The World Wide Web is amidst a transition from interactive websites to web applications. An increasing number of users perform their daily computing tasks entirely within the web browser, turning the Web into an important platform for application development. The Web as a platform, however, lacks the computational performance of native applications. This problem has motivated the inception of native web applications, e.g. Microsoft Xax and Google Native Client (NaCl), that allow the extension of conventional web applications with compiled native code. This book outlines the benefits and drawbacks of native web applications. An experimental performance analysis is undertaken in order to analyze and compare the performance characteristics of native C applications, JavaScript web applications, and NaCl native web applications. The results of the performance analysis are complemented with an evaluation on the basis of technical and non-technical criteria and a discussion of the technical, political, and strategic drivers for NaCl.