What is YAML

Originally YAML was said to mean Yet Another Markup Language, referencing its purpose as a markup language with the yet another construct, but it was then repurposed as YAML Ain't Markup Language, a recursive acronym, to distinguish its purpose as data-oriented, rather than document markup.

Below is an example of an invoice expressed via YAML(tm). Structure is shown through indentation (one or more spaces). Sequence items are denoted by a dash, and key value pairs within a map are separated by a colon.

invoice: 34843
date   : 2001-01-23
bill-to: &id001
    given  : John
    family : Smith
    address:
        lines: |
            458 Walkman Dr.
            Suite #292
        city    : Mumbai
        state   : MH
        postal  : 48046
ship-to: *id001
product:
    - sku         : BL394D
      quantity    : 4
      description : Basketball
      price       : 450.00
    - sku         : BL4438H
      quantity    : 1
      description : Super Hoop
      price       : 2392.00
tax  : 251.42
total: 4443.52
comments: >
    Late afternoon is best.
    Backup contact is Nancy
    Billsmer @ 338-4338.

The official recommended filename extension for YAML files has been .yaml since 2006.