The extension environment, also known as the ext environment, is a set of tools that allow developers to build portals and portlets on top of Liferay Portal. It can be seen as a Software Development Kit that is independent of any IDE but that integrates well with all of them thanks to its usage of ant, the most popular and supported build tool. Another way to think about the extension environment is as a wrapper for Liferay's core source because in most cases, it mirrors Liferay's core source directories (i.e. ext-ejb/ for portal-ejb/, ext-web/ for portal-web/). It allows you to develop on top of Liferay portal, like a platform, providing help when an upgrade to a new version of Liferay Portal is needed.

The following instructions explain how to use the environment and are meant to keep custom code separated from the Liferay Portal code so that upgrades can be made easily. The Ant scripts referred to by these instructions are only available for JBoss+Jetty, JBoss+Tomcat, OracleAS, Orion, RexIP, and Weblogic and have not yet been made available for the other supported application servers.