.YML File Extension

File created in the YAML (YAML Ain't Markup Language) format, a human-readable data format used for data serialization; allows data to be written and read independent of any particular language; can be incorporated into many different programming languages using supporting YAML libraries, including C/C++, Ruby, Python, Java, Perl, C#, PHP, and others.

One example of YAML usage is the database.yml file, which is used by Ruby on Rails to save connection information when connecting to a database.