AJAX (Asynchronous JAvaScript and XML) is a Web development technique for creating interactive web applications. The intent is to shift a great deal of interaction to the Web surfer's computer, exchanging data with the server behind the scenes, so that the entire Web page does not have to be reloaded each time the user makes a change. This is meant to increase the Web page's interactivity, speed, and usability.

Prior to AJAX, any retrieval of data from the server required that the entire Web page be refreshed in the user's computer. As a result, systems were often designed with less interaction; for example, to have the user submit a form only at the end, after all fields were filled in. In contrast, AJAX systems can validate one or two items at a time 'behind the scenes' without making the session cumbersome, especially over slow connections. AJAX, also known as 'remote scripting', allows Web-based applications to be designed like LAN-based applications.

The Ajax technique uses a combination of:

• XHTML (or HTML) and CSS for marking up and styling information.
• The DOM accessed with a client-side scripting language, especially ECMAScript implementations like JavaScript and JScript, 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.

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.

Redlaunch utilises AJAX.