Design for mobile devices today is not an option but a necessity for all businesses. Being on the Internet is not enough, now we must also provide users with an optimal experience on their devices. High mobility, a small screen, short-term use, little attention... are some of the assumptions surrounding the use of these devices. But is this always true? Is there any more information that we should take into account? And besides... Application, mobile web or responsive design? This workshop will discuss the reasons why this is important and discover through practice which the most important aspects to be considered are when designing an application or website.