Responsive design is a common expression at the web today. This thesis was about learning about responsive web design in order to apply it to Windows 8 applications created in C# and XAML. The purpose of this thesis was to learn if responsive design can be used in such applications. This was done by first learning about responsive design through a literature study about responsive web design and then specifying responsive application design. How responsive design can be used in applications was found through research and creation of an example application. No literature was found about responsive design for Windows 8 applications in C# and XAML and therefore most of the results came from own ideas and partly solutions found on different forums. The thesis was performed at Infor in Kista. The example application was a social application which was connected to a social web service developed by Infor. Responsive web design is a technique used for making webpages adapt to the size and resolution of the viewport. This is done by creating a structured, fluid layout by using a flexible grid and flexible images. Media queries are used to set up different states for presenting the page in different ways for different sizes and resolutions of the viewport. In the different states parts of the content can for example be hidden or styled. The number of columns of information can also be set to adapt to make the page easier to view. Responsive design for applications should make the layout of the application adapt to fit the application window of the device used depending on its resolution. One way to specify a responsive design for Windows 8 applications could be to create only one application which could be used on all different Windows 8 platforms, such as phones, tablets and computers. It is probably not possible today to create this one application for different Windows 8 platforms. Another way of specifying responsive design for application is to create a responsive user interface which could be shared and used in the different Windows 8 applications. The latter was the chosen definition for this thesis. The scope of this thesis was limited to only research for responsive design in Windows Store apps and Windows Phone 8 applications. Windows Phone 8 applications are applications used on smartphones with Windows Phone 8 as operating system while Windows Store applications are used on computers with Windows 8 as operating system. Other Windows 8 devices were not included in this thesis. The final conclusion of this thesis was that although it is complicated to use responsive application design it can be used for most of the user interface. A responsive user interface for the applications can be created separately, but some parts of the application pages cannot be shared between the different platforms. This results in a mostly responsive sharable user interface.