Fallback

A fallback is an alternative means that is switched to automatically when the primary means is unavailable. In web development, it refers to a design that substitutes basic functionality when features intended for the latest browsers do not work in older browsers.

In operating QR codes, designing fallbacks is important in several situations. The first is an alternative means when reading fails. In case the QR code cannot be read because of dirt or damage, writing a short URL as text below the QR code lets users access it by typing it in manually. In guidance aimed at older people, listing a phone number alongside the QR code is also an effective fallback.

The second is an alternative page when a redirect fails. When the redirect destination of a dynamic QR code is temporarily down, this design displays an alternative page such as "We are currently undergoing maintenance. Please contact us here" instead of an error page.

The third is a fallback when the app is not installed. When a QR code tries to open an app's deep link but the user has not installed the app, a common design is to fall back to the installation page on the App Store or Google Play. What needs to be distinguished here is this: simply sending the user to the store and stopping there is merely a fallback. It is only called a deferred deep link when it goes as far as restoring the original destination (a specific screen within the app) at the first launch after installation. Because the latter needs to keep the context of the scan across the installation, a dedicated service or an in-house matching process is prepared separately.