In this chapter, we advanced further with the ArcGIS JavaScript API for mobile development. We looked at the code for four different tools that are often requested by mobile ArcGIS users. These included providing a feature details popup, layer legend, feature search, and address search. We got to use Dojo widgets for the first time. Esri provides many widgets that should greatly help your development efforts. Tools that can be customized are the cornerstone of many ArcGIS mobile apps. This chapter takes us nicely towards our next chapter: providing custom mobile apps that can be used on different devices. Often, users want to access their ArcGIS app on their smartphone, phablet, or tablet. Responsive design is a popular approach to developing web applications that work well on all devices. We will be covering this in the next chapter.