It could easily be argued that the 2007 release of the iPhone was the genesis of mobile gaming and the “app-itization” of web content. Sales of content for mobile devices, including phones, tablets, and televisions has numbered in the billions. Although mobile games existed before, the appearance of smartphones was one of the first times that mobile devices could use the Web—the real Web—and not some watered-down version for consuming and producing content. In this chapter, we will discuss in part the dominant mobile phone operating systems, what is involved in developing for them, and some of the frameworks that work with them. Before we go into the how and why, let’s briefly discuss the platforms themselves.