As the internet becomes more widespread, the number and variety of the devices through which users access the internet has also grown. While websites were once accessed primarily via desktop computers, the proportion of website page views via mobile devices is increasing. In Asia and Africa, for example, more than 60 percent of website calls were made via mobile devices in 2018, while in Europe the share was just under 38 percent (Statista Research Department, 2019).

Responsive user interfaces offer a way to present website content in a user-friendly and visually pleasing way on various screen sizes. We will look at the basics of responsive user interfaces, some of their challenges, and what should be considered when designing responsive websites.

The term responsive web design refers to a collection of measures that aim to design a website in such a way that it is optimally adapted for various visual output devices. For example, a smartphone in landscape or portrait mode can serve as the visual output device for the website. Alternatively, a smart watch, tablet, laptop, large monitor, or even a high-resolution television screen could be used for this purpose. Thus, screen sizes can vary greatly. A responsive website is designed so that its content can be optimally adapted to different display sizes, which is illustrated below with the example of the IU website. Users often have different devices through which they want to access website content. Thus, it is necessary that the mobile variant communicates the same content as a desktop variant. The visual design and structural layout must also not change too much so that users do not get lost.