# QR codes for webinar signup > For slide codes, size for the room — the ten-to-one rule means a back row 10 m away needs a code about a metre wide, a third of a typical projection. Audiences photograph slides and scan later, so leave the code up through Q&A and pair it with a short URL and a calendar step. Source: https://useqr.app/docs/marketing/qr-codes-for-webinar-signup · Last reviewed 2026-08-21 · UseQR is free forever, MIT licensed, no signup. --- ## Two moments, two codes Webinar registration has exactly two moments where a QR code earns its place: 1. **Promotion** — flyers, posters, conference handouts, booth panels pointing at the registration page. Ordinary print rules apply: 3 cm at arm's length, [10–30 cm on panels](/docs/marketing/qr-codes-at-trade-shows), a stated benefit beside the code. 2. **The closing slide of a live talk** — the highest-intent audience you will ever face, already convinced by forty minutes of you, needing only a frictionless way to get the next thing. This is the moment worth engineering, and it has its own physics. Tag them separately — `utm_content=flyer` versus `utm_content=talk-slide` — so you learn which moment fills the webinar; the [UTM how-to](/docs/how-to/how-to-add-utm-parameters-to-a-qr-code) has conventions. ## The closing-slide physics A projected slide is a screen read from much further than a poster, and the 10:1 distance rule is unforgiving about it. A typical projection is 2.5–3 m wide; a mid-sized room seats people **10–15 m** from it. The back row therefore needs a code **1–1.5 m wide on the projection — a third to half the slide**. The discreet corner code that looks tasteful in the deck is unscannable beyond the front rows; the same arithmetic governs [codes on TV screens](/docs/print/qr-code-size-on-a-tv-screen). So design the slide around the code: the code enormous, one line of benefit ("Seats for the deep-dive — 30 seconds to register"), and a short typeable URL beneath it. Nothing else. Every additional element shrinks the one thing the slide exists to do. Two behaviours work in your favour: - **Audiences photograph slides.** Phones can [scan a code from a photo](/docs/scanning/how-to-scan-a-qr-code-from-a-photo) later — and in a photo of the whole room, your code is a small region of the frame, which is precisely why oversizing matters. Big codes survive being photographed; small ones become smudges. - **A slide has no time limit.** Unlike [video](/docs/design/minimum-on-screen-duration-for-a-qr-code), you control the projector — leave the registration slide up through the entire Q&A. Minutes of passive exposure beat any ten-second end card ever aired. ## From signup to attendance: the calendar step Webinar economics die between registration and the live date — people sign up sincerely and forget completely. The single highest-leverage fix is getting the event into the registrant's calendar at the moment of signup: - Have the confirmation page offer the event as a calendar entry — a [calendar QR code](/calendar-qr-code) on the thank-you screen works when the signup happened on a laptop and the phone should hold the reminder; the [calendar generator](/calendar) builds the event payload, which the phone saves **offline, no server involved**. - Send the standard confirmation email with an attached invite as well; the two channels are complementary, not redundant. A calendar entry is a reminder you did not have to earn twice. Reminder emails still help, but they compete with the inbox; the calendar alarm does not. ## Before the talk Load your own deck, walk to the actual back row, and scan the slide. If it fails from there, the code is too small — fix it before the audience proves it for you. And decode the artwork with the [validator](/validate) whenever the deck has been through a designer: recolouring and compression have quietly killed more slide codes than projectors ever did. ## FAQ ### How big should a QR code be on a presentation slide? Size for the back row: at 10–15 m from a 2.5–3 m projection, the 10:1 rule demands a code 1–1.5 m wide on screen — a third to half of the slide. Make the code the slide's main element, not a corner ornament. ### Should I leave the QR code up during Q&A? Yes — it is your biggest advantage over video. A slide has no duration limit, so minutes of passive exposure let everyone scan at leisure, including people photographing the screen to scan later from the photo. ### How do I stop webinar registrants forgetting to attend? Put the event in their calendar at signup: a calendar-file link or QR on the confirmation page, plus an invite attached to the confirmation email. A calendar alarm fires regardless of inbox noise, which reminder emails cannot promise. ### What should the webinar registration form ask for? As little as possible — email, perhaps name. The scanner is standing in a conference room or reading a flyer; every extra field costs registrations, and everything else can be collected inside the confirmation flow. ## Try it - https://useqr.app/url - https://useqr.app/calendar - https://useqr.app/validate