Asynchronous JavaScript And XML, or its acronym Ajax, is a Web development technique for creating interactive web applications. The intent is to shift a great deal of computation to the Web surfer's computer, so the entire Web page does not have to reload when a change is made due to user interaction. This is meant to increase the Web page's interactivity, speed, and usability. The Ajax technique uses a combination of:

• XHTML (or HTML) and CSS for marking up and styling information.
• The Document Object Model manipulated through JavaScript to dynamically display and interact with the information presented
• The XMLHttpRequest object to exchange data asynchronously with the web server. In some Ajax frameworks and in some situations, an IFrame object is used instead of the XMLHttpRequest object to exchange data with the web server.
• XML is commonly used as the format for transfering data, although any format will work, including preformatted HTML, plain text, JSON and even EBML.

Like DHTML, LAMP, or SPA, Ajax is not a technology in itself, but a term that refers to the use of a group of technologies together. In fact, derivative/composite technologies based substantially upon Ajax, such as AFLAX, are already appearing.