HKXPack version 0.1.4-beta

HKXPack is a tool to 'pack' and 'unpack' to and from hkx files, which is the Havok compressed file format.

It was made to be used with the hk_2014.1.0-r1 file format, commonly used in Fallout 4. Given the opportunity, support for hk_2010.2.0-r1 or other hkx formats may be added.

The output format is intended to be TagXML, output by figment's hkxcmd.

Some other output formats may be added in the future (e.g. XAF/XMM or FBX for animations), but these formats aren't the focus of the tool. Note : this behavior now has been moved to the HKXAnim repository.


You can download the latest release here.

How to

To use this tool, you will need a Java Runtime Environement (jre) for Java 8 or higher.

Don't forget to put quotes around your path if you have a path with spaces !

Unpack the files

Use the command java -jar hkxpack-cli.jar unpack <filename>.hkx to extract the file into <filename>.xml.

You can also use java -jar hkxpack-cli.jar unpack <directory> to extract the directory's HKX files into XML files, under the out/ folder

Pack the files

Use the command java -jar hkxpack-cli.jar pack <filename>.xml to pack the file into <filename>.hkx.

You can also use java -jar hkxpack-cli.jar pack <directory> to extract the directory's XML files into HKX files, under the out/ folder


Common options are :

Advanced options are :

Known bugs



This project can be built using Maven. Use the command by running the following Maven goals mvn clean package. The compiled jar will then be available under /cli/target/hkxpack-cli.jar


Import this project as a standard Maven project.

Contribution rules

See for a list of contribution rules.

General information

The tool was written for Java 8 using the Oracle JavaSE JDK (jdk1.8.0_66), and was originally intended to be a proof of concept.

You may find all available information under /doc. It contains mostly analysis and comparison of the hkx files as well as some software architecture concepts of the hkxpack software.

You might find out that some of the data required to run the tool is missing. That's because the 'classXML' files are obtained from the Fallout 4 game. You'll need the game to retrieve the files and, to prevent possible legal issues, they're not included in the sources. The way to obtain these files is currently built specifically for one machine, and its distribution isn't a priority.


MIT, See the LICENSE file.


Thanks to Aerisam for his help understanding the animation data.
Thanks to CPU for his overall help with making this project.
Thanks to Figment for his help to obtain information about the hkx classes. Without him, none of this would be possible.
Thanks to Fore for his FNIS tool that allowed slight modifications of old files, and for sharing his knowledge of behaviours with me.
Thanks to Neomonkeus for making the Maven integration.
Thanks to Orvid for his advice about how to make both working and clean code.
Thanks to Philjord for adapting data handling from files to buffers.
Thanks to the people from the NifTools IRC for helping with making this project and their overall support.