The document summarizes a survey of over 6,000 mobile app developers on their platform usage, revenues, tools, and motivations. On average, developers use 2.9 platforms in Q3 2013, up from 2.7 in 2012. HTML5 is entrenched as the third most popular platform behind iOS and Android. The gap in average revenue from iOS versus Android is closing. The survey also examines which platform developers prioritize, which aspects are most important, how new apps are planned, the tools used, and whether developers are motivated more by money or creativity.