Examples

Some typical useful configurations:
  1. A typical application
  2. A typical applet
  3. A typical midlet
  4. A typical Java Card applet
  5. A typical xlet
  6. A simple Android activity
  7. A complete Android application
  8. A typical library
  9. All possible applications in the input jars
  10. All possible applets in the input jars
  11. All possible midlets in the input jars
  12. All possible Java Card applets in the input jars
  13. All possible xlets in the input jars
  14. All possible servlets in the input jars
  15. Scala applications with the Scala runtime
  16. Processing native methods
  17. Processing callback methods
  18. Processing enumeration classes
  19. Processing serializable classes
  20. Processing bean classes
  21. Processing annotations
  22. Processing database drivers
  23. Processing ComponentUI classes
  24. Processing RMI code
  25. Processing resource injection
  26. Processing resource files
  27. Processing manifest files
  28. Producing useful obfuscated stack traces
  29. Obfuscating package names
  30. Removing logging code
  31. Restructuring the output archives
  32. Filtering the input and the output
  33. Processing multiple applications at once
  34. Incremental obfuscation
  35. Preverifying class files for Java Micro Edition
  36. Upgrading class files to Java 6
  37. Finding dead code
  38. Printing out the internal structure of class files
  39. Using annotations to configure ProGuard
You can find some sample configuration files in the examples directory of the ProGuard distribution.

A typical application

To shrink, optimize, and obfuscate a simple Java application, you typically create a configuration file like myconfig.pro, which can be used with
bin/proguard @myconfig.pro

The configuration file specifies the input, the output, and the entry points of the application:

-injars       myapplication.jar
-outjars      myapplication_out.jar
-libraryjars  <java.home>/lib/rt.jar
-printmapping myapplication.map

-keep public class mypackage.MyMain {
    public static void main(java.lang.String[]);
}

Note the use of the <java.home> system property. ProGuard automatically replaces it when parsing the file.

The -keep option specifies the entry point of the application that has to be preserved. The access modifiers public and static are not really required in this case, since we know a priori that the specified class and method have the proper access flags. It just looks more familiar this way.

Note that all type names are fully specified: mypackage.MyMain and java.lang.String[].

We're writing out an obfuscation mapping file with -printmapping, for de-obfuscating any stack traces later on, or for incremental obfuscation of extensions.

We can further improve the results with a few additional options:

-optimizationpasses 3
-overloadaggressively
-repackageclasses ''
-allowaccessmodification
These options are not required; they just shave off some extra bytes from the output jar, by performing up to 3 optimization passes, and by aggressively obfuscating class members and package names.

In general, you might need a few additional options for processing native methods, callback methods, enumerations, serializable classes, bean classes, annotations, and resource files.

A typical applet

These options shrink, optimize, and obfuscate the applet mypackage.MyApplet:
-injars      in.jar
-outjars     out.jar
-libraryjars <java.home>/lib/rt.jar

-keep public class mypackage.MyApplet

The typical applet methods will be preserved automatically, since mypackage.MyApplet is an extension of the Applet class in the library rt.jar.

If applicable, you should add options for processing native methods, callback methods, enumerations, serializable classes, bean classes, annotations, and resource files.

A typical midlet

These options shrink, optimize, obfuscate, and preverify the midlet mypackage.MyMIDlet:
-injars      in.jar
-outjars     out.jar
-libraryjars /usr/local/java/wtk2.5.2/lib/midpapi20.jar
-libraryjars /usr/local/java/wtk2.5.2/lib/cldcapi11.jar
-overloadaggressively
-repackageclasses ''
-allowaccessmodification
-microedition

-keep public class mypackage.MyMIDlet

Note how we're now targeting the Java Micro Edition run-time environment of midpapi20.jar and cldcapi11.jar, instead of the Java Standard Edition run-time environment rt.jar. You can target other JME environments by picking the appropriate jars.

The typical midlet methods will be preserved automatically, since mypackage.MyMIDlet is an extension of the MIDlet class in the library midpapi20.jar.

The -microedition option makes sure the class files are preverified for Java Micro Edition, producing compact StackMap attributes. It is no longer necessary to run an external preverifier.

Be careful if you do use the external preverify tool on a platform with a case-insensitive filing system, such as Windows. Because this tool unpacks your processed jars, you should then use ProGuard's -dontusemixedcaseclassnames option.

If applicable, you should add options for processing native methods and resource files.

Note that you will still have to adapt the midlet jar size in the corresponding jad file; ProGuard doesn't do that for you.

A typical Java Card applet

These options shrink, optimize, and obfuscate the Java Card applet mypackage.MyApplet:
-injars      in.jar
-outjars     out.jar
-libraryjars /usr/local/java/javacard2.2.2/lib/api.jar
-dontwarn    java.lang.Class
-overloadaggressively
-repackageclasses ''
-allowaccessmodification

-keep public class mypackage.MyApplet

The configuration is very similar to the configuration for midlets, except that it now targets the Java Card run-time environment. This environment doesn't have java.lang.Class, so we're telling ProGuard not to worry about it.

A typical xlet

These options shrink, optimize, and obfuscate the xlet mypackage.MyXlet:
-injars      in.jar
-outjars     out.jar
-libraryjars /usr/local/java/jtv1.1/javatv.jar
-libraryjars /usr/local/java/cdc1.1/lib/cdc.jar
-libraryjars /usr/local/java/cdc1.1/lib/btclasses.zip
-overloadaggressively
-repackageclasses ''
-allowaccessmodification

-keep public class mypackage.MyXlet

The configuration is very similar to the configuration for midlets, except that it now targets the CDC run-time environment with the Java TV API.

A simple Android activity

These options shrink, optimize, and obfuscate the single Android activity mypackage.MyActivity:
-injars      bin/classes
-outjars     bin/classes-processed.jar
-libraryjars /usr/local/java/android-sdk/platforms/android-9/android.jar

-dontpreverify
-repackageclasses ''
-allowaccessmodification
-optimizations !code/simplification/arithmetic

-keep public class mypackage.MyActivity

We're targeting the Android run-time and keeping the activity as an entry point.

Preverification is irrelevant for the dex compiler and the Dalvik VM, so we can switch it off with the -dontpreverify option.

The -optimizations option disables some arithmetic simplifications that Dalvik 1.0 and 1.5 can't handle. Note that the Dalvik VM also can't handle aggressive overloading (of static fields).

If applicable, you should add options for processing native methods, callback methods, enumerations, annotations, and resource files.

A complete Android application

attention The Ant and Eclipse build processes of the Android SDK already integrate ProGuard by default, with all the proper settings. You only need to enable ProGuard (for release builds), by uncommenting the line "proguard.config=....." in the file project.properties (created or updated by Android SDK revision 17 or higher). Notes:

For more information, you can consult the official Developer Guide in the Android SDK.

If you're constructing a build process from scratch: these options shrink, optimize, and obfuscate all public activities, services, broadcast receivers, and content providers from the compiled classes and external libraries:

-injars      bin/classes
-injars      libs
-outjars     bin/classes-processed.jar
-libraryjars /usr/local/java/android-sdk/platforms/android-9/android.jar

-dontpreverify
-repackageclasses ''
-allowaccessmodification
-optimizations !code/simplification/arithmetic
-keepattributes *Annotation*

-keep public class * extends android.app.Activity
-keep public class * extends android.app.Application
-keep public class * extends android.app.Service
-keep public class * extends android.content.BroadcastReceiver
-keep public class * extends android.content.ContentProvider

-keep public class * extends android.view.View {
    public <init>(android.content.Context);
    public <init>(android.content.Context, android.util.AttributeSet);
    public <init>(android.content.Context, android.util.AttributeSet, int);
    public void set*(...);
}

-keepclasseswithmembers class * {
    public <init>(android.content.Context, android.util.AttributeSet);
}

-keepclasseswithmembers class * {
    public <init>(android.content.Context, android.util.AttributeSet, int);
}

-keepclassmembers class * extends android.content.Context {
   public void *(android.view.View);
   public void *(android.view.MenuItem);
}

-keepclassmembers class * implements android.os.Parcelable {
    static ** CREATOR;
}

-keepclassmembers class **.R$* {
    public static <fields>;
}

-keepclassmembers class * {
    @android.webkit.JavascriptInterface <methods>;
}

Most importantly, we're keeping all fundamental classes that may be referenced by the AndroidManifest.xml file of the application. If your manifest file contains other classes and methods, you may have to specify those as well.

We're keeping annotations, since they might be used by custom RemoteViews.

We're keeping any custom View extensions and other classes with typical constructors, since they might be referenced from XML layout files.

We're also keeping possible onClick handlers in custom Context extensions, since they might be referenced from XML layout files.

We're also keeping the required static fields in Parcelable implementations, since they are accessed by introspection.

We're keeping the static fields of referenced inner classes of auto-generated R classes, just in case your code is accessing those fields by introspection. Note that the compiler already inlines primitive fields, so ProGuard can generally remove all these classes entirely anyway (because the classes are not referenced and therefore not required).

Finally, we're keeping annotated Javascript interface methods, so they can be exported and accessed by their original names. Javascript interface methods that are not annotated (in code targeted at Android versions older than 4.2) still need to be preserved manually.

If you're using additional Google APIs, you'll have to specify those as well, for instance:

-libraryjars /usr/local/android-sdk/add-ons/google_apis-7_r01/libs/maps.jar

If you're using Google's optional License Verification Library, you can obfuscate its code along with your own code. You do have to preserve its ILicensingService interface for the library to work:

-keep public interface com.android.vending.licensing.ILicensingService

If you're using the Android Compatibility library, you should add the following line, to let ProGuard know it's ok that the library references some classes that are not available in all versions of the API:

-dontwarn android.support.**

If applicable, you should add options for processing native methods, callback methods, enumerations, and resource files. You may also want to add options for producing useful stack traces and to remove logging. You can find a complete sample configuration in examples/android.pro in the ProGuard distribution.

A typical library

These options shrink, optimize, and obfuscate an entire library, keeping all public and protected classes and class members, native method names, and serialization code. The processed version of the library can then still be used as such, for developing code based on its public API.
-injars       in.jar
-outjars      out.jar
-libraryjars  <java.home>/lib/rt.jar
-printmapping out.map

-keepparameternames
-renamesourcefileattribute SourceFile
-keepattributes Exceptions,InnerClasses,Signature,Deprecated,
                SourceFile,LineNumberTable,*Annotation*,EnclosingMethod

-keep public class * {
    public protected *;
}

-keepclassmembernames class * {
    java.lang.Class class$(java.lang.String);
    java.lang.Class class$(java.lang.String, boolean);
}

-keepclasseswithmembernames class * {
    native <methods>;
}

-keepclassmembers,allowoptimization enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}

-keepclassmembers class * implements java.io.Serializable {
    static final long serialVersionUID;
    private static final java.io.ObjectStreamField[] serialPersistentFields;
    private void writeObject(java.io.ObjectOutputStream);
    private void readObject(java.io.ObjectInputStream);
    java.lang.Object writeReplace();
    java.lang.Object readResolve();
}

This configuration should preserve everything we'll ever want to access in the library. Only if there are any other non-public classes or methods that are invoked dynamically, they should be specified using additional -keep options.

The -keepclassmembernames option for the class$ methods is not strictly necessary. These methods are inserted by the javac compiler and the jikes compiler respectively, in JDK 1.2 and older, to implement the .class construct. ProGuard will automatically detect them and deal with them, even when their names have been obfuscated. However, other obfuscators may rely on the original method names. It may therefore be helpful to preserve them, in case these other obfuscators are ever used for further obfuscation of the library.

The "Exceptions" attribute has to be preserved, so the compiler knows which exceptions methods may throw.

The "InnerClasses" attribute (or more precisely, its source name part) has to be preserved too, for any inner classes that can be referenced from outside the library. The javac compiler would be unable to find the inner classes otherwise.

The "Signature" attribute is required to be able to access generic types when compiling in JDK 5.0 and higher.

The -keepparameternames option keeps the parameter names in the "LocalVariableTable" and "LocalVariableTypeTable" attributes of public library methods. Some IDEs can present these names to the developers who use the library.

Finally, we're keeping the "Deprecated" attribute and the attributes for producing useful stack traces.

We've also added some options for for processing native methods, enumerations, serializable classes, and annotations, which are all discussed in their respective examples.

All possible applications in the input jars

These options shrink, optimize, and obfuscate all public applications in in.jar:
-injars      in.jar
-outjars     out.jar
-libraryjars <java.home>/lib/rt.jar
-printseeds

-keepclasseswithmembers public class * {
    public static void main(java.lang.String[]);
}

Note the use of -keepclasseswithmembers. We don't want to preserve all classes, just all classes that have main methods, and those methods.

The -printseeds option prints out which classes exactly will be preserved, so we know for sure we're getting what we want.

If applicable, you should add options for processing native methods, callback methods, enumerations, serializable classes, bean classes, annotations, and resource files.

All possible applets in the input jars

These options shrink, optimize, and obfuscate all public applets in in.jar:
-injars      in.jar
-outjars     out.jar
-libraryjars <java.home>/lib/rt.jar
-printseeds

-keep public class * extends java.applet.Applet

We're simply keeping all classes that extend the Applet class.

Again, the -printseeds option prints out which applets exactly will be preserved.

If applicable, you should add options for processing native methods, callback methods, enumerations, serializable classes, bean classes, annotations, and resource files.

All possible midlets in the input jars

These options shrink, optimize, obfuscate, and preverify all public midlets in in.jar:
-injars      in.jar
-outjars     out.jar
-libraryjars /usr/local/java/wtk2.5.2/lib/midpapi20.jar
-libraryjars /usr/local/java/wtk2.5.2/lib/cldcapi11.jar
-overloadaggressively
-repackageclasses ''
-allowaccessmodification
-microedition
-printseeds

-keep public class * extends javax.microedition.midlet.MIDlet

We're simply keeping all classes that extend the MIDlet class.

The -microedition option makes sure the class files are preverified for Java Micro Edition, producing compact StackMap attributes. It is no longer necessary to run an external preverifier.

Be careful if you do use the external preverify tool on a platform with a case-insensitive filing system, such as Windows. Because this tool unpacks your processed jars, you should then use ProGuard's -dontusemixedcaseclassnames option.

The -printseeds option prints out which midlets exactly will be preserved.

If applicable, you should add options for processing native methods and resource files.

Note that you will still have to adapt the midlet jar size in the corresponding jad file; ProGuard doesn't do that for you.

All possible Java Card applets in the input jars

These options shrink, optimize, and obfuscate all public Java Card applets in in.jar:
-injars      in.jar
-outjars     out.jar
-libraryjars /usr/local/java/javacard2.2.2/lib/api.jar
-dontwarn    java.lang.Class
-overloadaggressively
-repackageclasses ''
-allowaccessmodification
-printseeds

-keep public class * implements javacard.framework.Applet

We're simply keeping all classes that implement the Applet interface.

The -printseeds option prints out which applets exactly will be preserved.

All possible xlets in the input jars

These options shrink, optimize, and obfuscate all public xlets in in.jar:
-injars      in.jar
-outjars     out.jar
-libraryjars /usr/local/java/jtv1.1/javatv.jar
-libraryjars /usr/local/java/cdc1.1/lib/cdc.jar
-libraryjars /usr/local/java/cdc1.1/lib/btclasses.zip
-overloadaggressively
-repackageclasses ''
-allowaccessmodification
-printseeds

-keep public class * implements javax.tv.xlet.Xlet

We're simply keeping all classes that implement the Xlet interface.

The -printseeds option prints out which xlets exactly will be preserved.

All possible servlets in the input jars

These options shrink, optimize, and obfuscate all public servlets in in.jar:
-injars      in.jar
-outjars     out.jar
-libraryjars <java.home>/lib/rt.jar
-libraryjars /usr/local/java/servlet/servlet.jar
-printseeds

-keep public class * implements javax.servlet.Servlet

Keeping all servlets is very similar to keeping all applets. The servlet API is not part of the standard run-time jar, so we're specifying it as a library. Don't forget to use the right path name.

We're then keeping all classes that implement the Servlet interface. We're using the implements keyword because it looks more familiar in this context, but it is equivalent to extends, as far as ProGuard is concerned.

The -printseeds option prints out which servlets exactly will be preserved.

If applicable, you should add options for processing native methods, callback methods, enumerations, serializable classes, bean classes, annotations, and resource files.

Scala applications with the Scala runtime

These options shrink, optimize, and obfuscate all public Scala applications in in.jar:
-injars      in.jar
-injars      /usr/local/java/scala-2.9.1/lib/scala-library.jar
-outjars     out.jar
-libraryjars <java.home>/lib/rt.jar

-dontwarn scala.**

-keepclasseswithmembers public class * {
    public static void main(java.lang.String[]);
}

-keep class * implements org.xml.sax.EntityResolver

-keepclassmembers class * {
    ** MODULE$;
}

-keepclassmembernames class scala.concurrent.forkjoin.ForkJoinPool {
    long eventCount;
    int  workerCounts;
    int  runControl;
    scala.concurrent.forkjoin.ForkJoinPool$WaitQueueNode syncStack;
    scala.concurrent.forkjoin.ForkJoinPool$WaitQueueNode spareStack;
}

-keepclassmembernames class scala.concurrent.forkjoin.ForkJoinWorkerThread {
    int base;
    int sp;
    int runState;
}

-keepclassmembernames class scala.concurrent.forkjoin.ForkJoinTask {
    int status;
}

-keepclassmembernames class scala.concurrent.forkjoin.LinkedTransferQueue {
    scala.concurrent.forkjoin.LinkedTransferQueue$PaddedAtomicReference head;
    scala.concurrent.forkjoin.LinkedTransferQueue$PaddedAtomicReference tail;
    scala.concurrent.forkjoin.LinkedTransferQueue$PaddedAtomicReference cleanMe;
}

The configuration is essentially the same as for processing applications, because Scala is compiled to ordinary Java bytecode. However, the example processes the Scala runtime library as well. The processed jar can be an order of magnitude smaller and a few times faster than the original code (for the Scala code examples, for instance).

The -dontwarn option tells ProGuard not to complain about some artefacts in the Scala runtime, the way it is compiled by the scalac compiler (at least in Scala 2.9.1 and older). Note that this option should always be used with care.

The additional -keep options make sure that some classes and some fields that are accessed by means of introspection are not removed or renamed.

If applicable, you should add options for processing native methods, callback methods, enumerations, serializable classes, bean classes, annotations, and resource files.

Processing native methods

If your application, applet, servlet, library, etc., contains native methods, you'll want to preserve their names and their classes' names, so they can still be linked to the native library. The following additional option will ensure that:
-keepclasseswithmembernames class * {
    native <methods>;
}

Note the use of -keepclasseswithmembernames. We don't want to preserve all classes or all native methods; we just want to keep the relevant names from being obfuscated.

ProGuard doesn't look at your native code, so it won't automatically preserve the classes or class members that are invoked by the native code. These are entry points, which you'll have to specify explicitly. Callback methods are discussed below as a typical example.

Processing callback methods

If your application, applet, servlet, library, etc., contains callback methods, which are called from external code (native code, scripts,...), you'll want to preserve them, and probably their classes too. They are just entry points to your code, much like, say, the main method of an application. If they aren't preserved by other -keep options, something like the following option will keep the callback class and method:
-keep class mypackage.MyCallbackClass {
    void myCallbackMethod(java.lang.String);
}

This will preserve the given class and method from being removed or renamed.

Processing enumeration classes

If your application, applet, servlet, library, etc., contains enumeration classes, you'll have to preserve some special methods. Enumerations were introduced in Java 5. The java compiler translates enumerations into classes with a special structure. Notably, the classes contain implementations of some static methods that the run-time environment accesses by introspection (Isn't that just grand? Introspection is the self-modifying code of a new generation). You have to specify these explicitly, to make sure they aren't removed or obfuscated:
-keepclassmembers,allowoptimization enum * {
    public static **[] values();
    public static ** valueOf(java.lang.String);
}

Processing serializable classes

More complex applications, applets, servlets, libraries, etc., may contain classes that are serialized. Depending on the way in which they are used, they may require special attention:

Note that the above options may preserve more classes and class members than strictly necessary. For instance, a large number of classes may implement the Serialization interface, yet only a small number may actually ever be serialized. Knowing your application and tuning the configuration often produces more compact results.

Processing bean classes

If your application, applet, servlet, library, etc., makes extensive use of introspection on bean classes to find bean editor classes, or getter and setter methods, then configuration may become painful. There's not much else you can do than making sure the bean class names, or the getter and setter names don't change. For instance:
-keep public class mypackage.MyBean {
    public void setMyProperty(int);
    public int getMyProperty();
}

-keep public class mypackage.MyBeanEditor

If there are too many elements to list explicitly, wildcards in class names and method signatures might be helpful. This example preserves all possible setters and getters in classes in the package mybeans:

-keep class mybeans.** {
    void set*(***);
    void set*(int, ***);

    boolean is*(); 
    boolean is*(int);

    *** get*();
    *** get*(int);
}

The '***' wildcard matches any type (primitive or non-primitive, array or non-array). The methods with the 'int' arguments matches properties that are lists.

Processing annotations

If your application, applet, servlet, library, etc., uses annotations, you may want to preserve them in the processed output. Annotations are represented by attributes that have no direct effect on the execution of the code. However, their values can be retrieved through introspection, allowing developers to adapt the execution behavior accordingly. By default, ProGuard treats annotation attributes as optional, and removes them in the obfuscation step. If they are required, you'll have to specify this explicitly:
-keepattributes *Annotation*

For brevity, we're specifying a wildcarded attribute name, which will match RuntimeVisibleAnnotations, RuntimeInvisibleAnnotations, RuntimeVisibleParameterAnnotations, RuntimeInvisibleParameterAnnotations, and AnnotationDefault. Depending on the purpose of the processed code, you could refine this selection, for instance not keeping the run-time invisible annotations (which are only used at compile-time).

Some code may make further use of introspection to figure out the enclosing methods of anonymous inner classes. In that case, the corresponding attribute has to be preserved as well:

-keepattributes EnclosingMethod

Processing database drivers

Database drivers are implementations of the Driver interface. Since they are often created dynamically, you may want to preserve any implementations that you are processing as entry points:
-keep class * implements java.sql.Driver

This option also gets rid of the note that ProGuard prints out about (java.sql.Driver)Class.forName constructs, if you are instantiating a driver in your code (without necessarily implementing any drivers yourself).

Processing ComponentUI classes

Swing UI look and feels are implemented as extensions of the ComponentUI class. For some reason, these have to contain a static method createUI, which the Swing API invokes using introspection. You should therefore always preserve the method as an entry point, for instance like this:
-keep class * extends javax.swing.plaf.ComponentUI {
    public static javax.swing.plaf.ComponentUI createUI(javax.swing.JComponent);
}

This option also keeps the classes themselves.

Processing RMI code

Reportedly, the easiest way to handle RMI code is to process the code with ProGuard first and then invoke the rmic tool. If that is not possible, you may want to try something like this:
-keepattributes Exceptions

-keep interface * extends java.rmi.Remote {
    <methods>;
}

-keep class * implements java.rmi.Remote {
    <init>(java.rmi.activation.ActivationID, java.rmi.MarshalledObject);
}

The first -keep option keeps all your Remote interfaces and their methods. The second one keeps all the implementations, along with their particular RMI constructors, if any.

The Exceptions attribute has to be kept too, because the RMI handling code performs introspection to check whether the method signatures are compatible.

Processing resource injection

If your application is using JEE-style resource injection, the application container will automatically assign instances of resource classes to fields and methods that are annotated with @Resource. The container applies introspection, even accessing private class members directly. It typically constructs a resource name based on the type name and the class member name. We then have to avoid that such class members are removed or renamed:
-keepclassmembers class * {
    @javax.annotation.Resource *;
}

The Spring framework has another similar annotation @Autowired:

-keepclassmembers class * {
    @org.springframework.beans.factory.annotation.Autowired *;
}

Processing resource files

If your application, applet, servlet, library, etc., contains resource files, it may be necessary to adapt their names and/or their contents when the application is obfuscated. The following two options can achieve this automatically:
-adaptresourcefilenames    **.properties,**.gif,**.jpg
-adaptresourcefilecontents **.properties,META-INF/MANIFEST.MF

The -adaptresourcefilenames option in this case renames properties files and image files in the processed output, based on the obfuscated names of their corresponding class files (if any). The -adaptresourcefilecontents option looks for class names in properties files and in the manifest file, and replaces these names by the obfuscated names (if any). You'll probably want to adapt the filters to suit your application.

Processing manifest files

As illustrated in the previous section, manifest files can be treated like ordinary resource files. ProGuard can adapt obfuscated class names in the files, but it won't make any other changes. If you want anything else, you should apply an external tool. For instance, if a manifest file contains signing information, you should sign the jar again after it has been processed.

If you're merging several input jars into a single output jar, you'll have to pick one, typically by specifying filters:

-injars  in1.jar
-injars  in2.jar(!META-INF/MANIFEST.MF)
-injars  in3.jar(!META-INF/MANIFEST.MF)
-outjars out.jar

The filters will let ProGuard copy the manifest file from the first jar and ignore any manifest files in the second and third input jars. Note that ProGuard will leave the order of the files in the jars unchanged; manifest files are not necessarily put first.

Producing useful obfuscated stack traces

These options let obfuscated applications or libraries produce stack traces that can still be deciphered later on:
-printmapping out.map

-renamesourcefileattribute SourceFile
-keepattributes SourceFile,LineNumberTable

We're keeping all source file attributes, but we're replacing their values by the string "SourceFile". We could use any string. This string is already present in all class files, so it doesn't take up any extra space. If you're working with J++, you'll want to keep the "SourceDir" attribute as well.

We're also keeping the line number tables of all methods.

Whenever both of these attributes are present, the Java run-time environment will include line number information when printing out exception stack traces.

The information will only be useful if we can map the obfuscated names back to their original names, so we're saving the mapping to a file out.map. The information can then be used by the ReTrace tool to restore the original stack trace.

Obfuscating package names

Package names can be obfuscated in various ways, with increasing levels of obfuscation and compactness. For example, consider the following classes:
mycompany.myapplication.MyMain
mycompany.myapplication.Foo
mycompany.myapplication.Bar
mycompany.myapplication.extra.FirstExtra
mycompany.myapplication.extra.SecondExtra
mycompany.util.FirstUtil
mycompany.util.SecondUtil

Let's assume the class name mycompany.myapplication.MyMain is the main application class that is kept by the configuration. All other class names can be obfuscated.

By default, packages that contain classes that can't be renamed aren't renamed either, and the package hierarchy is preserved. This results in obfuscated class names like these:

mycompany.myapplication.MyMain
mycompany.myapplication.a
mycompany.myapplication.b
mycompany.myapplication.a.a
mycompany.myapplication.a.b
mycompany.a.a
mycompany.a.b

The -flattenpackagehierarchy option obfuscates the package names further, by flattening the package hierarchy of obfuscated packages:

-flattenpackagehierarchy 'myobfuscated'

The obfuscated class names then look as follows:

mycompany.myapplication.MyMain
mycompany.myapplication.a
mycompany.myapplication.b
myobfuscated.a.a
myobfuscated.a.b
myobfuscated.b.a
myobfuscated.b.b

Alternatively, the -repackageclasses option obfuscates the entire packaging, by combining obfuscated classes into a single package:

-repackageclasses 'myobfuscated'
The obfuscated class names then look as follows:
mycompany.myapplication.MyMain
mycompany.myapplication.a
mycompany.myapplication.b
myobfuscated.a
myobfuscated.b
myobfuscated.c
myobfuscated.d

Additionally specifying the -allowaccessmodification option allows access permissions of classes and class members to be broadened, opening up the opportunity to repackage all obfuscated classes:

-repackageclasses 'myobfuscated'
-allowaccessmodification
The obfuscated class names then look as follows:
mycompany.myapplication.MyMain
myobfuscated.a
myobfuscated.b
myobfuscated.c
myobfuscated.d
myobfuscated.e
myobfuscated.f

The specified target package can always be the root package. For instance:

-repackageclasses ''
-allowaccessmodification
The obfuscated class names are then the shortest possible names:
mycompany.myapplication.MyMain
a
b
c
d
e
f

Note that not all levels of obfuscation of package names may be acceptable for all code. Notably, you may have to take into account that your application may contain resource files that have to be adapted.

Removing logging code

You can let ProGuard remove logging code. The trick is to specify that the logging methods don't have side-effects — even though they actually do, since they write to the console or to a log file. ProGuard will take your word for it and remove the invocations (in the optimization step) and if possible the logging classes and methods themselves (in the shrinking step).

For example, this configuration removes invocations of the Android logging methods:

-assumenosideeffects class android.util.Log {
    public static boolean isLoggable(java.lang.String, int);
    public static int v(...);
    public static int i(...);
    public static int w(...);
    public static int d(...);
    public static int e(...);
}

The wildcards are a shortcut to match all versions of the methods.

Note that you generally can't remove logging code that uses System.out.println, since you would be removing all invocations of java.io.PrintStream#println, which could break your application. You can work around it by creating your own logging methods and let ProGuard remove those.

Restructuring the output archives

In simple applications, all output classes and resources files are merged into a single jar. For example:
-injars  classes
-injars  in1.jar
-injars  in2.jar
-injars  in3.jar
-outjars out.jar

This configuration merges the processed versions of the files in the classes directory and the three jars into a single output jar out.jar.

If you want to preserve the structure of your input jars (and/or wars, ears, zips, or directories), you can specify an output directory (or a war, an ear, or a zip). For example:

-injars  in1.jar
-injars  in2.jar
-injars  in3.jar
-outjars out

The input jars will then be reconstructed in the directory out, with their original names.

You can also combine archives into higher level archives. For example:

-injars  in1.jar
-injars  in2.jar
-injars  in3.jar
-outjars out.war

The other way around, you can flatten the archives inside higher level archives into simple archives:

-injars  in.war
-outjars out.jar

This configuration puts the processed contents of all jars inside in.war (plus any other contents of in.war) into out.jar.

If you want to combine input jars (and/or wars, ears, zips, or directories) into output jars (and/or wars, ears, zips, or directories), you can group the -injars and -outjars options. For example:

-injars base_in1.jar
-injars base_in2.jar
-injars base_in3.jar
-outjars base_out.jar

-injars  extra_in.jar
-outjars extra_out.jar

This configuration puts the processed results of all base_in*.jar jars into base_out.jar, and the processed results of the extra_in.jar into extra_out.jar. Note that only the order of the options matters; the additional whitespace is just for clarity.

This grouping, archiving, and flattening can be arbitrarily complex. ProGuard always tries to package output archives in a sensible way, reconstructing the input entries as much as required.

Filtering the input and the output

If you want even greater control, you can add filters to the input and the output, filtering out zips, ears, wars, jars, and/or ordinary files. For example, if you want to disregard certain files from an input jar:
-injars  in.jar(!images/**)
-outjars out.jar

This configuration removes any files in the images directory and its subdirectories.

Such filters can be convenient for avoiding warnings about duplicate files in the output. For example, only keeping the manifest file from a first input jar:

-injars  in1.jar
-injars  in2.jar(!META-INF/MANIFEST.MF)
-injars  in3.jar(!META-INF/MANIFEST.MF)
-outjars out.jar

Another useful application is speeding up the processing by ProGuard, by disregarding a large number of irrelevant classes in the runtime library jar:

-libraryjars <java.home>/lib/rt.jar(java/**,javax/**)

The filter makes ProGuard disregard com.sun.** classes, for instance , which don't affect the processing of ordinary applications.

It is also possible to filter the jars (and/or wars, ears, zips) themselves, based on their names. For example:

-injars  in(**/acme_*.jar;)
-outjars out.jar

Note the semi-colon in the filter; the filter in front of it applies to jar names. In this case, only acme_*.jar jars are read from the directory in and its subdirectories. Filters for war names, ear names, and zip names can be prefixed with additional semi-colons. All types of filters can be combined. They are orthogonal.

On the other hand, you can also filter the output, in order to control what content goes where. For example:

-injars  in.jar
-outjars code_out.jar(**.class)
-outjars resources_out.jar

This configuration splits the processed output, sending **.class files to code_out.jar, and all remaining files to resources_out.jar.

Again, the filtering can be arbitrarily complex, especially when combined with grouping input and output.

Processing multiple applications at once

You can process several dependent or independent applications (or applets, midlets,...) in one go, in order to save time and effort. ProGuard's input and output handling offers various ways to keep the output nicely structured.

The easiest way is to specify your input jars (and/or wars, ears, zips, and directories) and a single output directory. ProGuard will then reconstruct the input in this directory, using the original jar names. For example, showing just the input and output options:

-injars  application1.jar
-injars  application2.jar
-injars  application3.jar
-outjars processed_applications

After processing, the directory processed_applications will contain processed versions of application jars, with their original names.

Incremental obfuscation

After having processed an application, e.g. ProGuard itself, you can still incrementally add other pieces of code that depend on it, e.g. the ProGuard GUI:
-injars       proguardgui.jar
-outjars      proguardgui_out.jar
-injars       proguard.jar
-outjars      proguard_out.jar
-libraryjars  <java.home>/lib/rt.jar
-applymapping proguard.map

-keep public class proguard.gui.ProGuardGUI {
    public static void main(java.lang.String[]);
}

We're reading both unprocessed jars as input. Their processed contents will go to the respective output jars. The -applymapping option then makes sure the ProGuard part of the code gets the previously produced obfuscation mapping. The final application will consist of the obfuscated ProGuard jar and the additional obfuscated GUI jar.

The added code in this example is straightforward; it doesn't affect the original code. The proguard_out.jar will be identical to the one produced in the initial processing step. If you foresee adding more complex extensions to your code, you should specify the options -useuniqueclassmembernames, -dontshrink, and -dontoptimize in the original processing step. These options ensure that the obfuscated base jar will always remain usable without changes. You can then specify the base jar as a library jar:

-injars       proguardgui.jar
-outjars      proguardgui_out.jar
-libraryjars  proguard.jar
-libraryjars  <java.home>/lib/rt.jar
-applymapping proguard.map

-keep public class proguard.gui.ProGuardGUI {
    public static void main(java.lang.String[]);
}

Preverifying class files for Java Micro Edition

Even if you're not interested in shrinking, optimizing, and obfuscating your midlets, as shown in the midlets example, you can still use ProGuard to preverify the class files for Java Micro Edition. ProGuard produces slightly more compact results than the traditional external preverifier.
-injars      in.jar
-outjars     out.jar
-libraryjars /usr/local/java/wtk2.5.2/lib/midpapi20.jar
-libraryjars /usr/local/java/wtk2.5.2/lib/cldcapi11.jar

-dontshrink
-dontoptimize
-dontobfuscate

-microedition

We're not processing the input, just making sure the class files are preverified by targeting them at Java Micro Edition with the -microedition option. Note that we don't need any -keep options to specify entry points; all class files are simply preverified.

Upgrading class files to Java 6

The following options upgrade class files to Java 6, by updating their internal version numbers and preverifying them. The class files can then be loaded more efficiently by the Java 6 Virtual Machine.
-injars      in.jar
-outjars     out.jar
-libraryjars <java.home>/lib/rt.jar

-dontshrink
-dontoptimize
-dontobfuscate

-target 1.6

We're not processing the input, just retargeting the class files with the -target option. They will automatically be preverified for Java 6 as a result. Note that we don't need any -keep options to specify entry points; all class files are simply updated and preverified.

Finding dead code

These options list unused classes, fields, and methods in the application mypackage.MyApplication:
-injars      in.jar
-libraryjars <java.home>/lib/rt.jar

-dontoptimize
-dontobfuscate
-dontpreverify
-printusage

-keep public class mypackage.MyApplication {
    public static void main(java.lang.String[]);
}

We're not specifying an output jar, just printing out some results. We're saving some processing time by skipping the other processing steps.

The java compiler inlines primitive constants and String constants (static final fields). ProGuard would therefore list such fields as not being used in the class files that it analyzes, even if they are used in the source files. We can add a -keepclassmembers option that keeps those fields a priori, in order to avoid having them listed:

-keepclassmembers class * {
    static final %                *;
    static final java.lang.String *;
}

Printing out the internal structure of class files

These options print out the internal structure of all class files in the input jar:
-injars in.jar

-dontshrink
-dontoptimize
-dontobfuscate
-dontpreverify

-dump

Note how we don't need to specify the Java run-time jar, because we're not processing the input jar at all.

Using annotations to configure ProGuard

The traditional ProGuard configuration allows to keep a clean separation between the code and the configuration for shrinking, optimization, and obfuscation. However, it is also possible to define specific annotations, and then annotate the code to configure the processing.

You can find a set of such predefined annotations in the directory examples/annotations/lib in the ProGuard distribution. The annotation classes are defined in annotations.jar. The corresponding ProGuard configuration (or meta-configuration, if you prefer) is specified in annotations.pro. With these files, you can start annotating your code. For instance, a java source file Application.java can be annotated as follows:

@KeepApplication
public class Application {
  ....
}

The ProGuard configuration file for the application can then be simplified by leveraging off these annotations:

-injars      in.jar
-outjars     out.jar
-libraryjars <java.home>/lib/rt.jar

-include lib/annotations.pro

The annotations are effectively replacing the application-dependent -keep options. You may still wish to add traditional -keep options for processing native methods, enumerations, serializable classes, and annotations.

The directory examples/annotations contains more examples that illustrate some of the possibilities.


Copyright © 2002-2013 Eric Lafortune.