QR codes on hoardings: what actually works
Most hoardings are seen from too far away for a code to be scanned, so be honest about the site. Codes work where people stand or wait: bus shelters, metro stations, mall atriums, petrol pumps, traffic signals and building-side banners at eye level.
Size the code for the distance: about one tenth of the distance people will scan from. Someone scanning from 3 metres needs a code around 30 cm wide. High contrast, a plain white border and no glare from lighting at night matter as much as size.
Pair the code with a short promise readable in two seconds ("Scan for the price list", "Scan to book a free visit"), and keep the landing page to one action. Outdoor viewers are in motion; the page must load fast on 4G and ask for very little.