Editing YAML (section)

{{short description|Human-readable data serialization format}}
{{for|the CSS framework|YAML (framework)}}

{{Infobox file format
| name          = YAML
| icon          = Official YAML Logo.svg
| iconcaption   = 
| icon_size     = 
| screenshot    = 
| screenshot_size = 
| caption       = 
| _noextcode    = on
| extensions    = {{code|.yaml}}, {{code|.yml}}
| _nomimecode   = on
| mime          = {{code|application/yaml}}<ref name="rfc9512">{{Cite report |url=https://datatracker.ietf.org/doc/rfc9512/ |title=YAML Media Type |last=Polli |first=Roberto |last2=Wilde |first2=Erik |date=2024-02-21 |publisher=Internet Engineering Task Force |issue=RFC 9512 |last3=Aro |first3=Eemeli |access-date=2024-02-21 |archive-date=2024-02-21 |archive-url=https://web.archive.org/web/20240221185855/https://datatracker.ietf.org/doc/rfc9512/ |url-status=live }}</ref>
| type_code     = 
| uniform_type  = public.yaml<ref>{{cite web |url=https://developer.apple.com/documentation/uniformtypeidentifiers/uttype/3551604-yaml |title=yaml |work=Apple Developer Documentation: Uniform Type Identifiers |publisher=[[Apple Inc]] |access-date=2023-05-22 |archive-date=2023-05-22 |archive-url=https://web.archive.org/web/20230522155815/https://developer.apple.com/documentation/uniformtypeidentifiers/uttype/3551604-yaml |url-status=live }}</ref>
| conforms_to   = 
| magic         = 
| developer     = 
| released      = {{start date and age|2001|05|11|df=yes}}
| latest_release_version = 1.2 (Revision 1.2.2)
| latest_release_date = {{start date and age|2021|10|01|df=yes}}
| genre         = Data interchange
| container_for = 
| extended_from = 
| extended_to   = 
| standard      = <!-- or: | standards = -->
| open          = Yes
| url           = {{URL|https://yaml.org}}
}}

'''YAML''' ({{IPAc-en|'|j|æ|m|ə|l|audio=en-us-YAML.oga}} {{respell|YAM|uhl}}) is a [[human-readable]] [[data serialization language]]. It is commonly used for [[configuration file]]s and in applications where data is being stored or transmitted. YAML targets many of the same communications applications as [[Extensible Markup Language]] (XML) but has a minimal syntax that intentionally differs from [[Standard Generalized Markup Language]] (SGML).<ref name="1.0" /> It uses [[Python (programming language)|Python]]-style indentation to indicate nesting<ref name="1.0">{{cite web|url=https://yaml.org/spec/history/2001-12-10.html|title=Yet Another Markup Language (YAML) 1.0 / Working Draft|date=10 Dec 2001|access-date=2019-05-28|archive-date=2019-07-10|archive-url=https://web.archive.org/web/20190710131145/https://yaml.org/spec/history/2001-12-10.html|url-status=live}}</ref> and does not require quotes around most string values (it also supports [[JSON]] style {{code|[...]}} and <code>{...}</code> mixed in the same file).<ref name="YAML Version 1.2">{{cite web|url=https://yaml.org/spec/1.2/spec.html|title=YAML Ain't Markup Language (YAML) Version 1.2|website=YAML.org|access-date=2019-05-29|archive-date=2019-01-24|archive-url=https://web.archive.org/web/20190124222648/https://yaml.org/spec/1.2/spec.html|url-status=live}}</ref>

Custom data types are allowed, but YAML natively encodes [[Scalar (computing)|scalars]] (such as [[String (computer science)|strings]], [[Integer (computer science)|integers]], and [[Floating point|floats]]), [[List (computing)|lists]], and [[associative arrays]] (also known as maps, dictionaries or hashes). These data types are based on the [[Perl]] programming language, though all commonly used high-level programming languages share very similar concepts.<ref>{{Cite web|title=Built-in Types — Python 3.9.6 documentation|url=https://docs.python.org/3/library/stdtypes.html|access-date=2021-08-19|website=docs.python.org|archive-date=2020-06-14|archive-url=https://web.archive.org/web/20200614194325/https://docs.python.org/3/library/stdtypes.html|url-status=live}}</ref><ref>{{Cite web|title=Standard built-in objects - JavaScript {{!}} MDN|url=https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects|access-date=2021-08-19|website=developer.mozilla.org|language=en-US|archive-date=2021-01-19|archive-url=https://web.archive.org/web/20210119075018/https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects|url-status=live}}</ref><ref>{{Cite web|last=corob-msft|title=Built-in types (C++)|url=https://docs.microsoft.com/en-us/cpp/cpp/fundamental-types-cpp|access-date=2021-08-19|website=docs.microsoft.com|date=17 August 2021|language=en-us|archive-date=2024-06-13|archive-url=https://web.archive.org/web/20240613135924/https://learn.microsoft.com/en-us/cpp/cpp/fundamental-types-cpp?view=msvc-170|url-status=live}}</ref> The colon-centered syntax, used for expressing [[Attribute–value pair|key-value pair]]s, is inspired by [[electronic mail]] headers as defined in {{IETF RFC|0822}}, and the [[Delimiter|document separator]] {{code|---}} is borrowed from [[MIME]] ({{IETF RFC|2046}}). [[Escape sequences]] are reused from [[C (programming language)|C]], and whitespace wrapping for multi-line strings is inspired by [[HTML]]. Lists and hashes can contain nested lists and hashes, forming a [[tree structure]]; arbitrary [[Graph (abstract data type)|graphs]] can be represented using YAML aliases (similar to XML in [[SOAP]]).<ref name="1.0" /> YAML is intended to be read and written in streams, a feature inspired by [[Simple API for XML|SAX]].<ref name="1.0" />

Support for reading and writing YAML is available for many programming languages.<ref>{{Cite web|url=https://yaml.org/|title=The Official YAML Web Site|website=yaml.org|access-date=2019-02-05|archive-date=2021-03-18|archive-url=https://web.archive.org/web/20210318102345/https://yaml.org/|url-status=live}}</ref> Some source-code editors such as [[Vim (text editor)|Vim]],<ref>{{cite web|url=https://www.arthurkoziel.com/setting-up-vim-for-yaml/|title=Setting up Vim for YAML editing|website=arthurkoziel.com|access-date=2021-12-20|archive-date=2021-11-23|archive-url=https://web.archive.org/web/20211123022602/https://www.arthurkoziel.com/setting-up-vim-for-yaml/|url-status=live}}</ref> [[Emacs]],<ref>{{cite web |url=https://www.emacswiki.org/emacs/YamlMode |title=Yaml Mode |publisher=EmacsWiki |date=2015-06-12 |access-date=2016-12-05 |archive-date=2016-11-08 |archive-url=https://web.archive.org/web/20161108052715/https://www.emacswiki.org/emacs/YamlMode |url-status=live }}</ref> and various [[integrated development environment]]s<ref>{{cite web |author=aukaost |url=https://packagecontrol.io/packages/Pretty%20YAML |title=Pretty YAML - Packages - Package Control |publisher=Packagecontrol.io |access-date=2016-12-05 |archive-date=2016-11-08 |archive-url=https://web.archive.org/web/20161108052511/https://packagecontrol.io/packages/Pretty%20YAML |url-status=live }}</ref><ref>{{cite web |url=https://marketplace.eclipse.org/category/free-tagging/yaml |title=yaml &#124; Eclipse Plugins, Bundles and Products - Eclipse Marketplace |publisher=Marketplace.eclipse.org |access-date=2016-12-05 |archive-date=2016-11-08 |archive-url=https://web.archive.org/web/20161108133326/https://marketplace.eclipse.org/category/free-tagging/yaml |url-status=live }}</ref><ref>{{cite web |author=Ruth Kusterer |url=https://netbeans.org/features/ruby/index.html |title=NetBeans IDE - Ruby and Ruby on Rails Development |publisher=Netbeans.org |access-date=2016-12-05 |archive-date=2016-11-19 |archive-url=https://web.archive.org/web/20161119003539/https://netbeans.org/features/ruby/index.html |url-status=dead }}</ref> have features that make editing YAML easier, such as folding up nested structures or automatically highlighting syntax errors.

The official recommended [[filename extension]] for YAML files has been {{code|.yaml}} since 2006.<ref>{{Cite web|url=https://yaml.org/faq.html|title=YAML Ain't Markup Language|date=September 24, 2006|archive-url=https://web.archive.org/web/20060924190202/https://yaml.org/faq.html|archive-date=2006-09-24|url-status=live}}</ref> In 2024, the [[MIME type]] {{code|application/yaml}} has been finalized.<ref name="rfc9512"/>