Rich Internet applications (RIAs) are web applications that have most of the characteristics of desktop applications, typically delivered either by way of a standards based web browser, via a browser plug-in, or independently via sandboxes or virtual machines. Examples of RIA frameworks include Ajax, Curl, GWT, Adobe Flash/Adobe Flex/AIR, Java/JavaFX, Mozilla's XUL and Microsoft Silverlight.
The term was introduced in March 2002 by vendors like Macromedia who were addressing limitations at the time in the "richness of the application interfaces, media and content, and the overall sophistication of the solutions" by introducing proprietary extensions. There has been some debate about whether Ajax properly qualifies as an RIA or whether the term should be reserved for plug-in based technologies. However Ajax clearly demonstrates all the core characteristics of an RIA and current opinion appears to hold that it should be therefore be included in this category.