This chapter discusses multiple technologies related to RESTful web services. It discusses Asynchronous JavaScript and XML (AJAX). The chapter examines Java servlets, which can be used as an enabling technology for Java Application Programming Interface (API) for RESTful Web Services JAX-RS. It also discusses how Internet Media Types are handled by JAX-RS. A RESTful web service is client/server-based, and does not store state. RESTful web services make use of the basic functionality of the World Wide Web: They use the Hypertext Transfer Protocol (HTTP) protocol, and they use Internet Media types. In general they are stateless. Java Servlets date back to the late 1990s at Sun Microsystems. AJAX is a name for a collection of technologies that are used together on the client so that a user's web page is updated a piece at a time, in the background so the user can continue to do other work in the meantime.