A poster stays up, a programme sits in a bag, and months later somebody scans a code that goes nowhere. If your code points at a short link, you can send those scans on to your next event or your series page, so old print keeps bringing people.
Doing this in Programmable Talk
Every way in gets a QR code on a short link that counts scans, without keeping IP addresses or counting link previews. Codes open your page or a ready-written registration email. They come as SVG, PNG, PDF and EPS, or all at once as a ZIP with a codes.csv, and with your logo in the middle at error correction level H if you want it. After the event, each code forwards to your next event or series.