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Packages your JAR, assets and a JVM for distribution on Windows, Linux and Mac OS X
C++ C Java Other
branch: master

Merge pull request #37 from libgdx/jrenner-patch-1

prevent packr from deleting root directory
latest commit 77fd9c0e1f
David Saltares siondream authored


Packages your JAR, assets and a JVM for distribution on Windows (ZIP), Linux (ZIP) and Mac OS X (.app), adding a native executable file to make it appear like the app is a native app. Packr is most suitable for GUI applications, such as games made with libGDX

Download Packr


You point packr at your JAR file (containing all your code and assets), a JSON config file (specifying parameters to the JVM and the main class) and a URL or local file location to an OpenJDK build for the platform you want to build. Invoking packr from the command line may look like this:

java -jar packr.jar \
     -platform mac \
     -jdk "" \
     -executable myapp \
     -appjar myapp.jar \
     -mainclass "com/my/app/MainClass" \
     -vmargs "-Xmx1G" \
     -resources pom.xml;src/main/resources \
     -minimizejre "soft" \
     -outdir out
Parameter Meaning
platform one of "windows", "linux32", "linux64", "mac"
jdk ZIP file location or URL to an OpenJDK build containing a JRE. Prebuild JDKs can be found at
executable name of the native executable, without extension such as ".exe"
appjar file location of the JAR to package
mainclass the fully qualified name of the main class, using forward slashes to delimit package names
vmargs list of arguments for the JVM, separated by ;, e.g. "-Xmx1G"
outdir output directory
resources (optional) list of files and directories to be packaged next to the native executable, separated by ;.
minimizejre minimize the JRE by removing directories and files as specified by the config file. Comes with two config files out of the box called "soft" and "hard". See below for details on the minimization config file.

Alternatively, you can put all the command line arguments into a JSON file which might look like this:


    "platform": "mac",
    "jdk": "/Users/badlogic/Downloads/",
    "executable": "myapp",
    "appjar": "myapp.jar",
    "mainclass": "com/my/app/MainClass",
    "vmargs": [
    "resources": [
    "minimizejre": "soft",
    "outdir": "out-mac"

You can then invoke the tool like this:

java -jar packr.jar my-packaging-config.json

Finally, you can use packr from within your code. Just add the JAR file to your project, either manually, or via the following Maven dependency:


To invoke packr, you need to create an instance of Config and pass it to Packr#pack()

Config config = new Config();
config.platform =;
config.jdk = "/User/badlogic/Downloads/";
config.executable = "myapp";
config.jar = "myjar.jar";
config.mainClass = "com/my/app/MainClass";
config.vmArgs = Arrays.asList("-Xmx1G");
config.minimizeJre = new String[] { "jre/lib/rt/com/sun/corba", "jre/lib/rt/com/sun/jndi" };
config.outDir = "out-mac";

new Packr().pack(config)


A standard JRE weighs about 90mb unpacked and about 50mb packed. Packr helps you cut down on that size, thus also reducing the download size of your app.

To minimize the JRE that is bundled with your app, you have to specify a minimization configuration file via the minimizejre flag you supply to Packr. Such a minimization configuration contains the names of files and directories within the JRE to be removed, one per line in the file. E.g.:


This will remove the rhino.jar (about 1.1MB) and all the packages and classes in com.sun.corba from the rt.jar file. To specify files and packages to be removed from the JRE, simply prepend them with jre/lib/rt/.

Packr comes with two such configurations out of the box, soft and hard

Additionally, Packr will compress the rt.jar file. By default, the JRE uses zero-compression on the rt.jar file to make application startup a little faster.


When packing for Windows, the following folder structure will be generated




Mac OS X


You can futher modify the Info.plist to your liking, e.g. add icons, a bundle identifier etc. If your outdir has the .app extension it will be treated as an application bundle by Mac OS X.


If you only modify the Java code, it's sufficient to invoke Maven

mvn clean package

This will create a packr-VERSION.jar file in target which you can invoke as described in the Usage section above.

If you want to compile the exe files used by packr, install premake, Visual Studio 2010 Express on Windows, Xcode on Mac OS X and GCC on Linux, then invoke the build-xxx scripts in the natives/ folder. Each script will create an executable file for the specific platform and place it under src/main/resources.


  • Icons aren't set yet on any platform, need to do that manually.
  • Windows is 32-bit only, Mac OS X is 64-bit only
  • JRE minimization is very conservative, depending on your app, you can carve out stuff from a JRE yourself, disable minimization and pass your custom JRE to packr

Code Warning

You may find some style issues with this code, namely:

  • lack of proper logging
  • lack of return value checking

This was conceived over a "weekend" so to speak, so please excuse any shortcomings. Happy to receive PRs!

License & Contributions

The code is licensed under the Apache 2 license. By contributing to this repository, you automatically agree that your contribution can be distributed under the Apache 2 license by the author of this project. You will not be able to revoke this right once your contribution has been merged into this repository.


Distributing a bundled JVM has security implications, just like bundling any other runtimes like Mono, Air, etc. Make sure you understand the implications before deciding to use this tool. Here's a discussion on the topic.

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