Difference between .yml and .properties file in Java SpringBoot

In Spring Boot applications, configuration files are used to define application-level settings such as server port, database credentials, logging levels, and environment-specific properties. Spring Boot supports two primary configuration formats:

application.yml

application.yml uses YAML (Yet Another Markup Language), which supports hierarchical and structured configuration. It is more readable when dealing with complex configurations.

Example:

server:
  port: 8080

spring:
  datasource:
    url: jdbc:mysql://localhost:3306/testdb
    username: root
    password: admin

2. .properties File

application.properties uses a simple key–value pair format to configure Spring Boot applications. It is easy to understand and commonly used for small or simple configurations.

Example:

server.port=8080
spring.datasource.url=jdbc:mysql://localhost:3306/testdb
spring.datasource.username=root
spring.datasource.password=admin

Which One Should You Use?

Use .yml When:

• You need hierarchical configurations.
• Your application has complex nested structures.
• You want cleaner and shorter config files.
• Config files are shared across multiple languages or tools.

Use .properties When:

• You prefer simplicity.
• Your configuration is flat and minimal.
• You rely on @PropertySource.
• You want maximum compatibility with legacy Java tools.

application.yml vs application.properties