HTML5

"Thoughts on Flash"

While some features of HTML5 are often compared to Adobe Flash, the two technologies are very different. Both include features for playing audio and video within web pages, and for using vector graphics. However, HTML5 on its own cannot be used for animation or interactivity – 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^{[17][18][19][20]} after Apple Inc.'s then-CEO 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".^[21] 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.^[22] In early November 2011, Adobe announced that it would discontinue the development of the Flash Player browser plugin for mobile devices and reorient its efforts in developing tools using HTML5.^[23] On 25 July 2017, Adobe announced that both the distribution and support of Flash would cease by the end of 2020.^[24] 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.^[25]

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.^[26] In January 2011, the WHATWG renamed its "HTML5" specification HTML Living Standard. The W3C nevertheless continued its project to release HTML5.^[27]

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.^[28]

In December 2012, W3C designated HTML5 as a Candidate Recommendation.^[29] The criterion for advancement to W3C Recommendation is "two 100% complete and fully interoperable implementations".^[30]

On 16 September 2014, W3C moved HTML5 to Proposed Recommendation.^[31] On 28 October 2014, HTML5 was released as a W3C Recommendation,^[32] bringing the specification process to completion.^[5] On 1 November 2016, HTML 5.1 was released as a W3C Recommendation.^[33] On 14 December 2017, HTML 5.2 was released as a W3C Recommendation.^[34]

Retirement

The W3C retired HTML5 on 27 March 2018.^[35] Additionally, the retirement included HTML 4.0,^[36] HTML 4.01,^[37] XHTML 1.0,^[38] and XHTML 1.1.^[39] HTML 5.1, HTML 5.2 and HTML 5.3 were all retired on 28 January 2021, in favour of the HTML living standard.^[3][40]

Timeline

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

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.^{[45][46][47][4]} 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,^[11] and yet also at cross purposes^[28][5] 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",^[48] and characterized by "squabbling".^[5]

In at least one case, namely the permissible content of the <cite> element, the two specifications directly contradicted each other (as of July 2018),^[update] with the W3C definition allowing a broader range of uses than the WHATWG definition.^[49][50]

The "Introduction" section in the WHATWG spec (edited by Ian "Hixie" Hickson) is critical of W3C, e.g. "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:^[51]

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.

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).

The two entities signed an agreement to work together on a single version of HTML on 28 May 2019.^[52]

Markup

HTML5 introduces elements and attributes that reflect typical usage on modern websites. Some of them are semantic replacements for common uses of generic block (<div>) and inline (<span>) elements, for example <nav> (website navigation block), <footer> (usually referring to bottom of web page or to last lines of HTML code), or <audio> and <video> instead of <object>.^[90][91][92] Some deprecated elements from HTML 4.01 have been dropped, including purely presentational elements such as <font> and <center>, whose effects have long been superseded by the more capable Cascading Style Sheets.^[93] There is also a renewed emphasis on the importance of client-side JavaScript used to create dynamic web pages.^{[citation needed]}

The HTML5 syntax is no longer based on SGML^[94][95] 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, <!DOCTYPE html>, which triggers the standards-compliant rendering mode.^[96] Since 5 January 2009, HTML5 also includes Web Forms 2.0, a previously separate WHATWG specification.^[97][98]

New APIs

In addition to specifying markup, HTML5 specifies scripting application programming interfaces (APIs) that can be used with JavaScript.^[100] Existing Document Object Model (DOM) interfaces are extended and de facto features documented. There are also new APIs, such as:

• Canvas;^[101]
• Timed Media Playback;^[102]
• Offline;^[103]
• Editable content;^[104]
• Drag and drop;^[105]
• History;^[106]
• MIME type and protocol handler registration;^[107][108]
• Microdata;^[109]
• Web Messaging;^[110]
• Web Storage – a key-value pair storage framework that provides behavior similar to cookies but with larger storage capacity and improved API.^[111]

Not all of the above technologies are included in the W3C HTML5 specification, though they are in the WHATWG HTML specification.^[112] 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:

• Geolocation;
• IndexedDB – an indexed hierarchical key-value store (formerly WebSimpleDB);^[113]
• File^[114] – an API intended to handle file uploads and file manipulation;^[115]
• Directories and System – an API intended to satisfy client-side-storage use cases not well served by databases;^[116]
• File Writer – an API for writing to files from web applications;^[117]
• Web Audio^[118] – a high-level JavaScript API for processing and synthesizing audio in web applications;
• ClassList.^[119]
• Web cryptography API^[120]
• WebRTC^[121]
• Web SQL Database – a local SQL Database (no longer maintained);^[122]

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^{[123][failed verification]}, and within SVG elements through SMIL, although browser support of the latter remains uneven as of 2011^[update].

XHTML5 (XML-serialized HTML5)

XML documents must be served with an XML Internet media type (often called "MIME type") such as application/xhtml+xml or application/xml,^[100] 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.^[124]

There is no DTD for XHTML5.^[125]

Warning! Using the XML syntax is not recommended, for reasons which include the fact that there is no specification which defines the rules for how an XML parser must map a string of bytes or characters into a Document object, as well as the fact that the XML syntax is essentially unmaintained — in that, it’s not expected that any further features will ever be added to the XML syntax (even when such features have been added to the HTML syntax).

Error handling

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HTML5 is designed so that old browsers can safely ignore new HTML5 constructs.^[8] In contrast to HTML 4.01, the HTML5 specification gives detailed rules for lexing and parsing, with the intent that compliant browsers will produce the same results when parsing incorrect syntax.^[126] Although HTML5 now defines a consistent behavior for "tag soup" documents, those documents do not conform to the HTML5 standard.^[126]

Popularity

According to a report released on 30 September 2011, 34 of the world's top 100 Web sites were using HTML5 – the adoption led by search engines and social networks.^[127] Another report released in August 2013 has shown that 153 of the Fortune 500 U.S. companies implemented HTML5 on their corporate websites.^[128]

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

Differences from HTML 4.01 and XHTML 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 text/html
• New elements: article, aside, audio, bdi, canvas, command, data, datalist, details, embed, figcaption, figure, footer, header, keygen, mark, meter, nav, output, progress, rp, rt, ruby, section, source, summary, time, track, video, wbr
• New types of form controls: dates and times, email, url, search, number, range, tel, color^[129]
• New attributes: charset (on meta), async (on script)
• Global attributes (that can be applied for every element): id, tabindex, hidden, data-* (custom data attributes)
• Deprecated elements will be dropped altogether: acronym, applet, basefont, big, center, dir, font, frame, frameset, isindex, noframes, strike, tt

W3C Working Group publishes "HTML5 differences from HTML 4",^[130] which provides a complete outline of additions, removals and changes between HTML5 and HTML4.