noun

YAML

YAM-uhl

YAML (noun) means a plain-text format for writing structured data — lists, settings and named values — designed to be easy for people to read and edit. Instead of brackets, it uses line breaks, dashes and indentation to show how items relate to one another. It stores information; it does not give instructions, so it is not a programming language. Example: “The whole deployment is configured in a single YAML file.”

noun

technical, computing A plain-text format for writing structured data — lists, settings and named values — designed to be easy for people to read and edit. Instead of brackets, it uses line breaks, dashes and indentation to show how items relate to one another. It stores information; it does not give instructions, so it is not a programming language.

"The whole deployment is configured in a single YAML file."

"One stray tab broke the YAML and the build refused to start."

technical, computing A file written in that format, usually ending in .yaml or .yml.

"Have a look at the YAML in the root of the repository."

How to Use YAML

Learner’s notes

In plain EnglishA tidy way of writing settings and lists in a text file so people can read them easily.

When to use it

Technical, very common in software configuration and deployment.

Memory tip

Rhymes with camel. Say "YAM-ul", not "why-AY-em-el".

Trace the full origin ↓

Easily confused with

JSON → TOML XML → INI

Common pairings

YAML file YAML config valid YAML YAML syntax parse YAML

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Fill the Gap

Can you complete this real example?

The whole deployment is configured in a single _____ file.

Etymology

A recursive acronym for YAML Ain't Markup Language; it originally stood for Yet Another Markup Language.

Origin: English

Synonyms

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data serialisation format configuration format config format markup-style data format YAML file config file

Frequently Asked Questions

What is the difference between YAML and JSON?

Both describe the same kinds of structured data, but JSON uses braces, brackets and quotation marks, while YAML uses indentation and dashes and needs far less punctuation. YAML is easier for a person to read and allows comments; JSON is stricter and simpler for machines to handle. YAML is designed so that valid JSON is also valid YAML.

Why does indentation matter so much in YAML?

Because indentation is how YAML shows which items belong inside which. Moving a line in or out by a space changes its meaning, and the format forbids tab characters for indenting, so mixing tabs and spaces is a common cause of errors.

Is .yml the same as .yaml?

Yes, they are the same format under two extensions. The three-letter .yml survives from systems that expected short extensions; the project's own recommendation is .yaml. Most tools accept either.