View source for HTML5

{{Short description|Fifth and previous version of hypertext markup language}}
{{Infobox file format
| name      = HTML5<br /><small>(Previous W3C Recommendation)</small>
| icon      = HTML5-logo.svg
| icon_size = 130px
| caption   = HTML5 official logo, introduced on 18 January 2011
| extension = <code>.html</code>, <code>.htm</code>
| mime      = text/html
| developer = {{unbulleted list|[[Organization:WHATWG|WHATWG]]|[[Organization:World Wide Web Consortium|World Wide Web Consortium]] (W3C; formerly)}}
| released  = {{start date and age|df=y|2008|01|22|p=yes|br=yes}}<ref name="HTML5v1" />
| latest release version = 5.2 (Second revision)
| latest release date = {{start date and age|df=y|2017|12|14|p=yes|br=yes}}<ref name="HTML52 History" />
| standard  = [https://www.w3.org/standards/history/html52/ HTML 5.2]
| extended_from = [[HTML|HTML4]], [[XHTML|XHTML1]], DOM2 HTML
| extended_to = HTML LS
| open      = Yes
| type_code = TEXT
| uniform_type = public.html<ref>{{cite web |url= https://developer.apple.com/library/mac/#documentation/Miscellaneous/Reference/UTIRef/Articles/System-DeclaredUniformTypeIdentifiers.html |title=Mac Developer Library: System-Declared Uniform Type Identifiers | publisher=[[Company:Apple Inc.|Apple]] |date=17 November 2009}}</ref>
| owner     = W3C
| genre     = [[Markup language]]
}}
{{HTML}}
'''HTML5''' ('''Hypertext Markup Language 5''') is a [[Markup language|markup language]] used for structuring and presenting [[Hypertext|hypertext]] documents on the [[World Wide Web]]. It was the fifth and final<ref name="W3C transfer ZDNet" /> major [[HTML]] version that is now a retired [[Organization:World Wide Web Consortium|World Wide Web Consortium]] (W3C) recommendation. The current specification is known as the HTML Living Standard. It is maintained by the Web Hypertext Application Technology Working Group (WHATWG), a consortium of the major browser vendors ([[Company:Apple Inc.|Apple]], [[Company:Google|Google]], Mozilla, and [[Company:Microsoft|Microsoft]]).

HTML5 was first released in a public-facing form on 22 January 2008,<ref name="HTML5v1" /> with a major update and "W3C Recommendation" status in October 2014.<ref name="finalars" /><ref>{{cite web |url= https://www.w3.org/blog/news/archives/4167 |title=HTML5 is a W3C recommendation |work=W3C Blog |publisher=[[Organization:World Wide Web Consortium|World Wide Web Consortium]] |date=28 October 2014 |access-date=28 October 2014}}</ref> Its goals were to improve the language with support for the latest [[Engineering:Multimedia|multimedia]] and other new features; to keep the language both easily readable by humans and consistently understood by computers and devices such as [[Software:Web browser|web browser]]s, [[Parsing|parsers]], etc., without [[XHTML|XHTML's]] rigidity; and to remain backward-compatible with older software. HTML5 is intended to subsume not only HTML&nbsp;4 but also XHTML1 and even the [[Document Object Model|DOM]] Level 2 HTML itself.<ref name="HTML5diffHTML4-quote">{{cite web |title=HTML5 Differences from HTML4 |url= https://www.w3.org/TR/2014/NOTE-html5-diff-20141209/ |work=W3.org |publisher=W3C |access-date=2 March 2018 |quote= HTML4 became a W3C Recommendation in 1997. While it continues to serve as a rough guide to many of the core features of HTML, it does not provide enough information to build implementations that interoperate with each other and, more importantly, with Web content. The same goes for XHTML1, which defines an XML serialization for HTML4, and DOM Level 2 HTML, which defines JavaScript APIs for both HTML and XHTML. HTML replaces these documents. |at=Introduction}}</ref>

HTML5 includes detailed processing models to encourage more interoperable implementations; it extends, improves, and rationalizes the markup available for documents and introduces markup and [[Application programming interface|application programming interface]]s (APIs) for complex [[Web application|web application]]s.<ref name="HTML5diffHTML4">{{cite web |title=HTML5 Differences from HTML4 |url= https://www.w3.org/TR/html5-diff/ |work=W3.org |publisher=W3C |date=19 October 2010 |access-date=4 December 2010}}</ref> For the same reasons, HTML5 is also a candidate for cross-platform mobile applications because it includes features designed with low-powered devices in mind.

Many new [[Syntax (programming languages)|syntactic]] features are included. To natively include and handle multimedia and [[2D computer graphics|graphical]] content, the new [[HTML5 video|{{tag|video|o}}]], {{tag|audio|o}} and [[Canvas element|{{tag|canvas|o}}]] [[HTML element|elements]] were added; expandable sections are natively implemented through {{tag|summary}} and {{tag|details}} rather than depending on CSS or JavaScript; and support for scalable vector graphics (SVG) content and [[MathML]] for mathematical formulas was also added. To enrich the [[Semantic Web|semantic]] content of documents, new page structure elements such as {{tag|main|o}}, {{tag|section|o}}, [[Article element (HTML5)|{{tag|article|o}}]], {{tag|header|o}}, {{tag|footer|o}}, {{tag|aside|o}}, {{tag|nav|o}}, and {{tag|figure|o}} are added. New [[HTML attribute|attributes]] were introduced, some elements and attributes were removed, and others such as {{tag|a|o}}, {{tag|cite|o}}, and {{tag|menu|o}} were changed, redefined, or standardized. The APIs and [[Document Object Model]] (DOM) are now fundamental parts of the HTML5 specification,<ref name="HTML5diffHTML4" /> and HTML5 also better defines the processing for any invalid documents.<ref>{{cite web |title=HTML 5.2 W3C Recommendation |at=§ 1.10.2 Syntax Errors |url= https://www.w3.org/TR/html5/introduction.html#syntax-errors |work=W3.org |publisher=W3C |date=14 December 2017 |access-date=29 June 2017}}</ref>

==History==
The Web Hypertext Application Technology Working Group (WHATWG) began work on the new standard in 2004. At that time, HTML&nbsp;4.01 had not been updated since 2000,<ref>{{cite web|title=HTML&nbsp;4 Errata|url=https://www.w3.org/MarkUp/html4-updates/errata|publisher= [[Organization:World Wide Web Consortium|World Wide Web Consortium]] |access-date=4 December 2010}}</ref> and the [[Organization:World Wide Web Consortium|World Wide Web Consortium]] (W3C) was focusing future developments on XHTML&nbsp;2.0. In 2009, the W3C allowed the [[XHTML]] 2.0 Working Group's charter to expire and decided not to renew it.<ref name="W3C hist" />

The [[Organization:Mozilla Foundation|Mozilla Foundation]] and Opera Software presented a position paper at a World Wide Web Consortium workshop in June 2004,<ref>{{cite web |url= https://www.w3.org/2004/04/webapps-cdf-ws/papers/opera.html |title=Position Paper for the W3C Workshop on Web Applications and Compound Documents |work=W3.org |publisher=W3C |access-date=30 December 2011}}</ref> focusing on developing technologies that are backward-compatible with existing browsers,<ref>{{cite web |url= https://www.w3.org/2004/04/webapps-cdf-ws/minutes-20040601.html#topic18.1 |title=W3C Workshop on Web Applications and Compound Documents (Day 1) |date=1 June 2004 |work=W3.org |publisher=W3C |access-date=30 December 2011}}</ref> including an initial draft specification of Web Forms 2.0. The workshop concluded with a vote—8 for, 14 against—for continuing work on HTML.<ref>{{cite web |url= https://www.w3.org/2004/04/webapps-cdf-ws/minutes-20040602.html#topic28.1 |title=W3C Workshop on Web Applications and Compound Documents (Day 2) |date=2 June 2004 |work=W3.org |publisher=W3C |access-date=30 December 2011}}</ref> Immediately after the workshop, WHATWG was formed to start work based upon that position paper, and a second draft, Web Applications 1.0, was also announced.<ref>{{cite web |url= http://lists.w3.org/Archives/Public/public-whatwg-archive/2004Jun/0000.html |title=&#91;whatwg&#93; WHAT open mailing list announcement |first=-Ian |last=Hickson |work=Lists.W3.org |publisher=W3C |date=5 June 2004 |access-date=8 December 2015}}</ref> The two specifications were later merged to form HTML5.<ref>{{cite web |url= https://blog.whatwg.org/this-week-in-html-5-episode-5 |title=This Week in HTML 5 – Episode 5 |first=Mark |last=Pilgrim |author-link=Mark Pilgrim |work=WHATWG Blog |publisher=[[Organization:WHATWG|WHATWG]] |date=15 September 2008 |access-date=30 December 2011}}</ref> The HTML5 specification was adopted as the starting point of the work of the new HTML working group of the W3C in 2007.

WHATWG's Ian Hickson ([[Company:Google|Google]]) and David Hyatt ([[Company:Apple Inc.|Apple]]) produced W3C's first public working draft of the specification on 22 January 2008.<ref name="HTML5v1">{{cite web |url= https://www.w3.org/TR/2008/WD-html5-20080122/ |title=HTML5: A vocabulary and associated APIs for HTML and XHTML |date=22 January 2008 |work=W3.org |publisher=W3C |access-date=28 January 2009 }}</ref>

=== "Thoughts on Flash" ===
While some features of HTML5 are often compared to [[Software:Adobe Flash|Adobe Flash]], the two technologies are very different. Both include features for playing audio and video within web pages, and for using [[Scalable Vector Graphics]]. However, HTML5 on its own cannot be used for animation or interactivity&nbsp;– it must be supplemented with CSS3 or [[JavaScript]]. There are many Flash capabilities that have no direct counterpart in HTML5 (see [[Comparison of HTML5 and Flash]]). HTML5's interactive capabilities became a topic of mainstream media attention around April 2010<ref>{{cite news|url=http://www.foxnews.com/scitech/2010/04/29/flash-iphone-apples-steve-jobs-finally-explains/|title=FOX News: No Flash on the iPhone? Apple's Steve Jobs Finally Explains Why | publisher=Fox News Channel | date=29 April 2010}}</ref><ref>{{cite magazine|url=http://techland.time.com/2010/04/29/steve-jobs-flash-is-no-longer-necessary-and-other-musings/|title=TIME: Steve Jobs: 'Flash is No Longer Necessary' and Other Musings | magazine=Time | date=29 April 2010}}</ref><ref>{{cite news|url=http://www.cbsnews.com/8301-501465_162-20003744-501465.html|title=Steve Jobs: Why Apple Banned Flash|publisher=CBS News}}</ref><ref>{{cite web|url=http://www.fastcompany.com/1633336/steve-jobs-flash-adobe-apple-iphone-os-mac-software-open-standards-proprietary-open-letter|title=FastCompany: Steve Jobs: Adobe's Flash Is Old PC History, Open Web Is the Future|date=29 April 2010}}</ref> after [[Company:Apple Inc.|Apple Inc.]]'s then-CEO [[Biography:Steve Jobs|Steve Jobs]] issued a public letter titled "Thoughts on Flash" in which he concluded that "Flash is no longer necessary to watch video or consume any kind of web content" and that "new open standards created in the mobile era, such as HTML5, will win".<ref>{{cite web |last=Jobs |first=Steve |title=Thoughts on Flash |url=https://www.apple.com/hotnews/thoughts-on-flash/ |archive-url=https://web.archive.org/web/20100519224402/https://www.apple.com/hotnews/thoughts-on-flash/ |archive-date=2010-05-19 |access-date= |website=Apple.com}}</ref> This sparked a debate in web development circles suggesting that, while HTML5 provides enhanced functionality, developers must consider the varying browser support of the different parts of the standard as well as other functionality differences between HTML5 and Flash.<ref>{{cite web|url=http://www.lyquix.com/blog/122-is-html5-replacing-flash |title=Is HTML5 Replacing Flash? |publisher=Lyquix.com |access-date=8 January 2014}}</ref> In early November 2011, [[Company:Adobe Inc.|Adobe]] announced that it would discontinue the development of Flash for mobile devices and reorient its efforts in developing tools using HTML5.<ref>{{cite web|url=http://blogs.adobe.com/digitalmedia/2011/11/flash-to-focus-on-pc-browsing-and-mobile-apps-adobe-to-more-aggressively-contribute-to-html5/|title=Flash to Focus on PC Browsing and Mobile Apps; Adobe to More Aggressively Contribute to HTML5 |website=adobe.com |access-date=26 February 2012}}</ref> On 25 July 2017, Adobe announced that both the distribution and support of Flash would cease by the end of 2020.<ref>{{cite web|last1=Warren|first1=Tom|title=Adobe will finally kill Flash in 2020|url=https://www.theverge.com/2017/7/25/16026236/adobe-flash-end-of-support-2020|website=[[The Verge]]|date=25 July 2017}}</ref> Adobe itself officially discontinued Flash on 31 December 2020 and all Flash content was blocked from running in Flash Player as of 12 January 2021.<ref>{{cite news |last1=Lotus |first1=Jean |title=Adobe Flash reaches end of life with nostalgia from users |url=https://www.upi.com/Top_News/US/2021/01/01/Adobe-Flash-reaches-end-of-life-with-nostalgia-from-users/4501609550498/ |date=1 January 2021 |agency=UPI |language=en}}</ref>

=== Last call, candidacy, and recommendation stages ===

On 14 February 2011, the W3C extended the charter of its HTML Working Group with clear milestones for HTML5. In May 2011, the working group advanced HTML5 to "Last Call", an invitation to communities inside and outside W3C to confirm the technical soundness of the specification. The W3C developed a comprehensive test suite to achieve broad interoperability for the full specification by 2014, which was the target date for recommendation.<ref name="w3c2014">{{cite web
|url=https://www.w3.org/2011/02/htmlwg-pr.html
|title=W3C Confirms May 2011 for HTML5 Last Call, Targets 2014 for HTML5 Standard
|publisher= [[Organization:World Wide Web Consortium|World Wide Web Consortium]]
|access-date=18 February 2011

In July 2012, WHATWG and W3C decided on a degree of separation. W3C will continue the HTML5 specification work, focusing on a single definitive standard, which is considered a "snapshot" by WHATWG. The WHATWG organization continues its work with HTML5 as a "living standard". The concept of a living standard is that it is never complete and is always being updated and improved. New features can be added but functionality will not be removed.<ref name="splits">{{cite web |url= http://www.netmagazine.com/news/html5-gets-splits-122102 |title=HTML5 gets the splits |work=NetMagazine.com |access-date=23 July 2012 }}</ref>

In December 2012, W3C designated HTML5 as a Candidate Recommendation.<ref>{{cite web|url=https://www.w3.org/TR/2012/CR-html5-20121217/ |title=HTML5 |publisher=W3.org |date=17 December 2012 |access-date=15 June 2013}}</ref> The criterion for advancement to [[Organization:World Wide Web Consortium#W3C recommendation (REC)|W3C Recommendation]] is "two 100% complete and fully interoperable implementations".<ref name="W3Crec">{{cite web
|url=http://wiki.whatwg.org/wiki/FAQ#What.27s_this_I_hear_about_2022.3F
|title= When Will HTML5 Be Finished?
|work=FAQ
|publisher=WHAT Working Group
|access-date=29 November 2009}}</ref>

On 16 September 2014, W3C moved HTML5 to Proposed Recommendation.<ref>{{cite web|url=https://www.w3.org/blog/news/archives/4074 |title=Call for Review: HTML5 Proposed Recommendation Published W3C News |work=W3.org |publisher=W3C |date=16 September 2014 |access-date=27 September 2014}}</ref> On 28 October 2014, HTML5 was released as a W3C Recommendation,<ref>{{cite web | url=https://www.w3.org/2014/10/html5-rec.html.en | title=Open Web Platform Milestone Achieved with HTML5 Recommendation |work=W3.org |publisher=W3C | date=28 October 2014 |access-date=29 October 2014}}</ref> bringing the specification process to completion.<ref name=finalars /> On 1 November 2016, HTML 5.1 was released as a W3C Recommendation.<ref>{{cite web|title=HTML 5.1 W3C Recommendation |url= https://www.w3.org/TR/2016/REC-html51-20161101/ |work=W3.org |publisher=W3C |access-date=26 February 2017}}</ref> On 14 December 2017, HTML 5.2 was released as a W3C Recommendation.<ref>{{cite web|title=HTML 5.2 W3C Recommendation |url= https://www.w3.org/TR/2017/REC-html52-20171214/ |work=W3.org |publisher=W3C |access-date=14 December 2017}}</ref>

=== Retirement ===
The W3C retired HTML5 on 27 March 2018.<ref>{{cite web |title=HTML5 Publication History - W3C |url=https://www.w3.org/standards/history/html5}}</ref> Additionally, the retirement included HTML 4.0,<ref>{{cite web |title=HTML 4.0 Publication History - W3C |url=https://www.w3.org/standards/history/html40}}</ref> HTML 4.01,<ref>{{cite web |title=HTML 4.01 Publication History - W3C |url=https://www.w3.org/standards/history/html401}}</ref> XHTML 1.0,<ref>{{cite web |title=XHTML™ 1.0 The Extensible HyperText Markup Language (Second Edition) Publication History - W3C |url=https://www.w3.org/standards/history/xhtml1}}</ref> and XHTML 1.1.<ref>{{cite web |title=XHTML™ 1.1 - Module-based XHTML - Second Edition Publication History - W3C |url=https://www.w3.org/standards/history/xhtml11}}</ref> HTML 5.1, HTML 5.2 and HTML 5.3 were all retired on 28 January 2021, in favour of the HTML living standard.<ref>{{cite web |title=HTML 5.2 Publication History - W3C |url=https://www.w3.org/standards/history/html52}}</ref><ref>{{cite web |title=HTML 5.3 Publication History - W3C |url=https://www.w3.org/standards/history/html53}}</ref>

=== Timeline ===

The combined timelines for the W3C recommendations of HTML5, HTML 5.1, HTML 5.2 and HTML 5.3:

{| class="wikitable"
|-
! Version !! First draft !! Candidate<br> recommendation !! Recommendation !! Retired
|-
| HTML5 || 1 May 2007<ref>{{Cite web|url=http://www.whatwg.org:80/specs/web-apps/current-work/multipage/|archive-url=https://web.archive.org/web/20070503155417/http://www.whatwg.org:80/specs/web-apps/current-work/multipage/|url-status=dead|archive-date=3 May 2007|title=Web Applications 1.0|date=3 May 2007|access-date=18 September 2018}}</ref>|| 17 December 2012 || 28 October 2014 || 27 March 2018<ref>{{cite web |url=https://www.w3.org/standards/history/html5|title=HTML5 Publication History - W3C}}</ref>
|-
| HTML 5.1 || 17 December 2012 || 21 June 2016 || 1 November 2016 || rowspan=2 | 28 January 2021<ref>{{cite web |url=https://www.w3.org/standards/history/html51|title=HTML 5.1 2nd Edition Publication History - W3C}}</ref>
|-
| HTML 5.1<br> 2nd Edition || {{N/A}} || 20 June 2017 || 3 October 2017
|-
| HTML 5.2 || 18 August 2016 || 8 August 2017 || 14 December 2017 || 28 January 2021<ref name="HTML52 History">{{cite web |url=https://www.w3.org/standards/history/html52|title=HTML 5.2 Publication History - W3C}}</ref>
|-
| HTML 5.3 || 14 December 2017<ref name="5.3FWD">{{cite web|url=https://www.w3.org/TR/2017/WD-html53-20171214/|title=HTML 5.3|date=14 December 2017|id=W3C First Public Working Draft|publisher=[[Organization:World Wide Web Consortium|World Wide Web Consortium]]}}</ref> || {{N/A}} || {{N/A}} || 28 January 2021<ref>{{cite web |url=https://www.w3.org/standards/history/html53|title=HTML 5.3 Publication History - W3C}}</ref>
|}

=== W3C and WHATWG conflict ===
The W3C ceded authority over the HTML and DOM standards to WHATWG on 28 May 2019, as it considered that having two standards is harmful.<ref name="W3C transfer blog">{{cite web|url=https://www.w3.org/blog/2019/05/w3c-and-whatwg-to-work-together-to-advance-the-open-web-platform/|title=W3C and WHATWG to Work Together to Advance the Open Web Platform|last1=Jaffe|first1=Jeff|date=28 May 2019|website=W3C Blog|archive-url=https://web.archive.org/web/20190529021122/https://www.w3.org/blog/2019/05/w3c-and-whatwg-to-work-together-to-advance-the-open-web-platform/|archive-date=29 May 2019|url-status=live|access-date=29 May 2019}}</ref><ref name="W3C transfer HTML">{{cite web|url=https://www.w3.org/html/|title=W3C and the WHATWG Signed an Agreement to Collaborate on a Single Version of HTML and DOM|date=28 May 2019|website=W3C|archive-url=https://web.archive.org/web/20190529012655/https://www.w3.org/html/|archive-date=29 May 2019|url-status=live|access-date=29 May 2019}}</ref><ref name="W3C transfer memo">{{cite web|url=https://www.w3.org/2019/04/WHATWG-W3C-MOU.html|title=Memorandum of Understanding Between W3C and WHATWG|date=28 May 2019|website=W3C|archive-url=https://web.archive.org/web/20190529012854/https://www.w3.org/2019/04/WHATWG-W3C-MOU.html|archive-date=29 May 2019|url-status=live|access-date=29 May 2019}}</ref><ref name="W3C transfer ZDNet">{{cite news |last1=Cimpanu |first1=Catalin |title=Browser vendors Win War with W3C over HTML and DOM standards |url=https://www.zdnet.com/article/browser-vendors-win-war-with-w3c-over-html-and-dom-standards/ |access-date=29 May 2019 |publisher=ZDNet |date=29 May 2019 |archive-url=https://web.archive.org/web/20190529021959/https://www.zdnet.com/article/browser-vendors-win-war-with-w3c-over-html-and-dom-standards/ |archive-date=29 May 2019}}</ref> The HTML Living Standard is now authoritative. However, W3C will still participate in the development process of HTML.

Before the ceding of authority, W3C and WHATWG had been characterized as both working together on the development of HTML5,<ref name="W3C hist">{{cite web |title=HTML 5.2 W3C Recommendation |at=§ 1.4 History |url= https://www.w3.org/TR/html/introduction.html#introduction-history |work=W3.org |publisher=W3C |date=14 December 2017 |access-date=9 August 2017}}</ref> and yet also at cross purposes<ref name="splits" /><ref name="finalars" /> ever since the July 2012 split. The W3C "HTML5" standard was snapshot-based (HTML5, HTML 5.1, etc.) and static, while the WHATWG "HTML living standard" is continually updated. The relationship had been described as "fragile", even a "rift",<ref name="tale">{{cite web |title=A Tale of Two Standards |first=Jay |last=Hoffmann |work=The History of the Web |year=2017 |url= https://thehistoryoftheweb.com/when-standards-divide/ |url-status=live |archive-url= https://web.archive.org/web/20170901211055/https://thehistoryoftheweb.com/when-standards-divide/ |archive-date=1 September 2017 |access-date=26 January 2018}} (Original title: "When Standards Divide".)</ref> and characterized by "squabbling".<ref name="finalars">{{cite web |url= https://arstechnica.com/information-technology/2014/10/html5-specification-finalized-squabbling-over-who-writes-the-specs-continues/ |title=HTML5 specification finalized, squabbling over specs continues |publisher=Ars Technica |date=29 October 2014 |access-date=29 October 2014}}</ref>

In at least one case, namely the permissible content of the {{tag|cite|o}} element, the two specifications directly contradicted each other ({{as of|lc=y|2018|07|post=),}} with the W3C definition allowing a broader range of uses than the WHATWG definition.<ref>{{cite web |at=§ 4.5.6. The cite element |title=HTML 5.2 W3C Recommendation |date=14 December 2017 |work=W3.org |publisher=W3C |url= https://www.w3.org/TR/html52/textlevel-semantics.html#the-cite-element |access-date=26 July 2018}}</ref><ref>{{cite web |at=§ 4.5.6 The cite element |title=HTML Living Standard |date=25 July 2018 |work=HTML.spec.WHATWG.org |publisher=[[Organization:WHATWG|WHATWG]] |url= https://html.spec.whatwg.org/multipage/text-level-semantics.html#the-cite-element |access-date=26 July 2018}}</ref>

The "Introduction" section in the WHATWG spec (edited by Ian "Hixie" Hickson) is critical of W3C, e.g. "{{em|Note:}} Although we have asked them to stop doing so, the W3C also republishes some parts of this specification as separate documents." In its "History" subsection it portrays W3C as resistant to Hickson's and WHATWG's original HTML5 plans, then jumping on the bandwagon belatedly (though Hickson was in control of the W3C HTML5 spec, too). Regardless, it indicates a major philosophical divide between the organizations:<ref>{{cite web |at=§ 1 Introduction; §1.6 History |title=HTML Living Standard |date=25 July 2018 |work=HTML.spec.WHATWG.org |publisher=[[Organization:WHATWG|WHATWG]] |url= https://html.spec.whatwg.org/multipage/introduction.html |access-date=26 July 2018}}</ref>
{{Blockquote|<p>For a number of years, both groups then worked together. In 2011, however, the groups came to the conclusion that they had different goals: the W3C wanted to publish a "finished" version of "HTML5", while the WHATWG wanted to continue working on a Living Standard for HTML, continuously maintaining the specification rather than freezing it in a state with known problems, and adding new features as needed to evolve the platform.</p><p>Since then, the WHATWG has been working on this specification (amongst others), and the W3C has been copying fixes made by the WHATWG into their fork of the document (which also has other changes).</p>
}}

The two entities signed an agreement to work together on a single version of HTML on 28 May 2019.<ref>{{Cite web |url=https://www.w3.org/blog/news/archives/7753 |title=W3C and the WHATWG Signed an Agreement to Collaborate on a Single Version of HTML and DOM |publisher=W3C |date=28 May 2019 |access-date=29 May 2019}}</ref>

==== Differences between the two standards ====

In addition to the contradiction in the {{tag|cite|o}} element mentioned above, other differences between the two standards include at least the following, {{as of|September 2018|lc=y}}:
{| class="wikitable"
|+
Content or Features Unique to W3C or WHATWG Standard
!
!W3C<ref>{{Cite web|url=http://www.w3.org/TR/html/|title=HTML 5.2|website=w3.org|access-date=18 September 2018}}</ref>
!WHATWG<ref>{{Cite web|url=https://html.spec.whatwg.org/|title=HTML Standard|website=html.spec.whatwg.org|access-date=18 September 2018}}</ref>
|-
|Site pagination
|
|Single page version<ref>{{Cite web|url=https://html.spec.whatwg.org/|title=HTML Standard, One-Page Version|website=html.spec.whatwg.org|access-date=18 September 2018}}</ref> (allows global search of contents)
|-
|Chapters
|
|§5 ''Microdata''<ref name=":0">{{Cite web|url=https://html.spec.whatwg.org/#microdata|title=HTML Standard, Chapter 5: Microdata|website=html.spec.whatwg.org|access-date=19 September 2018}}</ref>
§9 ''Communication''<ref>{{Cite web|url=https://html.spec.whatwg.org/#comms|title=HTML Standard, Chapter 9: Communication|website=html.spec.whatwg.org|access-date=19 September 2018}}</ref>

§10 ''Web workers''<ref>{{Cite web|url=https://html.spec.whatwg.org/#workers|title=HTML Standard, Chapter 10: Web workers|website=html.spec.whatwg.org|access-date=19 September 2018}}</ref>

§11 ''Web storage''<ref>{{Cite web|url=https://html.spec.whatwg.org/#webstorage|title=HTML Standard, Chapter 11: Web storage|website=html.spec.whatwg.org|access-date=19 September 2018}}</ref>
|-
|Global attributes
|:<ref name=":2">{{Cite web|url=https://www.w3.org/TR/html/dom.html#global-attributes|title=HTML 5.2, § 3.2.5. Global attributes|website=w3.org|access-date=18 September 2018}}</ref> <code>class</code>, <code>id</code>
|:<ref name=":3">{{Cite web|url=https://html.spec.whatwg.org/#global-attributes|title=HTML Standard, § 3.2.6 Global attributes|website=html.spec.whatwg.org|access-date=18 September 2018}}</ref> <code>autocapitalize</code>, <code>enterkeyhint</code>, <code>inputmode</code>, <code>is</code>, <code>itemid</code>, <code>itemprop</code>, <code>itemref</code>, <code>itemscope</code>, <code>itemtype</code>, <code>nonce</code>
|-
|Chapter ''Elements of HTML''
|
|§4.13 ''Custom elements''<ref>{{Cite web|url=https://html.spec.whatwg.org/#custom-elements|title=HTML Standard, § 4.13 Custom elements|website=html.spec.whatwg.org|access-date=18 September 2018}}</ref>
|-
|Elements
|<code><nowiki><rb></nowiki></code>,<ref>{{Cite web|url=https://www.w3.org/TR/html/textlevel-semantics.html#the-rb-element|title=HTML 5.2: § 4.5.11. The rb element|website=w3.org|access-date=19 September 2018}}</ref> <code><nowiki><rtc></nowiki></code><ref>{{Cite web|url=https://www.w3.org/TR/html/textlevel-semantics.html#the-rtc-element|title=HTML 5.2: § 4.5.13. The rtc element|website=w3.org|access-date=19 September 2018}}</ref> (See compatibility notes below.)
<code><address></code><ref name=":1">{{Cite web|url=https://www.w3.org/TR/html/grouping-content.html#the-address-element|title=HTML 5.2: § 4.4.2. The address element|website=w3.org|access-date=19 September 2018}}</ref> is in section ''Grouping content''.
|<code><hgroup></code>,<ref>{{Cite web|url=https://html.spec.whatwg.org/#the-hgroup-element|title=HTML Standard, § 4.3.7 The hgroup element|website=html.spec.whatwg.org|access-date=19 September 2018}}</ref> <code><menu></code>,<ref>{{Cite web|url=https://html.spec.whatwg.org/#the-menu-element|title=HTML Standard, § 4.4.7 The menu element|website=html.spec.whatwg.org|access-date=19 September 2018}}</ref> <code><slot></code><ref>{{Cite web|url=https://html.spec.whatwg.org/#the-slot-element|title=HTML Standard, § 4.12.4 The slot element|website=html.spec.whatwg.org|access-date=19 September 2018}}</ref> (See compatibility notes below.)
<code><address></code><ref>{{Cite web|url=https://html.spec.whatwg.org/#the-address-element|title=HTML Standard, § 4.3.10 The address element|website=html.spec.whatwg.org|access-date=19 September 2018}}</ref> is in section ''Sections''.
|-
|§ <code><meta></code>
|§4.2.5.4. ''Other pragma directives'',<ref>{{Cite web|url=https://www.w3.org/TR/html/document-metadata.html#other-pragma-directives|title=HTML 5.2: § 4.2.5.4. Other pragma directives|website=w3.org|access-date=19 September 2018}}</ref> based on deprecated WHATWG procedure.<ref>{{Cite web|url=https://wiki.whatwg.org/wiki/PragmaExtensions|title=PragmaExtensions – WHATWG Wiki|website=wiki.whatwg.org|access-date=19 September 2018|quote=This document is obsolete.}}</ref>
|
|-
|§ Sections
|
|§ 4.3.11.2 ''Sample outlines''<ref>{{Cite web|url=https://html.spec.whatwg.org/#sample-outlines|title=HTML Standard, § 4.3.11.2 Sample outlines|website=html.spec.whatwg.org|access-date=19 September 2018}}</ref>
§ 4.3.11.3 ''Exposing outlines to users''<ref>{{Cite web|url=https://html.spec.whatwg.org/#exposing-outlines-to-users|title=HTML Standard, § 4.3.11.3 Exposing outlines to users|website=html.spec.whatwg.org|access-date=19 September 2018}}</ref>
|-
|Structured data
|Recommends RDFa (code examples,<ref>{{Cite web|url=https://www.w3.org/TR/html/sections.html#the-article-element|title=HTML 5.2: § 4.3.2. The article element|website=w3.org|access-date=18 September 2018}}</ref><ref name=":1" /><ref>{{Cite web|url=https://www.w3.org/TR/html/textlevel-semantics.html#the-time-element|title=HTML 5.2: § 4.5.16. The time element|website=w3.org|access-date=18 September 2018}}</ref> separate specs,<ref>{{Cite web|url=https://www.w3.org/TR/html-rdfa/|title=HTML+RDFa 1.1 – Second Edition|website=w3.org|access-date=18 September 2018}}</ref><ref>{{Cite web|url=https://www.w3.org/TR/rdfa-lite/|title=RDFa Lite 1.1 – Second Edition|website=w3.org|access-date=18 September 2018}}</ref> no special attributes<ref name=":2" />).
|Recommends Microdata (code examples,<ref>{{Cite web|url=https://html.spec.whatwg.org/#the-article-element|title=HTML Standard, § 4.3.2 The article element|website=html.spec.whatwg.org|access-date=18 September 2018}}</ref><ref>{{Cite web|url=https://html.spec.whatwg.org/#the-nav-element|title=HTML Standard, § 4.3.4 The nav element|website=html.spec.whatwg.org|access-date=18 September 2018}}</ref><ref>{{Cite web|url=https://html.spec.whatwg.org/#the-dl-element|title=HTML Standard, § 4.4.9 The dl element|website=html.spec.whatwg.org|access-date=18 September 2018}}</ref><ref>{{Cite web|url=https://html.spec.whatwg.org/#the-time-element|title=HTML Standard, § 4.5.14 The time element|website=html.spec.whatwg.org|access-date=18 September 2018}}</ref> spec chapter,<ref name=":0" /> special attributes<ref name=":3" />).
|}
The following table provides data from the Mozilla Development Network on compatibility with major browsers, {{as of|September 2018|lc=y}}, of HTML elements unique to one of the standards:
{| class="wikitable"
!Element
!Standard
!Compatibility
!Note
|-
|<code><nowiki><rb></nowiki><ref>{{Cite web|url=https://developer.mozilla.org/en-US/docs/Web/HTML/Element/rb|title=&lt;rb>: The Ruby Base element|website=MDN Web Docs|access-date=19 September 2018}}</ref></code>
|W3C
|All browsers, except Edge
|
|-
|<code><nowiki><rtc></nowiki><ref>{{Cite web|url=https://developer.mozilla.org/en-US/docs/Web/HTML/Element/rtc|title=&lt;rtc>: The Ruby Text Container element|website=MDN Web Docs|access-date=19 September 2018}}</ref></code>
|W3C
|None, except Firefox
|
|-
|<code><hgroup></code><ref>{{Cite web|url=https://developer.mozilla.org/en-US/docs/Web/HTML/Element/hgroup|title=<hgroup>|website=MDN Web Docs|access-date=19 September 2018}}</ref>
|WHATWG
|All browsers
|"[Since] the HTML outline algorithm is not implemented in any browsers ... the <code><hgroup></code> semantics are in practice only theoretical."
|-
|<code><menu></code><ref>{{Cite web|url=https://developer.mozilla.org/en-US/docs/Web/HTML/Element/menu|title=<menu>|website=MDN Web Docs|access-date=19 September 2018}}</ref>
|WHATWG
|Full support only in Edge and Firefox desktops.
Partial support in Firefox mobile.

Supported in Opera with user opt-in.

Not supported in other browsers. 
|Experimental technology
|-
|<code><slot><ref>{{Cite web|url=https://developer.mozilla.org/en-US/docs/Web/HTML/Element/slot|title=<slot>|website=MDN Web Docs|access-date=19 September 2018}}</ref></code>
|WHATWG
|All browsers, except IE
|Experimental technology
|}

== Features and APIs ==
The W3C proposed a greater reliance on modularity as a key part of the plan to make faster progress, meaning identifying specific features, either proposed or already existing in the spec, and advancing them as separate specifications. Some technologies that were originally defined in HTML5 itself are now defined in separate specifications:
* HTML Working Group&nbsp;— HTML Canvas 2D Context;
* Immersive Web Working Group&nbsp;— [[WebXR|WebXR Device API]], WebXR Gamepads Module, WebXR Augmented Reality Module, and others;<ref>{{cite web |url=https://immersive-web.github.io/ |title=The Immersive Web Working Group/Community Group |publisher=W3C |accessdate=2023-05-25 }}</ref>
* Web Apps Working Group&nbsp;— [[Web Messaging]], [[Web worker]]s, [[Web storage]], [[WebSocket]], [[Server-sent events]], [[Web Components]]<ref>{{cite web |url= https://www.w3.org/2008/webapps/wiki/PubStatus |title=PubStatus – WEBAPPS |work=W3.org |publisher=W3C}}</ref> (this was not part of HTML5, though); the Web Applications Working Group was closed in October 2015 and its deliverables transferred to the Web Platform Working Group (WPWG).
* IETF HyBi Working Group&nbsp;— WebSocket Protocol;
* WebRTC Working Group&nbsp;— [[Software:WebRTC|WebRTC]];
* Web Media Text Tracks Community Group&nbsp;— [[WebVTT]].

Some features that were removed from the original HTML5 specification have been standardized separately as modules, such as [[Microdata (HTML)|Microdata]] and [[Canvas element|Canvas]]. Technical specifications introduced as HTML5 extensions such as [[Polyglot markup]] have also been standardized as modules. Some W3C specifications that were originally separate specifications have been adapted as HTML5 extensions or features, such as [[Scalable Vector Graphics|SVG]]. Some features that might have slowed down the standardization of HTML5 were or will be standardized as upcoming specifications, instead.

==Features==

===Markup===
HTML5 introduces [[HTML element|elements]] and [[HTML attribute|attributes]] that reflect typical usage on modern websites. Some of them are semantic replacements for common uses of generic block ({{tag|div|open}}) and inline ({{tag|span|open}}) elements, for example {{tag|nav|open}} (website navigation block), {{tag|footer|open}} (usually referring to bottom of web page or to last lines of HTML code), or {{tag|audio|open}} and {{tag|video|open}} instead of {{tag|object|open}}.<ref>Introduction to HTML 5 [http://dev.opera.com/articles/view/introduction-html5-video/ video] {{Webarchive|url=https://web.archive.org/web/20110124043555/http://dev.opera.com/articles/view/introduction-html5-video/ |date=24 January 2011 }}</ref><ref>IBM Developer Works [http://www.ibm.com/developerworks/library/x-html5/?ca=dgr-lnxw01NewHTML New elements in HTML5: Structure and semantics] {{Webarchive|url=https://web.archive.org/web/20110105154130/http://www.ibm.com/developerworks/library/x-html5/?ca=dgr-lnxw01NewHTML |date=5 January 2011 }}</ref><ref>ICAMD.org [https://www.amazon.com/dp/B003H05Q18 Finalcut Silverlight Films that Videographers share Quicktime in a Flash: Video on the Web using HTML5 and other Codecs] {{Webarchive|url=https://web.archive.org/web/20221126002554/https://www.amazon.com/dp/B003H05Q18 |date=26 November 2022 }}</ref>
Some deprecated elements from HTML&nbsp;4.01 have been dropped, including purely presentational elements such as {{tag|font|open}} and {{tag|center|open}}, whose effects have long been superseded by the more capable [[Cascading Style Sheets]].<ref>
 {{cite web
 | url = https://www.w3.org/TR/html5/obsolete.html
 | title = 11 Obsolete features – HTML5
 | publisher = W3C
 | access-date = 11 March 2014}}</ref> There is also a renewed emphasis on the importance of client-side [[JavaScript]] used to create [[Dynamic web page|dynamic web page]]s.{{Citation needed|date=March 2021}}

The HTML5 syntax is no longer based on [[Standard Generalized Markup Language|SGML]]<ref>[https://jkorpela.fi/html5-dtd.html HTML5 DTD] {{Webarchive|url=https://web.archive.org/web/20221126002601/https://jkorpela.fi/html5-dtd.html |date=26 November 2022 }}: "HTML5 is not SGML-based, and there will be no official DTD for it."</ref><ref>[https://dev.w3.org/html5/html-author/ HTML 5 Reference] {{Webarchive|url=https://web.archive.org/web/20221126002559/https://html.spec.whatwg.org/multipage/ |date=26 November 2022 }}: "Although it is inspired by its SGML origins, in practice, it really only shares minor syntactic similarities. ... As HTML5 is no longer formally based upon SGML, the DOCTYPE no longer serves this purpose, and thus no longer needs to refer to a DTD."</ref> despite the similarity of its markup. It has, however, been designed to be backward-compatible with common parsing of older versions of HTML. It comes with a new introductory line that looks like an SGML [[Document type declaration|document type declaration]], <code style="white-space:nowrap;">&lt;!DOCTYPE html&gt;</code>, which triggers the standards-compliant [[Quirks mode|rendering mode]].<ref>{{cite web|first=Shannon |last=Suetos |date=26 April 2010 |url=http://www.instantshift.com/2010/04/26/html5-worth-the-hype/ |title=HTML5: Worth the Hype? |work=instantshift.com |access-date=21 October 2012}}</ref>
Since 5 January 2009, HTML5 also includes ''Web Forms 2.0'', a previously separate [[Organization:WHATWG|WHATWG]] specification.<ref>{{cite web|title=Web Forms 2.0|url=http://www.whatwg.org/specs/web-forms/current-work/|access-date=11 February 2014|date=5 January 2009}} obsolescence notice</ref><ref>{{cite web|url=http://www.whatwg.org/specs/web-apps/current-work/multipage/forms.html|title=HTML|work=whatwg.org}}</ref>

===New APIs===
[[File:HTML5 APIs and related technologies taxonomy and status.svg|thumb|420px|HTML5 related APIs<ref>Sergey Mavrody, ''Sergey's HTML5 & CSS3 Quick Reference'', 2nd ed. Belisso Corp., 2012. {{ISBN|978-0-9833867-2-8}}</ref>]]

In addition to specifying markup, HTML5 specifies scripting application programming interfaces (APIs) that can be used with [[JavaScript]].<ref name="html4-differences"/> Existing [[Document Object Model]] (DOM) interfaces are extended and ''de facto'' features documented. There are also new APIs, such as:
* [[Canvas element|Canvas]];<ref>{{cite web|url=http://www.syntaxxx.com/get-started-with-html5-canvas/|title=Get Started with HTM Canvas|website=syntaxxx.com|access-date=13 October 2014|archive-url=https://web.archive.org/web/20141018160105/http://www.syntaxxx.com/get-started-with-html5-canvas/|archive-date=18 October 2014|url-status=dead}}</ref>
* Timed Media Playback;<ref>{{cite web|url=https://html.spec.whatwg.org/multipage/embedded-content.html#media-elements|title=HTML|work=whatwg.org}}</ref>
* Offline;<ref>[https://www.w3.org/TR/offline-webapps/ "Offline Web Applications"] {{Webarchive|url=https://web.archive.org/web/20221126002556/https://www.w3.org/TR/offline-webapps/ |date=26 November 2022 }}. [[Organization:World Wide Web Consortium|World Wide Web Consortium]].</ref>
* Editable content;<ref>{{cite web|url=https://html.spec.whatwg.org/multipage/interaction.html#editing-2|title=HTML|work=whatwg.org}}</ref>
* [[Drag and drop]];<ref>{{cite web|url=https://html.spec.whatwg.org/multipage/interaction.html#dnd|title=HTML|work=whatwg.org}}</ref>
* History;<ref>{{cite web|url=https://www.w3.org/TR/html5/browsers.html#the-history-interface|title=The History interface|work=w3.org}}</ref>
* MIME type and protocol handler registration;<ref>{{cite web|url=https://html.spec.whatwg.org/multipage/embedded-content.html#mime-types|title=HTML|work=whatwg.org}}</ref><ref>{{cite web|url=https://html.spec.whatwg.org/multipage/webappapis.html#custom-handlers|title=HTML|work=whatwg.org}}</ref>
* [[Microdata (HTML)|Microdata]];<ref>{{cite web|url=https://html.spec.whatwg.org/multipage/microdata.html#microdata|title=HTML|work=whatwg.org}}</ref>
* [[Web Messaging]];<ref>{{cite web |url=https://html.spec.whatwg.org/multipage/web-messaging.html |title=Web Messaging specification |work=whatwg.org}}</ref>
* Web Storage&nbsp;– a key-value pair storage framework that provides behavior similar to cookies but with larger storage capacity and improved API.<ref>{{cite web |url=https://html.spec.whatwg.org/multipage/webstorage.html |title=Web Storage specification |work=whatwg.org}}</ref>

Not all of the above technologies are included in the W3C HTML5 specification, though they are in the WHATWG HTML specification.<ref>{{cite web|url=http://www.whatwg.org/specs/web-apps/current-work/multipage/introduction.html#is-this-html5 |title=1 Introduction – HTML Standard |publisher=Whatwg.org |access-date=8 January 2014}}</ref> Some related technologies, which are not part of either the W3C HTML5 or the WHATWG HTML specification, are as follows. The W3C publishes specifications for these separately:
* [[W3C Geolocation API|Geolocation]];
* IndexedDB&nbsp;– an indexed hierarchical key-value store (formerly WebSimpleDB);<ref>[https://www.w3.org/TR/IndexedDB/ "Indexed Database"] {{Webarchive|url=https://web.archive.org/web/20180302135346/http://www.w3.org/TR/IndexedDB/ |date=2 March 2018 }}. [[Organization:World Wide Web Consortium|World Wide Web Consortium]].</ref>
* [[HTML5 File API|File]]<ref>{{cite web|url=https://www.w3.org/TR/FileAPI/ |title=File API |publisher=W3.org |access-date=8 January 2014}}</ref>&nbsp;– an API intended to handle file uploads and file manipulation;<ref>[https://www.w3.org/TR/FileAPI/ "File API"] {{Webarchive|url=https://web.archive.org/web/20221126002556/https://www.w3.org/TR/FileAPI/ |date=26 November 2022 }}. [[Organization:World Wide Web Consortium|World Wide Web Consortium]].</ref>
* Directories and System&nbsp;– an API intended to satisfy client-side-storage use cases not well served by databases;<ref>[https://www.w3.org/TR/file-system-api/ "Filesystem API"] {{Webarchive|url=https://web.archive.org/web/20221126002556/https://www.w3.org/TR/file-system-api/ |date=26 November 2022 }}. [[Organization:World Wide Web Consortium|World Wide Web Consortium]].</ref>
* File Writer&nbsp;– an API for writing to files from web applications;<ref>[https://www.w3.org/TR/file-writer-api/ "File API: Writer"] {{Webarchive|url=https://web.archive.org/web/20221126002556/https://www.w3.org/TR/file-writer-api/ |date=26 November 2022 }}. [[Organization:World Wide Web Consortium|World Wide Web Consortium]].</ref>
* Web Audio<ref>{{cite web|url=https://www.w3.org/TR/webaudio/ |title=Web Audio API |publisher=[[Organization:World Wide Web Consortium|World Wide Web Consortium]] |access-date=2 March 2018}}</ref>&nbsp;– a high-level JavaScript API for processing and synthesizing audio in web applications;
* ClassList.<ref>{{cite web|url=https://developer.mozilla.org/en-US/docs/Web/API/element.classList|title=element.classList|author=MDN}}</ref>
* [[Web cryptography API]]<ref>{{cite web|url=https://www.w3.org/TR/WebCryptoAPI/|title=Web Cryptography API|website=w3.org}}</ref>
* [[Software:WebRTC|WebRTC]]<ref>{{cite web|url=https://www.w3.org/TR/webrtc/|title=WebRTC 1.0: Real-time Communication Between Browsers|website=w3.org|access-date=17 June 2016|archive-url=https://web.archive.org/web/20190407011412/http://www.w3.org/TR/webrtc/|archive-date=7 April 2019|url-status=dead}}</ref>
* [[Web SQL Database]]&nbsp;– a local [[SQL]] Database (no longer maintained);<ref>[https://www.w3.org/TR/webdatabase/ "Web SQL Database"] {{Webarchive|url=https://web.archive.org/web/20190203004924/http://www.w3.org/TR/webdatabase/ |date=3 February 2019 }}. [[Organization:World Wide Web Consortium|World Wide Web Consortium]].</ref>

HTML5 cannot provide animation within web pages. Additional JavaScript or CSS3 is necessary for animating HTML elements. Animation is also possible using JavaScript and HTML 4<ref>{{cite web|url=http://www.lynda.com/home/DisplayCourse.aspx?lpk2=67161|title=What HTML5 is (and what it isn't)|first=James|last=Williamson|year=2010|access-date=14 May 2014}}</ref>{{Failed verification|date=January 2011}}, and within SVG elements through [[Synchronized Multimedia Integration Language|SMIL]], although browser support of the latter remains uneven {{as of|2011|lc=y}}.

===XHTML5 (XML-serialized HTML5)<span class="anchor" id="XHTML 5 (XML-serialized HTML 5)"></span><span class="anchor" id="XHTML5"></span>===
XML documents must be served with an XML Internet media type (often called "MIME type") such as <code>application/xhtml+xml</code> or <code>application/xml</code>,<ref name="html4-differences">{{cite web|first1=Anne|last1=van Kesteren|first2=Simon|last2=Pieters|title=HTML5 differences from HTML4|url=https://html-differences.whatwg.org/#syntax|publisher= [[Organization:World Wide Web Consortium|World Wide Web Consortium]] |access-date=29 June 2017}}</ref> and must conform to strict, well-formed syntax of XML. XHTML5 is simply XML-serialized HTML5 data (that is, HTML5 constrained to XHTML's strict requirements, e.g., not having any unclosed tags), sent with one of XML media types. HTML that has been written to conform to both the HTML and XHTML specifications and therefore produces the same DOM tree whether parsed as HTML or XML is known as [[Polyglot markup|polyglot markup]].<ref name="w3c">{{cite web|last=Graff|first=Eliot|title=Polyglot Markup: HTML-Compatible XHTML Documents|url=https://www.w3.org/TR/html-polyglot/|publisher=W3C|access-date=6 July 2013}}</ref>

There is no DTD for XHTML5.<ref>{{cite web |title=14 The XML syntax |url=https://html.spec.whatwg.org/multipage/xhtml.html#xhtml |website=HTML Standard |publisher=WHATWG}}</ref>

===Error handling===
{{Cite check section|reason=<ref name="HTML5diffHTML4"/> only claims that HTML5 is Backward Compatible.|date=January 2024}} 
HTML5 is designed so that old browsers [[Forward compatibility|can safely ignore]] new HTML5 constructs.<ref name="HTML5diffHTML4"/> In contrast to HTML 4.01, the HTML5 specification gives detailed rules for lexing and [[Parsing|parsing]], with the intent that compliant browsers will produce the same results when parsing incorrect syntax.<ref name="whatfaq">{{cite web |url= https://github.com/whatwg/html/blob/main/FAQ.md#why-does-the-html-standard-legitimize-tag-soup |title=FAQ – WHATWG Wiki |access-date=26 August 2011 |work=WHATWG }}</ref> Although HTML5 now defines a consistent behavior for "[[Tag soup|tag soup]]" documents, those documents do not conform to the HTML5 standard.<ref name="whatfaq"/>

===Popularity===
According to a report released on 30 September 2011, 34 of the world's top 100 Web sites were using HTML5{{spaced ndash}}the adoption led by [[Search engine|search engine]]s and [[Social:Social network|social network]]s.<ref>{{cite web|title=Percentage of Web sites Using HTML5|date=30 September 2011|url=http://www.binvisions.com/articles/how-many-percentage-web-sites-using-html5|publisher=binvisions|access-date=21 October 2011}}</ref> Another report released in August 2013 has shown that 153 of the ''{{wipe|Fortune 500}}'' U.S. companies implemented HTML5 on their corporate websites.<ref>"[http://www.incore.com/Fortune500HTML5/#infographic HTML5 Popularity Among Fortune 500 Companies] {{Webarchive|url=https://web.archive.org/web/20170614024615/http://www.incore.com/Fortune500HTML5/#infographic |date=14 June 2017 }}". INCORE. Retrieved 5 March 2013.</ref>

Since 2014, HTML5 is at least partially supported by most popular layout engines.

===Differences from HTML&nbsp;4.01 and XHTML&nbsp;1.x===
The following is a cursory list of differences and some specific examples.
* New parsing rules: oriented towards flexible parsing and compatibility; not based on SGML
* Ability to use inline SVG and MathML in <code>text/html</code>
* New elements: <code>article</code>, <code>aside</code>, <code>audio</code>, <code>bdi</code>, <code>canvas</code>, <code>command</code>, <code>data</code>, <code>datalist</code>, <code>details</code>, <code>embed</code>, <code>figcaption</code>, <code>figure</code>, <code>footer</code>, <code>header</code>, <code>keygen</code>, <code>mark</code>, <code>meter</code>, <code>nav</code>, <code>output</code>, <code>progress</code>, <code>rp</code>, <code>rt</code>, <code>[[Ruby character#HTML|ruby]]</code>, <code>section</code>, <code>source</code>, <code>summary</code>, <code>time</code>, <code>track</code>, <code>video</code>, <code>wbr</code>
* New types of form controls: <code>dates and times</code>, <code>email</code>, <code>url</code>, <code>search</code>, <code>number</code>, <code>range</code>, <code>tel</code>, <code>color</code><ref>{{cite web|url=http://www.w3.org/wiki/HTML5_form_additions |title=HTML5 form additions |publisher= [[Organization:World Wide Web Consortium|World Wide Web Consortium]] |access-date=13 October 2014}}</ref>
* New attributes: <code>charset</code> (on <code>meta</code>), <code>async</code> (on <code>script</code>)
* Global attributes (that can be applied for every element): <code>id</code>, <code>tabindex</code>, <code>hidden</code>, <code>data-*</code> (custom data attributes)
* Deprecated elements will be dropped altogether: <code>acronym</code>, <code>applet</code>, <code>basefont</code>, <code>big</code>, <code>center</code>, <code>dir</code>, <code>font</code>, <code>frame</code>, [[Framing (World Wide Web)|<code>frameset</code>]], <code>isindex</code>, <code>noframes</code>, <code>strike</code>, <code>tt</code>

W3C Working Group publishes "HTML5 differences from HTML 4",<ref>{{cite web
|url=https://www.w3.org/TR/html5-diff/
|title=HTML5 Differences from HTML4
|work=FAQ
|publisher= [[Organization:World Wide Web Consortium|World Wide Web Consortium]]
|date=9 December 2014
|access-date=2 March 2018}}</ref> which provides a complete outline of additions, removals and changes between HTML5 and HTML4.

==Logo==
[[File:HTML5-logo.svg|thumb|120px|The W3C HTML5 logo]]
On 18 January 2011, the W3C introduced a logo to represent the use of or interest in HTML5. Unlike other badges previously issued by the W3C, it does not imply validity or conformance to a certain standard. As of 1 April 2011, this logo is official.<ref name="logo-faq">{{cite web | url = https://www.w3.org/html/logo/faq.html | title = W3C HTML5 Logo FAQ | publisher = [[Organization:World Wide Web Consortium|World Wide Web Consortium]] | access-date =21 January 2011 |quote = Is this W3C's "official" logo for HTML5? Yes, as of 1 April 2011.}}</ref>
<!--Should there be a reference to state when and how the logo may be used?-->

When initially presenting it to the public, the W3C announced the HTML5 logo as a "general-purpose visual identity for a broad set of open web technologies, including HTML5, [[Cascading Style Sheets|CSS]], SVG, [[Web Open Font Format|WOFF]], and others".<ref name="waspopenletter">{{cite web | url = http://www.webstandards.org/2011/01/18/regarding-the-html5-logo | title = HTML5 Logo: Be Proud, But Don't Muddy the Waters! | publisher = The Web Standards Project | access-date = 22 January 2011 | archive-url = https://web.archive.org/web/20110810064604/http://www.webstandards.org/2011/01/18/regarding-the-html5-logo/ | archive-date = 10 August 2011 | url-status = dead }}</ref> Some web standard advocates, including The Web Standards Project, criticized that definition of "HTML5" as an umbrella term, pointing out the blurring of terminology and the potential for miscommunication.<ref name="waspopenletter" /> Three days later, the W3C responded to community feedback and changed the logo's definition, dropping the enumeration of related technologies.<ref>{{cite web | url = https://www.w3.org/blog/2011/01/the-html5-logo-conversation/ | title = The HTML5 Logo Conversation | publisher = World Wide Web Consortium | access-date =21 January 2011 }}</ref> The W3C then said the logo "represents HTML5, the cornerstone for modern Web applications".<ref name="logo-faq" />

==Digital rights management==
Industry players including the BBC, Google, [[Company:Microsoft|Microsoft]], [[Company:Apple Inc.|Apple Inc.]] have been lobbying for the inclusion of [[Encrypted Media Extensions]] (EME),<ref>[https://w3c.github.io/encrypted-media/ Encrypted Media Extensions] {{Webarchive|url=https://web.archive.org/web/20210120213149/https://w3c.github.io/encrypted-media/ |date=20 January 2021 }} draft specification of the W3C</ref><ref>{{cite web
 |title=Netflix coming to HTML5 just as soon as the DRM ducks are in a row
 |url=https://arstechnica.com/information-technology/2013/04/netflix-coming-to-html5-just-as-soon-as-the-drm-ducks-are-in-a-row/
 |publisher=Ars Technica
 |date=16 April 2013
 |first=Peter
|last=Bright
}}</ref><ref>{{cite web
 |title=DRM in HTML5
 |url=http://manu.sporny.org/2013/drm-in-html5/
 |date=26 January 2013
 |first=Manu
|last=Sporny
}}</ref><ref>{{cite web
 |title=Tell W3C: We don't want the Hollyweb
 |url=https://www.defectivebydesign.org/no-drm-in-html5
 |publisher=[[Organization:Free Software Foundation|Free Software Foundation]]
 |date=May 2013
}}</ref><ref>{{cite web
 |title=HTML5 webpage locks 'would stifle innovation'
 |url=https://www.bbc.co.uk/news/technology-22714209
 |publisher=BBC News
 |date=30 May 2013
}}</ref> a form of [[Engineering:Digital rights management|digital rights management]] (DRM), into the HTML5 standard. As of the end of 2012 and the beginning of 2013, 27 organizations<ref>{{cite web|title=Une coalition de vingt-sept organisations demande au W3C de garder les menottes numériques (DRM) hors des standards du Web|url=http://www.april.org/une-coalition-de-vingt-sept-organisations-demande-au-w3c-de-garder-les-menottes-numeriques-drm-hors|date=24 April 2013|access-date=14 May 2014}}</ref> including the [[Organization:Free Software Foundation|Free Software Foundation]]<ref>{{cite web|url=http://www.defectivebydesign.org/no-drm-in-html5|title=Tell W3C: We don't want the Hollyweb – Free Software Foundation|website=defectivebydesign.org|access-date=6 May 2013|archive-url=https://web.archive.org/web/20130403124524/http://www.defectivebydesign.org/no-drm-in-html5|archive-date=3 April 2013|url-status=dead}}</ref> have started a campaign against including digital rights management in the HTML5 standard.<ref>{{cite web|title=The W3C's Soul at Stake|url=http://www.fsf.org/blogs/rms/w3c-soul-at-stake|first=Richard|last=Stallman|publisher=The Free Software Foundation|date=2 May 2013|access-date=14 May 2014}}</ref><ref>{{cite web|title=Netflix Wants to Go HTML5, but Not Without DRM|url=http://news.slashdot.org/story/13/04/16/1228245/netflix-wants-to-go-html5-but-not-without-drm|first=Timothy|last=Lord|date=16 April 2013|access-date=14 May 2014}}</ref> However, in late September 2013, the W3C [[HTML Working Group]] decided that Encrypted Media Extensions, a form of DRM, was "in scope" and will potentially be included in the HTML 5.1 standard.<ref>{{cite web|url=http://lists.w3.org/Archives/Public/public-html-admin/2013Sep/0129.html |title=New Charter for the HTML Working Group from Philippe Le Hegaret on 2013-09-30 (public-html-admin@w3.org from September 2013) |publisher=Lists.w3.org |date=30 September 2013 |access-date=8 January 2014}}</ref><ref name="lowering-your-standards">{{cite web
 | url     = https://www.eff.org/deeplinks/2013/10/lowering-your-standards
 | title    = Lowering Your Standards: DRM and the Future of the W3C
 | first   = Danny
 | last   = O'Brien
 | publisher  = [[Organization:Electronic Frontier Foundation|Electronic Frontier Foundation]]
 | date    = 2 October 2013
 | access-date = 3 October 2013
}}</ref> [[Organization:WHATWG|WHATWG]]'s "HTML Living Standard" continued to be developed without DRM-enabled proposals.<ref name="lowering-your-standards"/>

Manu Sporny, a member of the W3C, said that EME would not solve the problem it was supposed to address.<ref>{{cite web
 | url      = http://manu.sporny.org/2013/drm-in-html5/
 | title     = DRM in HTML5
 | first    = Manu
 | last    = Sporny
 | work     = The Beautiful, Tormented Machine
 | publisher   = Manu Sporny
 | date     = 26 January 2013
 | access-date  = 16 May 2014
 | archive-url  = https://web.archive.org/web/20140425044032/http://manu.sporny.org/2013/drm-in-html5/
 | archive-date=25 April 2014<!-- 2014-04-25 04:40:32-->
}}</ref>
Opponents point out that EME itself is just an architecture for a DRM plug-in mechanism.<ref>{{cite web
 |url         = http://www.webmonkey.com/2013/02/drm-for-the-web-say-it-aint-so/
 |title       = DRM for the Web? Say It Ain't So
 |first      = Scott
 |last      = Gilbertson
 |work        = Webmonkey
 |date        = 12 February 2013
 |access-date  = 21 March 2013
 |archive-url  = https://web.archive.org/web/20130324134750/http://www.webmonkey.com/2013/02/drm-for-the-web-say-it-aint-so
 |archive-date = 24 March 2013
 |url-status  = dead
}}</ref>

The initial enablers for DRM in HTML5 were Google<ref>{{cite web
 | url = http://googlechromereleases.blogspot.be/2013/02/stable-channel-update-for-chrome-os_21.html
 | title = Release notes for Google Chrome 25.0.1364.87
}}</ref> and Microsoft.<ref>{{cite web
 | url = http://techblog.netflix.com/2013/06/html5-video-in-ie-11-on-windows-81.html
 | title = HTML5 Video in IE 11 on Windows 8.1
| date = 18 April 2017
}}</ref> Supporters also include Adobe.<ref>[https://blogs.adobe.com/standards/2013/06/19/adobe-support-for-encrypted-media-extensions/ Adobe Support for Encrypted Media Extensions] {{Webarchive|url=https://web.archive.org/web/20161109050937/https://blogs.adobe.com/standards/2013/06/19/adobe-support-for-encrypted-media-extensions/ |date=9 November 2016 }} Adobe.com. 19 June 2013.</ref> On 14 May 2014, [[Organization:Mozilla Foundation|Mozilla]] announced plans to support EME in [[Software:Firefox|Firefox]], the last major browser to avoid DRM.<ref name="gal">{{cite web|url=https://hacks.mozilla.org/2014/05/reconciling-mozillas-mission-and-w3c-eme/|title=Reconciling Mozilla's Mission and W3C EME|first=Andreas|last=Gal|publisher=Mozilla|date=14 May 2014|access-date=20 May 2014}}</ref><ref name="baker">{{cite web|url=https://blog.mozilla.org/blog/2014/05/14/drm-and-the-challenge-of-serving-users/|title=DRM and the Challenge of Serving Users|first=Mitchell|last=Baker|publisher=Mozilla|date=14 May 2014|access-date=20 May 2014}}</ref> Calling it "a difficult and uncomfortable step", Andreas Gal of Mozilla explained that future versions of Firefox would remain open source but ship with a sandbox designed to run a content decryption module developed by Adobe,<ref name="gal" /> later it was replaced with [[Software:Widevine|Widevine]] module from [[Company:Google|Google]] which is much more widely adopted by content providers. While promising to "work on alternative solutions", Mozilla's Executive Chair Mitchell Baker stated that a refusal to implement EME would have accomplished little more than convincing many users to switch browsers.<ref name="baker" /> This decision was condemned by Cory Doctorow and the [[Organization:Free Software Foundation|Free Software Foundation]].<ref>{{cite web|url=https://www.theguardian.com/technology/2014/may/14/firefox-closed-source-drm-video-browser-cory-doctorow|title=Firefox's adoption of closed-source DRM breaks my heart|first=Cory|last=Doctorow|work=The Guardian|date=14 May 2014|access-date=20 May 2014}}</ref><ref>{{cite web|url=https://fsf.org/news/fsf-condemns-partnership-between-mozilla-and-adobe-to-support-digital-restrictions-management|title=FSF condemns partnership between Mozilla and Adobe to support Digital Rights Management|publisher=Free Software Foundation|date=14 May 2014|access-date=20 May 2014}}</ref>

As of December 2023, the [[Organization:World Wide Web Consortium|W3C]] has changed their opinion on [[Encrypted Media Extensions|EME]], stating: "Encrypted Media Extensions (EME) brings greater interoperability, better privacy, security, accessibility and user experience in viewing movies and TV on the Web".<ref>{{Cite web |date=2017-09-18 |title=W3C Publishes Encrypted Media Extensions (EME) as a W3C Recommendation |url=https://www.w3.org/press-releases/2017/eme-recommendation/ |access-date=2023-12-09 |website=W3C |language=en}}</ref>

==See also==
* [[Cache manifest in HTML5]]
* [[Canvas element]]
* Dave Hyatt, Apple's editor of HTML5 specs
* Ian Hickson, Google's main editor of HTML5 specs
* [[Polyglot markup]]

==References==
{{Reflist}}

==External links==
* [https://html.spec.whatwg.org/multipage/ HTML Living standard from WHATWG], GitHub [https://github.com/whatwg/html repo]
* [https://validator.w3.org The W3C Markup Validation Service], including Nu Html Checker
* [https://www.w3.org/TR/2017/REC-html52-20171214/ HTML 5.2], the last HTML recommendation from W3C, superseded
* [https://www.w3.org/2021/06/WHATWG-W3C-MOU_2021_update.html Memorandum of Understanding Between W3C and WHATWG]
* [https://www.w3.org/html/wg/ HTML Media Extensions Working Group]
* [https://www.w3.org/Bugs/Public/buglist.cgi?product=HTML.next HTML.next], Feature requests for future versions of HTML

{{Web browsers|fsp}}
{{W3C Standards}}

{{DEFAULTSORT:Html 5}}
[[Category:HTML5| ]]
[[Category:XML-based standards]]

{{Sourceattribution|HTML5}}