ProGuard is a free Java class file shrinker, optimizer, and obfuscator. It can detect and remove unused classes, fields, methods, and attributes. It can then optimize bytecode and remove unused instructions. Finally, it can rename the remaining classes, fields, and methods using short meaningless names. The resulting jars are smaller and harder to reverse-engineer.

More compact jar files also means smaller storage requirements, faster transfer of applications across networks, faster loading, and smaller memory footprints.

ProGuard's main advantage compared to other Java obfuscators is probably its compact template-based configuration. A few intuitive command line options or a simple configuration file are usually sufficient. For instance, the following configuration option preserves all applets in a jar:

    -keep public class * extends java.applet.Applet

The user manual explains all available options and shows more examples of this powerful configuration style.

ProGuard is fast. It only takes seconds to process programs and libraries of several megabytes. The results section presents actual figures for a number of applications.

ProGuard is a command-line tool with an optional graphical user interface. It also comes with plugins for Ant and for the J2ME Wireless Toolkit.

Licence: GPL