JAR files are files the main server executables files used to start a server. Users can choose the JAR file they want to use with their server on the Edit Server page in the JAR File dropdown.
The JAR file list is prepopulated with JAR files added by admins.
In case you can’t find the JAR file you are looking for, you can add a custom JAR file to the list by uploading a .jar file to the home directory of your server using the file manager or FTP. After you have uploaded the file, it will appear in the JAR File dropdown.