Responsive design isn’t just about CSS breakpoints anymore. When you’re working inside classic ASP.NET WebForms — especially with Telerik controls — you have an extra layer of intelligence available to you: server-side device detection. Instead of waiting for the browser to decide how your layout should behave, Telerik lets you detect the visitor’s device size on the server and adjust your UI before the page even renders.
This is incredibly useful when you’re dealing with controls like RadSiteMap, RadMenu, or RadGrid, where layout decisions often need to be made early in the page lifecycle. The snippet below shows exactly how to detect a small-screen device and automatically switch your site map into a single-column layout for mobile users.