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Welcome to Apache Joshua

Joshua is a statistical machine translation toolkit for both phrase-based (new in version 6.0) and syntax-based decoding. It can be run with pre-built language packs available for download, and can also be used to build models for new language pairs. Among the many features of Joshua are:

The latest release of Joshua is always linked to directly from the Home Page

New in 6.X

Joshua 6.X includes the following new features:

Quick start

Joshua must be run with a Java JDK 1.8 minimum.

To run the decoder in any form requires setting a few basic environment variables: $JAVA_HOME, $JOSHUA, and, for certain (optional) portions of the model-training pipeline, potentially $MOSES.

export JAVA_HOME=/path/to/java  # maybe /usr/java/home
export JOSHUA=/path/to/joshua

You might also find it helpful to set these:

export LC_ALL=en_US.UTF-8
export LANG=en_US.UTF-8

Then, compile Joshua by typing:

mvn clean package

You also need to download and compile KenLM and Thrax:

bash ./

The basic method for invoking the decoder looks like this:

cat SOURCE | $JOSHUA/bin/joshua-decoder -m MEM -c CONFIG OPTIONS > OUTPUT

Some example usage scenarios and scripts can be found in the examples/ directory.

Development With Eclipse

If you are hoping to work on the decoder, we suggest you use Eclipse. You can get started with this by typing

mvn eclipse:eclipse

Working with "language packs"

Joshua includes a number of "language packs", which are pre-built models that allow you to use the translation system as a black box, without worrying too much about how machine translation works. You can browse the models available for download on the Joshua website.

Building new models

Joshua includes a pipeline script that allows you to build new models, provided you have training data. This pipeline can be run (more or less) by invoking a single command, which handles data preparation, alignment, phrase-table or grammar construction, and tuning of the model parameters. See the documentation for a walkthrough and more information about the many available options.


Joshua is licensed and released under the permissive Apache License v2.0, a copy of which ships with the Joshua source code.