Why spring boot generates jar or war file with .original extension?

The answer is that you are using repackage goal in your spring-boot-maven-plugin. So, What it does?

Maven first builds your project and packages your classes and resources into a WAR (${artifactId}.war) file.

Then, repackaging happens. In this goal, all the dependencies mentioned in the pom.xml are packaged inside a new WAR (${artifactId}.war) and the previously generated war is renamed to ${artifactId}.war.original.

I assume that you're using the spring boot maven build plugin. This behavior is documented here: https://docs.spring.io/spring-boot/docs/current/reference/html/build-tool-plugins-maven-plugin.html