YAML introduction

YAML stands for Ain’t Markup Language , and new data format for serialization language like toml or ini file format.

These files contain text data arranged in a hierarchical structure.

It supports Scalar types (Integer, strings, float, Boolean, Time) and collection types (array, list).

This course series of posts helps you to get the basics with examples for learning.

Important points:

  • It is case sensitive
  • file extension is .yaml
  • Tabs are not allowed,
  • Some editors allow spaces


  • Lightweight
  • It is very easy and simple to represent the complex mapping
  • Friendly readable and writable
  • Simple to modify with any text editor
  • Suitable for configuration settings
  • Support for major programming languages


  • It is a new format introduced recently, and a learning curve exists.
  • Not much popular other than XML and JSON
  • It is very complex to represent configuration in the hierarchy of data

What is the file extension

yaml files are created with the extension .yaml or .yml. You can use any IDE or text editor to open this file.

All the popular IDEs support the yaml file extension and also provide plugins to validate the yaml file content.

What is the YAML media type?

media or MIME types exist in request headers with Content-Type and accept during data transfer between systems.

According to IANA , there is no official MIME type for YAML document content.

It can be represented using text/yaml or text/x-yaml or application/x-yaml mime types.

When yaml data transfers between client and server, Implementation vendors add MIME-type settings specified in requests and responses across the internet. Generally, we can use the MIME format type - text/yaml.

Content-Type and accept headers in a request object are specified with this format.

Following is the mime type for these documents


and request contains the below value for YAML data sent over the internet.

Content-type : text/yaml

The other possible options are

  • text/yaml
  • text/yml
  • text/x-yaml
  • application/yaml
  • application/yml

One of the above is considered based on the browser and the supported programming language.

For example, Chrome accepts application/yaml.

How do you open yaml files?

These files open in a simple text editor or Integrated Development editors like Visual Studio, Atom Sublime Text, Notepad++, and Intelli IDEA in Windows, UNIX, and MAC OS.

Basic editors provide only the capabilities to read and write without format and validation.

IDEs provide plugins following features.

  • Auto or manual Format of the code
  • Syntax highlights coloring
  • Inline render of this content in HTML view
  • Some plugins provide export to PDF and Documents