Mobile-First

Mobile-first is an approach to designing websites and applications in which the display / operation on smartphones is designed first and then extended for tablets and PCs. Since Google introduced mobile-first indexing in 2018, it has also become a standard design method from the standpoint of SEO.

For the link destinations of QR codes, mobile-first is not an option but a precondition. The devices that scan QR codes are almost 100% smartphones. Cases of scanning with a PC are limited to special situations that use a webcam. In other words, QR code landing pages should be designed on the assumption that they "can only be viewed on mobile".

On a mobile-first QR code landing page, the points to emphasize are placing the CTA above the fold (prompting action without scrolling) and making tap targets large enough (at least 44 by 44 points). Keeping form input fields to a minimum (input on a smartphone is more of a burden than on a PC) and getting the page to load within 3 seconds (assuming a mobile connection) also matter.