.JAR File Extension

Java Archive (JAR) file used by the Java Runtime Environment (JRE), a framework used for executing Java programs; can contain .CLASS files, application resources, and an optional manifest file (META-INF/MANIFEST.MF); may serve as a program library or as a standalone program that runs if the JRE is installed on the computer.

Java Archive files are compressed using .ZIP compression and may optionally be digitally signed using the jarsigner tool included with the Java SDK. JAR files may be created with the jar tool, and they can be accessed using Java's java.util.jar API.

JAR files are used by Mozilla Firefox, Thunderbird, SeaMonkey, and Sunbird to store themes and add-ons.

NOTE: Sun Microsystems, the original developers of the Java language, were acquired by Oracle. The Java Runtime Environment is also referred to as the Java Virtual Machine (JVM).