What is WAR file?
WAR files are Java Web Archive files that allow Java to store data in a self-contained archive. They are also used to build web applications with Java. The WAR file format was originally developed by Sun Microsystems between 1997 and 1999 while it was still using the name of "Java Archive" for its file extension. It is now known as the WAR File Extension while being open sourced on GitHub in August 2013. Since this is an introduction, I will not include any content on this particular topic.
WAR Format details
|Java Web Archive
Software, that convert WAR files
The easiest way to convert a WAR file is to save it in a different file format using dedicated software. Below you will find a list of software programs that can handle WAR files. Open your WAR file with one of them and save in another file format.