Optional packages are the new name for what used to be known as standard extensions .
The extension mechanism also provides a way for needed optional packages to be retrieved from specified URLs when they are not already installed in the Java 2 SDK or Runtime Environment. Enhancements Enhancements to the extension mechanism in version 1.3 of the Java 2 SDK include an extended set of manifest attributes that can be used for checking vendor and versioning information of installed optional packages. For more information, see Optional-Package Versioning . Overview Overview - What optional packages are and how to use them. Extension Mechanism Architecture Extension Mechanism Architecture - Notes on the extension mechanism API and how optional packages use the Jar file format.