Nowadays, there are many design approaches and standards that are used in application development and depend primarily on the platform on which it is displayed. Flat and material design are design systems that are currently most commonly used in mobile app development. Users usually use either an Android or Apple device, depending on their preferences, and they don’t pay attention to the fact that changing the operating system will change the appearance of the application and therefore provide them a different user experience. The aim of this paper is to show what the differences between flat design and material design are and what their impact on user experience is. Google started using material design a few years ago and it has become the standard for creating Android applications. Material Design is an upgraded version of flat design that focuses on details such as animations, shadows and layers. Flat design has been used by Apple and, on the other hand, does not create the impression of multiple dimensions, but rather feels as if objects are "lying" on one surface. In flat design, there are no shadows, gradients, textures, etc., but everything is based on combining fonts, colors, and icons. Skeuomorphism is a design system that is used to gain intuition when using mobile applications. It mimics familiar materials to evoke a sense of comfort and familiarity with the user. Because of this, some icons and graphic elements resemble real-life objects, which is especially evident in the design of icons.