Writing 3D applications for the browser is possible since some years due to the WebGL API. But since Virtual Reality and Augmented Reality are getting more popular, web developers and designers now have a serious reason to get to know the 3D web, its APIs and design patterns. In this talk you will learn how to create 3D applications in the browser, using ReactJS in combination with popular VR libraries, like A-Frame and ReactVR. You will also see what is necessary to create a Virtual Reality app that runs on common VR devices, and how to create Augmented Reality applications for Android and iOS phones. Since 3D user interfaces and interactions in the browser are relatively new for designers and users, there are no established UX design patterns yet, but you will get to know best-practices and see some tips for improving the usability of your 3d application. The talk ends with my advice on how to create responsible applications, that won’t harm your users – neither physically nor psychologically.