Yml is more concise and intuitive than properties configuration file.
It is more convenient if application.yml is used as the default format of the spring boot project configuration file.
Comment From: snicoll
Every time I create the spring boot project, I have to modify it application.properties format
I am assuming you are referring to start.spring.io and therefore this is the wrong issue tracker to discuss this. We've already discussed this in several occasions, see this issue in the start.spring.io project issue tracker