A lightweight markup language (LML), also termed a simple or humane markup language, is a markup language with simple, unobtrusive syntax. It is designed to be easy to write using any generic text editor and easy to read in its raw form. Lightweight markup languages are used in applications where it may be necessary to read the raw document as well as the final rendered output.

For instance, a person downloading a software library might prefer to read the documentation in a text editor rather than a web browser. Another application for such languages is to provide for data entry in web-based publishing, such as blogs and wikis, where the input interface is a simple text box. The server software then converts the input into a common document markup language like HTML.

History

Lightweight markup languages were originally used on text-only displays which could not display characters in italics or bold, so informal methods to convey this information had to be developed. This formatting choice was naturally carried forth to plain-text email communications. Console browsers may also resort to similar display conventions.

In 1986 international standard SGML provided facilities to define and parse lightweight markup languages using grammars and tag implication. The 1998 W3C XML is a profile of SGML that omits these facilities. However, no SGML document type definition (DTD) for any of the languages listed below is known.

Types

Lightweight markup languages can be categorized by their tag types. Like HTML (<b>bold</b>), some languages use named elements that share a common format for start and end tags (e.g. BBCode [b]bold[/b]), whereas proper lightweight markup languages are restricted to ASCII-only punctuation marks and other non-letter symbols for tags, but some also mix both styles (e.g. Textile bq. ) or allow embedded HTML (e.g. Markdown), possibly extended with custom elements (e.g. MediaWiki <ref>'''source'''</ref>).

Most languages distinguish between markup for lines or blocks and for shorter spans of texts, but some only support inline markup.

Some markup languages are tailored for a specific purpose, such as documenting computer code (e.g. POD, reST, RD) or being converted to a certain output format (usually HTML or LaTeX) and nothing else, others are more general in application. This includes whether they are oriented on textual presentation or on data serialization.[clarification needed]

Presentation oriented languages include AsciiDoc, atx, BBCode, Creole, Crossmark, Djot, Epytext, Haml, JsonML, MakeDoc, Markdown, Org-mode, POD (Perl), reST (Python), RD (Ruby), Setext, SiSU, SPIP, Xupl, Texy!, Textile, txt2tags, UDO and Wikitext.

Data serialization oriented languages include Curl (homoiconic, but also reads JSON; every object serializes), JSON, and YAML.

Comparison of language features

More information Language, HTML export tool ...
Comparing language features
Language HTML export tool HTML import tool Tables Link titles class attribute id attribute Release date
AsciiDoc Yes Yes Yes Yes Yes Yes 2002-11-25[1]
BBCode No No Yes No No No 1998
Creole No No Yes No No No 2007-07-04[2]
Djot Yes Yes[3] Yes Yes Yes Yes 2022-07-30[4]
Gemtext Yes  ? No Yes No No 2020
GitHub Flavored Markdown Yes No Yes Yes No No 2011-04-28+
Jira Formatting Notation Yes No Yes Yes No No 2002+[5]
Markdown Yes Yes No Yes Yes/No Yes/No 2004-03-19[6][7]
Markdown Extra Yes Yes Yes[8] Yes Yes Yes 2013-04-11[9]
MediaWiki Yes Yes Yes Yes Yes Yes 2002[10]
MultiMarkdown Yes No Yes Yes No No 2009-07-13
Org-mode Yes Yes[11] Yes Yes Yes Yes 2003[12]
PmWiki Yes[13] Yes Yes Yes Yes Yes 2002-01
POD Yes  ? No Yes  ?  ? 1994
reStructuredText Yes Yes[11] Yes Yes Yes auto 2002-04-02[14]
setext Yes Yes No Yes No No 1992[15]
Slack No No No Yes No No 2013+[16][17]
TiddlyWiki Yes No Yes Yes Yes No 2004-09[18]
Textile Yes No Yes Yes Yes Yes 2002-12-26[19]
Texy Yes Yes Yes Yes Yes Yes 2004[20]
txt2tags Yes Yes[21] Yes[22] Yes Yes/No Yes/No 2001-07-26[23]
WhatsApp No No No No No No 2016-03-16[24]
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Markdown's own syntax does not support class attributes or id attributes; however, since Markdown supports the inclusion of native HTML code, these features can be implemented using direct HTML. (Some extensions may support these features.)

txt2tags' own syntax does not support class attributes or id attributes; however, since txt2tags supports inclusion of native HTML code in tagged areas, these features can be implemented using direct HTML when saving to an HTML target.[25]

Comparison of implementation features

More information Language, Implementations ...
Comparing implementations, especially output formats
LanguageImplementations XHTMLCon/LaTeXPDFDocBookODFEPUBDOC(X) LMLsOther License
AsciiDoc Python, Ruby, JavaScript, Java XHTMLLaTeXPDFDocBookODFEPUBNo Man page etc. GNU GPL, MIT
BBCode Perl, PHP, C#, Python, Ruby (X)HTMLNoNoNoNoNoNo Public Domain
Creole PHP, Python, Ruby, JavaScript[26] Depends on implementation CC_BY-SA 1.0
Djot Lua (originally), JavaScript, Prolog, Rust[3] HTMLLaTeX, ConTeXtPDFDocBookODFEPUBRTF MediaWiki, reSTMan page, S5 etc. MIT
GitHub Flavored Markdown Haskell (Pandoc) HTMLLaTeX, ConTeXtPDFDocBookODFEPUBDOC AsciiDoc, reSTOPML GPL
Java,[27] JavaScript,[28][29][30] PHP,[31][32] Python,[33] Ruby[34] HTML[28][29][30][32][33]NoNoNoNoNoNo Proprietary
Markdown Perl (originally), C,[35][36] Python,[37] JavaScript, Haskell,[11] Ruby,[38] C#, Java, PHP HTMLLaTeX, ConTeXtPDFDocBookODFEPUBRTF MediaWiki, reSTMan page, S5 etc. BSD-style & GPL (both)
Markdown Extra PHP (originally), Python, Ruby XHTMLNoNoNoNoNoNo BSD-style & GPL (both)
MediaWiki Perl, PHP, Haskell, Python XHTMLNoNoNoNoNoNo GNU GPL
MultiMarkdown C, Perl (X)HTMLLaTeXPDFNoODFNoDOC, RTF OPML GPL, MIT
Org-mode Emacs Lisp, Ruby (parser only), Perl, OCaml XHTMLLaTeXPDFDocBookODFEPUB[39]DOCX[39] MarkdownTXT, XOXO, iCalendar, Texinfo, man, contrib: groff, s5, deck.js, Confluence Wiki Markup,[40] TaskJuggler, RSS, FreeMind GPL
PmWiki PHP XHTML 1.0 Transitional, HTML5NoPDF export addonsNoNoEPUB export addonNo GNU GPL
POD Perl (X)HTML, XMLLaTeXPDFDocBookNoNoRTF Man page, plain text Artistic License, Perl's license
reStructuredText Python,[41][42] Haskell (Pandoc), Java, HTML, XMLLaTeXPDFDocBookODFEPUBDOC man, S5, Devhelp, QT Help, CHM, JSON Public Domain
Textile PHP, JavaScript, Java, Perl, Python, Ruby, ASP, C#, Haskell XHTMLNoNoNoNoNoNo Textile License
Texy! PHP, C# (X)HTMLNoNoNoNoNoNo GNU GPL v2 License
txt2tags Python,[43] PHP[44] (X)HTML, SGMLLaTeXPDFDocBookODFEPUBDOCCreole, AsciiDoc, MediaWiki, MoinMoin, PmWiki, DokuWiki, Google Code Wikiroff, man, MagicPoint, Lout, PageMaker, ASCII Art, TXT GPL
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Comparison of lightweight markup language syntax

Inline span syntax

Although usually documented as yielding italic and bold text, most lightweight markup processors output semantic HTML elements em and strong instead. Monospaced text may either result in semantic code or presentational tt elements. Few languages make a distinction, e.g. Textile, or allow the user to configure the output easily, e.g. Texy.

LMLs sometimes differ for multi-word markup where some require the markup characters to replace the inter-word spaces (infix). Some languages require a single character as prefix and suffix, other need doubled or even tripled ones or support both with slightly different meaning, e.g. different levels of emphasis.

More information HTML output, <strong>strongly emphasized</strong> ...
Comparison of text formatting syntax
HTML output <strong>strongly emphasized</strong> <em>emphasized text</em> <code>code</code> semantic
<b>bold text</b> <i>italic text</i> <tt>monospace text</tt> presentational
AsciiDoc *bold text* 'italic text' +monospace text+ Can double operators to apply formatting where there is no word boundary (for example **b**old t**ex**t yields bold text).
_italic text_ `monospace text`
BBCode [b]bold text[/b] [i]italic text[/i] [code]monospace text[/code] Formatting works across line breaks.
Creole **bold text** //italic text// {{{monospace text}}} Triple curly braces are for nowiki which is optionally monospace.
Djot *bold text* _italic text_ `monospace text`
Gemtext ```alt text
monospace text
```
Text immediately following the first three backticks is alt-text.
Jira Formatting Notation *bold text* _italic text_ {{monospace text}}
Markdown[45] **bold text** *italic text* `monospace text` semantic HTML tags
__bold text__ _italic text_
MediaWiki '''bold text''' ''italic text'' <code>monospace text</code> mostly resorts to inline HTML
Org-mode *bold text* /italic text/ =code=
~verbatim~
PmWiki '''bold text''' ''italic text'' @@monospace text@@
reST **bold text** *italic text* ``monospace text``
Setext **bold text** ~italic text~ `monospace text`
Textile[46] *strong* _emphasis_ @monospace text@ semantic HTML tags
**bold text** __italic text__ presentational HTML tags
Texy! **bold text** *italic text* `monospace text` semantic HTML tags by default, optional support for presentational tags
//italic text//
TiddlyWiki ''bold text'' //italic text// `monospace text`
``monospace text``
txt2tags **bold text** //italic text// ``monospace text``
POD B<bold text> I<italic text> C<monospace text> Indented text is also shown as monospaced code.
Slack *bold text* _italic text_ `monospace text` ```block of monospaced text```
WhatsApp *bold text* _italic text_ ```monospace text```
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Gemtext does not have any inline formatting, monospaced text (called preformatted text in the context of Gemtext) must have the opening and closing ``` on their own lines.

Emphasis syntax

In HTML, text is emphasized with the <em> and <strong> element types, whereas <i> and <b> traditionally mark up text to be italicized or bold-faced, respectively.

Microsoft Word and Outlook, and accordingly other word processors and mail clients that strive for a similar user experience, support the basic convention of using asterisks for boldface and underscores for italic style. While Word removes the characters, Outlook retains them.

More information AsciiDoc, ATX ...
Italic type or normal emphasis
Code AsciiDocATXCreoleJiraMarkdownMediaWikiOrg-modePmWikireSTSetextSlackTextileTexy!TiddlyWikitxt2tagsWhatsApp
*italic* NoNoNoNoYesNoNoNoYesNoNoNoYesNoNoNo
**italic** NoNoNoNoNoNoNoNoNoNoNoNoNoNoNoNo
_italic_ YesYesNoYesYesNoNoNoNoNoYesYesNoNoNoYes
__italic__ YesNoNoNoNoNoNoNoNoNoNoYesNoNoNoNo
'italic' YesNoNoNoNoNoNoNoNoNoNoNoNoNoNoNo
''italic'' YesNoNoNoNoYesNoYesNoNoNoNoNoNoNoNo
/italic/ NoNoNoNoNoNoYesNoNoNoNoNoNoNoNoNo
//italic// NoNoYesNoNoNoNoNoNoNoNoNoYesYesYesNo
~italic~ NoNoNoNoNoNoNoNoNoYesNoNoNoNoNoNo
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More information AsciiDoc, ATX ...
Bold face or strong emphasis
Code AsciiDocATXCreoleJiraMarkdownMediaWikiOrg-modePmWikireSTSetextSlackTextileTexy!TiddlyWikitxt2tagsWhatsApp
*bold* YesYesNoYesNoNoYesNoNoNoYesYesNoNoNoYes
**bold** YesNoYesNoYesNoNoNoYesYesNoYesYesNoYesNo
__bold__ NoNoNoNoYesNoNoNoNoNoNoNoNoNoNoNo
''bold'' NoNoNoNoNoNoNoNoNoNoNoNoNoYesNoNo
'''bold''' NoNoNoNoNoYesNoYesNoNoNoNoNoNoNoNo
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Editorial syntax

In HTML, removed or deleted and inserted text is marked up with the <del> and <ins> element types, respectively. However, legacy element types <s> or <strike> and <u> are still also available for stricken and underlined spans of text.

More information Jira, Markdown ...
Underlined or inserted text
Code JiraMarkdownOrg-modeSetextTiddlyWikitxt2tags
_underline_ NoOptionalYesYesNoNo
__underline__ NoOptionalNoNoYesYes
+underline+ YesNoNoNoNoNo
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AsciiDoc, ATX, Creole, MediaWiki, PmWiki, reST, Slack, Textile, Texy! and WhatsApp do not support dedicated markup for underlining text. Textile does, however, support insertion via the +inserted+ syntax.

More information Jira, Markdown ...
Strike-through or deleted text
Code JiraMarkdownOrg-modeSlackTextileTiddlyWikitxt2tagsWhatsApp
~stricken~ NoNoNoYesNoNoNoYes
~~stricken~~ NoGFMNoNoNoYesNoNo
+stricken+ NoNoYesNoNoNoNoNo
-stricken- YesNoNoNoYesNoNoNo
--stricken-- NoNoNoNoNoNoYesNo
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AsciiDoc, ATX, Creole, MediaWiki, PmWiki, reST, Setext and Texy! do not support dedicated markup for striking through text.

Programming syntax

Quoted computer code is traditionally presented in typewriter-like fonts where each character occupies the same fixed width. HTML offers the semantic <code> and the deprecated, presentational <tt> element types for this task.

More information AsciiDoc, ATX ...
Monospaced font, teletype text or code
Code AsciiDocATXCreoleGemtextJiraMarkdownOrg-modePmWikireSTSlackTextileTexy!TiddlyWikitxt2tagsWhatsApp
@code@ NoNoNoNoNoNoNoNoNoNoYesNoNoNoNo
@@code@@ NoNoNoNoNoNoNoYesNoNoNoNoNoNoNo
`code` YesNoNoNoNoYesNoNoNoYesNoYesYesNoNo
``code`` YesNoNoNoNoYesNoNoYesNoNoNoYesYesNo
```code``` NoNoNoYesNoYesNoNoNoYes/NoNoNoYesNoYes
=code= NoNoNoNoNoNoYesNoNoNoNoNoNoNoNo
~code~ NoNoNoNoNoNoYesNoNoNoNoNoNoNoNo
+code+ YesNoNoNoNoNoNoNoNoNoNoNoNoNoNo
++code++ YesNoNoNoNoNoNoNoNoNoNoNoNoNoNo
{{code}} NoNoNoNoYesNoNoNoNoNoNoNoNoNoNo
{{{code}}} NoNoYesNoNoNoNoNoNoNoNoNoNoNoNo
|code| NoYesNoNoNoNoNoNoNoNoNoNoNoNoNo
;;code;;
Close

Mediawiki and Gemtext do not provide lightweight markup for inline code spans.

Heading syntax

Headings are usually available in up to six levels, but the top one is often reserved to contain the same as the document title, which may be set externally. Some documentation may associate levels with divisional types, e.g. part, chapter, section, article or paragraph.

Most LMLs follow one of two styles for headings, either Setext-like underlines or atx-like[47] line markers, or they support both.

Underlined headings

Level 1 Heading
===============

Level 2 Heading
---------------

Level 3 Heading
~~~~~~~~~~~~~~~

The first style uses underlines, i.e. repeated characters (e.g. equals =, hyphen - or tilde ~, usually at least two or four times) in the line below the heading text.

More information Chars:, = ...
Underlined heading levels
Chars: = - ~ * # + ^ _ : " ' ` . min length
Markdown 12NoNoNoNoNoNoNoNoNoNoNo1
Setext 12NoNoNoNoNoNoNoNoNoNoNo ?
AsciiDoc 123NoNoNoNoNoNoNoNoNoNo2
Texy! 34No21NoNoNoNoNoNoNoNo3
reStructuredText YesYesYesYesYesYesYesYesYesYesYesYesYesheading width
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RST determines heading levels dynamically, which makes authoring more individual on the one hand, but complicates merges from external sources on the other hand.

Prefixed headings

# Level 1 Heading
## Level 2 Heading ##
### Level 3 Heading ###

The second style is based on repeated markers (e.g. hash #, equals = or asterisk *) at the start of the heading itself, where the number of repetitions indicates the (sometimes inverse) heading level. Most languages also support the reduplication of the markers at the end of the line, but whereas some make them mandatory, others do not even expect their numbers to match.

More information Character:, = ...
Line prefix (and suffix) headings
Character: = # * ! + Suffix Levels Indentation
AsciiDoc YesNoNoNoNo Optional1–6No
Creole YesNoNoNoNo Optional1–6No
Gemtext NoYesNoNoNo  ?1–3No
MediaWiki YesNoNoNoNo Yes1–6No
TiddlyWiki NoNoNoYesNo No1–6No
txt2tags YesNoNoNoYes Yes1–6No
Markdown NoYesNoNoNo Optional1–6No
Texy! YesYesNoNoNo Optional6–1, dynamicNo
Org-mode NoNoYesNoNo No1– +∞alternative[48][49][50]
PmWiki NoNoNoYesNo Optional1–6No
Close

Org-mode supports indentation as a means of indicating the level.

BBCode does not support section headings at all.

POD and Textile choose the HTML convention of numbered heading levels instead.

More information Language, Format ...
Other heading formats
Language Format
POD
=head1 Level 1 Heading
=head2 Level 2 Heading
Textile,[46] Jira[5]
h1. Level 1 Heading
h2. Level 2 Heading
h3. Level 3 Heading
h4. Level 4 Heading
h5. Level 5 Heading
h6. Level 6 Heading
Close

Microsoft Word supports auto-formatting paragraphs as headings if they do not contain more than a handful of words, no period at the end and the user hits the enter key twice. For lower levels, the user may press the tabulator key the according number of times before entering the text, i.e. one through eight tabs for heading levels two through nine.

Hyperlinks can either be added inline, which may clutter the code because of long URLs, or with named alias or numbered id references to lines containing nothing but the address and related attributes and often may be located anywhere in the document. Most languages allow the author to specify text Text to be displayed instead of the plain address http://example.com and some also provide methods to set a different link title Title which may contain more information about the destination.

LMLs that are tailored for special setups, e.g. wikis or code documentation, may automatically generate named anchors (for headings, functions etc.) inside the document, link to related pages (possibly in a different namespace) or provide a textual search for linked keywords.

Most languages employ (double) square or angular brackets to surround links, but hardly any two languages are completely compatible. Many can automatically recognize and parse absolute URLs inside the text without further markup.

More information Languages, Basic syntax ...
Hyperlink syntax
Languages Basic syntaxText syntaxTitle syntax
BBCode, Creole, MediaWiki, PmWiki http://example.com
Textile "Text":http://example.com "Text (Title)":http://example.com
Texy! "Text .(Title)":http://example.com
AsciiDoc http://example.com[Text]
Slack <http://example.com|Text>
TiddlyWiki [[Text|http://example.com]]
Jira [http://example.com] [Text|http://example.com]
txt2tags [Text http://example.com]
MediaWiki [http://example.com Text]
Creole, MediaWiki, PmWiki [[Name]] [[Name|Text]]
Org-mode [[Name][Text]]
TiddlyWiki [[Text|Name]]
Creole [[Namespace:Name]] [[Namespace:Name|Text]]
Org-mode [[Namespace:Name][Text]]
Creole, PmWiki [[http://example.com]] [[http://example.com|Text]]
BBCode [url]http://example.com[/url] [url=http://example.com]Text[/url]
Markdown <http://example.com> [Text](http://example.com) [Text](http://example.com "Title")
reStructuredText `Text <http://example.com/>`_
setext ^.. _Link_name URL
POD L<http://example.com/> L</Name>
Gemtext => gemini://example.com => gemini://example.com Text
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Gemtext and setext links must be on a line by themselves, they cannot be used inline.

More information Languages, Text syntax ...
Reference syntax
Languages Text syntaxTitle syntax
AsciiDoc
… [[id]] …
<<id>>
… [[id]] …
<<id,Text>>
… anchor:id …
xref:id
… anchor:id …
xref:id[Text]
Markdown
… [Text][id] …
[id]: http://example.com
… [Text][id] …
[id]: http://example.com "Title"
… [Text][] …
[Text]: http://example.com
… [Text][] …
[Text]: http://example.com "Title"
… [Text] …
[Text]: http://example.com
… [Text] …
[Text]: http://example.com "Title"
reStructuredText
… Name_ …
.. _Name: http://example.com
setext
… Link_name_ …
^.. _Link_name URL
Textile
… "Text":alias …
[alias]http://example.com
… "Text":alias …
[alias (Title)]http://example.com
Texy!
… "Text":alias …
[alias]: http://example.com
… "Text":alias …
[alias]: http://example.com .(Title)
Close

Org-mode's normal link syntax does a text search of the file. You can also put in dedicated targets with <<id>>.

List syntax

HTML requires an explicit element for the list, specifying its type, and one for each list item, but most lightweight markup languages need only different line prefixes for the bullet points or enumerated items. Some languages rely on indentation for nested lists, others use repeated parent list markers.

More information Characters:, * ...
Unordered, bullet list items
Characters: * - + # . · _ : indent skip nest
Markdown YesYesYesNoNoNoNoNoNoNoNo0–31–3indent
MediaWiki, TiddlyWiki YesNoNoNoNoNoNoNoNoNoNo01+repeat
Org-mode Yes[51]YesYesNoNoNoNoNoNoNoNo0+indent
Jira YesYesNoNoNoNoNoNoNoNoNo01+repeat
Gemtext YesNoNoNoNoNoNoNoNoNoNo01+No
Textile YesNoNoNoNoNoNoNoNoNoNo01+repeat
Close

Microsoft Word automatically converts paragraphs that start with an asterisk *, hyphen-minus - or greater-than bracket > followed by a space or horizontal tabulator as bullet list items. It will also start an enumerated list for the digit 1 and the case-insensitive letters a (for alphabetic lists) or i (for roman numerals), if they are followed by a period ., a closing round parenthesis ), a greater-than sign > or a hyphen-minus - and a space or tab; in case of the round parenthesis an optional opening one ( before the list marker is also supported.

Languages differ on whether they support optional or mandatory digits in numbered list items, which kinds of enumerators they understand (e.g. decimal digit 1, roman numerals i or I, alphabetic letters a or A) and whether they support to keep explicit values in the output format. Some Markdown dialects, for instance, will respect a start value other than 1, but ignore any other explicit value.

More information Chars:, + ...
Ordered, enumerated list items
Chars: + # #1 1. 1) 1] 1} (1) [1] {1} a. A. i. I. indent skip nest
Markdown NoNoNoYesYesNoNoNoNoNoNoNoNoNo0–31–3indent
MediaWiki, TiddlyWiki NoYesNoNoNoNoNoNoNoNoNoNoNoNo01+repeat
Org-mode NoNoNoYesYesNoNoNoNoNoOptionalNoNo0+indent
Jira, Textile NoYesNoNoNoNoNoNoNoNoNoNoNoNo01+repeat
Close

Slack assists the user in entering enumerated and bullet lists, but does not actually format them as such, i.e. it just includes a leading digit followed by a period and a space or a bullet character in front of a line.

More information Languages, Term being defined ...
Labeled, glossary, definition list syntax
Languages Term being definedDefinition of the term
MediaWiki ; Term : Definition
Textile
TiddlyWiki
Org-mode - Term :: Definition
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Historical formats

The following lightweight markup languages, while similar to some of those already mentioned, have not yet been added to the comparison tables in this article:

  • EtText:[52] circa 2000
  • Grutatext:[53] circa 2002

See also

References

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