A Properties file in Java is a list of key-value pairs that can be parsed by java.util.Properties class.

Generally a Properties file has extension .properties e.g. myapp.properties.

Properties files are used for many purposes in all kinds of Java applications. Some of the uses are to store configuration, initial data, application options etc.

When we change the value of a key in a properties file, there is no need to recompile the Java application. So it provides benefit of changing values at runtime.