In this chapter, you learned the basics of developing an ArcGIS mobile web application. Before coding, it is often a good idea to set up your environment properly. This was why we spent time considering IDEs, debugging tools, and mobile device emulators. Since ultimately your users will be accessing your mobile application via a web server, we think that having Apache or an equivalent software installed locally would be a good idea for ongoing development testing. The core of the chapter was devoted to coding, walking through, and step-by-step building of your first mobile application using the ArcGIS API. We began by putting in place the core code elements, which allowed us to load a basemap. From there, we added a feature layer, event handler, and finally a geolocation functionality. In the next chapter, we will develop this code further and add some more advanced functionality.