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{{Short description|HyperText Markup Languagelanguage for documents}}

{{Redirect2|.htm|.html||HTM (disambiguation){{!}}HTM}}

{{pp-vandalism|small=yes}}

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{{HTML}}

'''Hypertext Markup Language''' ('''HTML''') is the standard [[markup language]]{{efn|Even though HTML can be run in a browser, it is not viewed as a [[programming language]] in programming language discourse.<ref>{{Cite book |author-link=Felienne Hermans|last1=Hermans |first1=Felienne |last2=Schlesinger |first2=Ari |chapter=A Case for Feminism in Programming Language Design |date=2024-10-17 |title=Proceedings of the 2024 ACM SIGPLAN International Symposium on New Ideas, New Paradigms, and Reflections on Programming and Software |chapter-url=https://dl.acm.org/doi/10.1145/3689492.3689809A Case for Feminism in Programming Language Design |journaldate=[[OOPSLA]]2024-10-17 |language=en |publisher=ACM |pages=205–222 |doi=10.1145/3689492.3689809 |isbn=979-8-4007-1215-9}}</ref>}} for documents designed to be displayed in a [[web browser]]. It defines the content and structure of [[web content]]. It is often assisted by technologies such as [[Cascading Style Sheets]] (CSS) and [[scripting language]]s such as [[JavaScript]], a programming language.

[[Web browser]]s receive HTML documents from a [[web server]] or from local storage and [[browser engine|render]] the documents into multimedia web pages. HTML describes the structure of a [[web page]] [[Semantic Web|semantically]] and originally included cues for its appearance.

[[HTML element]]s are the building blocks of HTML pages. With HTML constructs, [[HTML element#Images and objects|images]] and other objects such as [[Fieldset|interactive forms]] may be embedded into the rendered page. HTML provides a means to create [[structured document]]s by denoting structural [[semantics]] for text such as headings, paragraphs, lists, [[Hyperlink|links]], quotes, and other items. HTML elements are delineated by ''tags'', written using [[Bracket#Angle brackets|angle brackets]]. Tags such as {{code|lang=html|code=<img>}} and {{code|lang=html|<input>}} directly introduce content into the page. Other tags such as {{code|lang=html|code=<p>}} and {{code|lang=html|code=</p>}} surround and provide information about document text and may include sub-element tags. [[Web browser|Browsers]] do not display the HTML tags, but use them to interpret the content of the page.

HTML can embed programs written in a [[scripting language]] such as [[JavaScript]], which affects the behavior and content of web pages. The inclusion of CSS defines the look and layout of content. The [[World Wide Web Consortium]] (W3C), former maintainer of the HTML and current maintainer of the CSS standards, has encouraged the use of [[CSS]] over explicit presentational HTML {{as of|1997|lc=y|since=y|post=.}}<ref name="deprecated">{{cite web|title=HTML 4.0 Specification — W3C Recommendation — Conformance: requirements and recommendations |url=https://www.w3.org/TR/REC-html40-971218/conform.html#deprecated|date=December 18, 1997|publisher=World Wide Web Consortium|url-status=live|archive-url=https://web.archive.org/web/20150705040855/http://www.w3.org/TR/REC-html40-971218/conform.html|archive-date=July 5, 2015|access-date=July 6, 2015}}</ref> A form of HTML, known as [[HTML5]], is used to display video and audio, primarily using the {{code|lang=html|<canvas>}} element, together with JavaScript.

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The general form of an HTML element is therefore: {{code|lang=html|code=<tag attribute1="value1" attribute2="value2">''content''</tag>}}. Some HTML elements are defined as ''empty elements'' and take the form {{code|lang=html|code=<tag attribute1="value1" attribute2="value2">}}. Empty elements may enclose no content, for instance, the {{code|lang=html|code=<br>}} tag or the inline {{code|lang=html|code=<img>}} tag.

The name of an HTML element is the name used in the tags.

The end tag's name is preceded by a slash character, <code>&#47;</code>,. andIf thata intag emptyhas elementsno thecontent, an end tag is neithernot requiredallowed. norIf allowedattributes are not mentioned, default values are used in each case.

If attributes are not mentioned, default values are used in each case.

==== Element examples ====

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===== Line breaks =====

{{code|lang=html|code=<br>}}. The difference between {{code|lang=html|code=<br>}} and {{code|lang=html|code=<p>}} is that {{code|lang=html|code=<br>}} [[line breaking character|breaks a line]] without altering the semantic structure of the page, whereas {{code|lang=html|code=<p>}} sections the page into [[paragraph]]s. The element {{code|code=<br>|lang=html}} is an ''empty element'' in that, although it may have attributes, it can take no content and it maymust not have an end tag.

<syntaxhighlight lang="html"><p>This <br> is a paragraph <br> with <br> line breaks</p></syntaxhighlight>

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Escaping also allows for characters that are not easily typed, or that are not available in the document's [[character encoding]], to be represented within the element and attribute content. For example, the acute-accented <code>e</code> (<code>é</code>), a character typically found only on Western European and South American keyboards, can be written in any HTML document as the entity reference <code>&amp;eacute;</code> or as the numeric references <code>&amp;#xE9;</code> or <code>&amp;#233;</code>, using characters that are available on all keyboards and are supported in all character encodings. [[Unicode]] character encodings such as [[UTF-8]] are compatible with all modern browsers and allow direct access to almost all the characters of the world's writing systems.<ref>{{cite web|title=''The Unicode Standard'': A Technical Introduction |publisher=Unicode |url=https://www.unicode.org/standard/principles.html|access-date=2010-03-16}}</ref>

{| class="wikitable"

|+HTML escape sequence examples

|+Example HTML Escape Sequences

!Named

!Decimal

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=== Document type declaration ===

HTML documents are required to start with a d[[Document type declaration|ocumentdocument type declaration]] (informally, a "doctype"). In browsers, the doctype helps to define the rendering mode—particularly whether to use [[quirks mode]].

The original purpose of the doctype was to enable the parsing and validation of HTML documents by SGML tools based on the [[document type definition]] (DTD). The DTD to which the DOCTYPE refers contains a machine-readable grammar specifying the permitted and prohibited content for a document conforming to such a DTD. Browsers, on the other hand, do not implement HTML as an application of SGML and as consequence do not read the DTD.

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* Use the empty-element syntax only for elements specified as empty in HTML.

* Remove the closing slash in empty-element tags: for example {{code|lang=html|code=<br>}} instead of {{code|lang=html|code=<br/>}}.

* Include explicit close tags for elements that permit content but are left empty (for example, {{code|lang=html|code=<div></div>}}, not {{code|lang=html|code=<div />}}).

* Omit the XML declaration.

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== WHATWG HTML versus HTML5 ==

{{Main|#Transition of HTML Publicationpublication to WHATWG}}

The HTML Living Standard, which is developed by WHATWG, is the official version, while W3C HTML5 is no longer separate from WHATWG.

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There are some [[WYSIWYG]] editors (''what you see is what you get''), in which the user lays out everything as it is to appear in the HTML document using a [[graphical user interface]] (GUI), often similar to [[word processor]]s. The editor renders the document rather than showing the code, so authors do not require extensive knowledge of HTML.

The WYSIWYG editing model has been criticized,<ref>Sauer, C.: WYSIWIKI&nbsp;– Questioning WYSIWYG in the Internet Age. In: Wikimania (2006)</ref><ref>Spiesser, J., Kitchen, L.: Optimization of HTML automatically generated by WYSIWYG programs. In: 13th International Conference on World Wide Web, pp. 355—364355–364. WWW '04. ACM, New York, NY (New York, NY, U.S., May 17–20, 2004)</ref> primarily because of the low quality of the generated code; there are voices{{who|date=June 2020}} advocating a change to the [[WYSIWYM]] model (''what you see is what you mean'').

WYSIWYG editors remain a controversial topic because of their perceived flaws such as: