OmegaT comes in two editions:
This edition is recommended for everyday use.
This edition is automatically generated every time new code is added to OmegaT. It is used for testing purposes.
The files are downloadable directly from https://omegat.org.
OmegaT OmegaT 6.0.1 requires a Java 11 Runtime Environment (JRE) to run.
OmegaT packages are available both in versions bundled with Java, and versions without it. Packages without Java rely on a Java 11 Runtime Environment installed systemwide.
OmegaT OmegaT 6.0.1 and later also support Java 11 Runtime Environment on any platforms.
Due to licensing considerations, the OmegaT team recommends the Java runtime Eclipse Temurin provided by the Eclipse Foundation's Adoptium Project, but any Java 11 compatible runtime environment should work.
Double-click on the package you downloaded.
You can choose the language used during the installation and the
            language used by OmegaT. You can also change this later by editing
            OmegaT.l4J.ini.
          
Some Linux distributions offer OmegaT in their package manager. The instructions given here apply to people who download the package from the https://omegat.org site and install it manually.
Unpack/untar the file you downloaded. This creates a new folder named after the package you downloaded. That folder contains all the files needed to run OmegaT.
Although you can run OmegaT directly from the available
          files, you can also run the linux-install.sh
          script found there to have OmegaT installed in more appropriate
          locations.
Running the script will require you to enter your
          sudo password.
        
The script checks for an existing installation of the same
          OmegaT version in /opt/omegat/. If there isn’t
          one, it installs the program in
          /opt/omegat/OmegaT_OmegaT 6.0.1 and sets it as the
          default version (in
          /opt/omegat/OmegaT-default).
        
After the unpacking or installation is complete, you can delete the downloaded file as it is no longer needed.
Double click on the package you downloaded to unpack it. This
            creates a folder called OmegaT. The folder contains
            two files: index.html (the user guide index) and
            OmegaT.app (the application). Copy the folder to a
            suitable location (e.g. Applications).
      
Eventually, drag and drop OmegaT.app onto the
        Dock to easily access it.
Once you have done this, you can delete the downloaded file as it is no longer needed.
This information applies to all systems that have a Java version compatible with Java 11 Runtime Environment. That includes the platforms described above, but also the platforms for which specific packages are not provided.
Download the Cross-platform without JRE version.
The Eclipse Foundation provides OpenJDK Runtime Environments JREs for many systems at https://adoptium.net/temurin.
IBM provides JREs for Linux PowerPC at https://developer.ibm.com/languages/java/semeru-runtimes/downloads/.
Follow the installation instructions of the package you need.
Unpack the file that you downloaded. This creates a folder with all the files necessary to run OmegaT.
Follow your system’s instructions to install OmegaT shortcuts in convenient places of your choosing.
The changes between your version and the current version are documented in the development site’s changes.txt file.
If you decide to install a new version, keep the following in mind:
OmegaT’s preferences are stored in the configuration folder and will not be modified by the new version.
Projects that you have created in the past or are currently using will not be modified or deleted. OmegaT projects are not stored inside OmegaT. They are separate objects that have no physical connection to the OmegaT application itself.
Parameter files that are included in the downloaded OmegaT
                package (especially the OmegaT.l4J.ini for Windows and the
                Configuration.properties and
                Info.plist files for macOS packages) might be
                overwritten or deleted, so you may want to create a backup before
                upgrading, if you have been using these files to modify OmegaT’s
                launch parameters.
              
The plugins and
                scripts folders might be overwritten, so you
                may want to create a backup before upgrading.
              
To do this, simply select the same installation folder as the existing installation when installing the new version. The “old” version of OmegaT will be overwritten, but settings made from the OmegaT interface will be retained in the various configurations folders (see above).
This will enable you to keep any number of versions side-by-side, which you may wish to do until you feel comfortable with the new version.
All the parameters located in the Configuration Folder will
              be shared unless you specify a different configuration folder with the
              --config-dir=<path> option from the OmegaT
              options on the
              command line . All the parameters located in a Project Folder will apply to
              that project regardless of which version of OmegaT opens it.