Echo is a platform for building web-based applications that approach the capabilities of rich clients. The applications are developed using a component-oriented and event-driven API, eliminating the need to deal with the "page-based" nature of browsers. To the developer, Echo works just like a user interface toolkit.

The latest iteration, Echo3, features the ability to write applications in either server-side Java or client-side JavaScript. Server-side applications run in any Java Servlet Container and do not require developer knowledge of HTML, HTTP, or JavaScript. Client-side JavaScript-based applications do not require any server at all, but can of course communicate with one via XML or JSON over HTTP. Cross-platform AJAX technology is used for rendering, and no browser plugins are required.

Echo is open-source software, licensed under the Mozilla Public License.

What's new in Echo3?

Echo3 nearly retains the API of Echo2 for end developers, but provides a new web container layer that offers superior performance and extensibility. The new web container also provides the capability to write Echo applications entirely in client-side JavaScript using an API patterned after that of server-side Echo (using the client API is entirely optional, Echo3 applications may also be written entirely in server-side Java). For more information on the major changes, see the Echo3 Feature List.