HTML: The Living Standard

Edition for Web Developers — Last Updated 29 October 2024

1. 3 Semantics, structure, and APIs of HTML documents
   1. 3.1 Documents
      1. 3.1.1 The Document object
      2. 3.1.2 The DocumentOrShadowRoot interface
      3. 3.1.3 Resource metadata management
      4. 3.1.4 Reporting document loading status
      5. 3.1.5 Render-blocking mechanism
      6. 3.1.6 DOM tree accessors
   2. 3.2 Elements
      1. 3.2.1 Semantics
      2. 3.2.2 Elements in the DOM
      3. 3.2.3 Element definitions
         1. 3.2.3.1 Attributes
      4. 3.2.4 Content models
         1. 3.2.4.1 The "nothing" content model
         2. 3.2.4.2 Kinds of content
            1. 3.2.4.2.1 Metadata content
            2. 3.2.4.2.2 Flow content
            3. 3.2.4.2.3 Sectioning content
            4. 3.2.4.2.4 Heading content
            5. 3.2.4.2.5 Phrasing content
            6. 3.2.4.2.6 Embedded content
            7. 3.2.4.2.7 Interactive content
            8. 3.2.4.2.8 Palpable content
            9. 3.2.4.2.9 Script-supporting elements
         3. 3.2.4.3 Transparent content models
         4. 3.2.4.4 Paragraphs
      5. 3.2.5 Global attributes
         1. 3.2.5.1 The title attribute
         2. 3.2.5.2 The lang and xml:lang attributes
         3. 3.2.5.3 The translate attribute
         4. 3.2.5.4 The dir attribute
         5. 3.2.5.5 The style attribute
         6. 3.2.5.6 Embedding custom non-visible data with the data-* attributes
      6. 3.2.6 The innerText and outerText properties
      7. 3.2.7 Requirements relating to the bidirectional algorithm

3 Semantics, structure, and APIs of HTML documents

3.1 Documents

Every XML and HTML document in an HTML UA is represented by a Document object. [DOM]

The Document object's URL is defined in DOM. It is initially set when the Document object is created, but can change during the lifetime of the Document object; for example, it changes when the user navigates to a fragment on the page and when the pushState() method is called with a new URL. [DOM]

Interactive user agents typically expose the Document object's URL in their user interface. This is the primary mechanism by which a user can tell if a site is attempting to impersonate another.

The Document object's origin is defined in DOM. It is initially set when the Document object is created, and can change during the lifetime of the Document only upon setting document.domain. A Document's origin can differ from the origin of its URL; for example when a child navigable is created, its active document's origin is inherited from its parent's active document's origin, even though its active document's URL is about:blank. [DOM]

When a Document is created by a script using the createDocument() or createHTMLDocument() methods, the Document is ready for post-load tasks immediately.

The document's referrer is a string (representing a URL) that can be set when the Document is created. If it is not explicitly set, then its value is the empty string.

3.1.1 The Document object

DOM defines a Document interface, which this specification extends significantly.

Each Document has a policy container (a policy container), initially a new policy container, which contains policies which apply to the Document.

Each Document has a permissions policy, which is a permissions policy, which is initially empty.

Each Document has a module map, which is a module map, initially empty.

Each Document has an opener policy, which is an opener policy, initially a new opener policy.

Each Document has an is initial about:blank, which is a boolean, initially false.

Each Document has a during-loading navigation ID for WebDriver BiDi, which is a navigation ID or null, initially null.

As the name indicates, this is used for interfacing with the WebDriver BiDi specification, which needs to be informed about certain occurrences during the early parts of the Document's lifecycle, in a way that ties them to the original navigation ID used when the navigation that created this Document was the ongoing navigation. This eventually gets set back to null, after WebDriver BiDi considers the loading process to be finished. [BIDI]

Each Document has an about base URL, which is a URL or null, initially null.

This is only populated for "about:"-schemed Documents.

Each Document has a bfcache blocking details, which is a set of not restored reason details, initially empty.

3.1.2 The DocumentOrShadowRoot interface

DOM defines the DocumentOrShadowRoot mixin, which this specification extends.

3.1.3 Resource metadata management

document.referrer

Returns the URL of the Document from which the user navigated to this one, unless it was blocked or there was no such document, in which case it returns the empty string.

The noreferrer link type can be used to block the referrer.

document.cookie [ = value ]

✔MDN

Document/cookie

Support in all current engines.

Firefox1+Safari1+Chrome1+

---

Opera3+Edge79+

---

Edge (Legacy)12+Internet Explorer4+

---

Firefox Android?Safari iOS?Chrome Android?WebView Android?Samsung Internet?Opera Android10.1+

Returns the HTTP cookies that apply to the Document. If there are no cookies or cookies can't be applied to this resource, the empty string will be returned.

Can be set, to add a new cookie to the element's set of HTTP cookies.

If the contents are sandboxed into an opaque origin (e.g., in an iframe with the sandbox attribute), a "SecurityError" DOMException will be thrown on getting and setting.

document.lastModified

Returns the date of the last modification to the document, as reported by the server, in the form "MM/DD/YYYY hh:mm:ss", in the user's local time zone.

If the last modification date is not known, the current time is returned instead.

3.1.4 Reporting document loading status

document.readyState

Returns "loading" while the Document is loading, "interactive" once it is finished parsing but still loading subresources, and "complete" once it has loaded.

The readystatechange event fires on the Document object when this value changes.

The DOMContentLoaded event fires after the transition to "interactive" but before the transition to "complete", at the point where all subresources apart from async script elements have loaded.

3.1.5 Render-blocking mechanism

Each Document has a render-blocking element set, a set of elements, initially the empty set.

A Document document allows adding render-blocking elements if document's content type is "text/html" and the body element of document is null.

A Document document is render-blocked if both of the following are true:

• document's render-blocking element set is non-empty, or document allows adding render-blocking elements.

• The current high resolution time given document's relevant global object has not exceeded an implementation-defined timeout value.

An element el is render-blocking if el's node document document is render-blocked, and el is in document's render-blocking element set.

To block rendering on an element el:

1. Let document be el's node document.

2. If document allows adding render-blocking elements, then append el to document's render-blocking element set.

To unblock rendering on an element el:

1. Let document be el's node document.

2. Remove el from document's render-blocking element set.

Whenever a render-blocking element el becomes browsing-context disconnected, or el's blocking attribute's value is changed so that el is no longer potentially render-blocking, then unblock rendering on el.

3.1.6 DOM tree accessors

The html element of a document is its document element, if it's an html element, and null otherwise.

document.head

Returns the head element.

The head element of a document is the first head element that is a child of the html element, if there is one, or null otherwise.

document.title [ = value ]

Returns the document's title, as given by the title element for HTML and as given by the SVG title element for SVG.

Can be set, to update the document's title. If there is no appropriate element to update, the new value is ignored.

The title element of a document is the first title element in the document (in tree order), if there is one, or null otherwise.

document.body [ = value ]

Returns the body element.

Can be set, to replace the body element.

If the new value is not a body or frameset element, this will throw a "HierarchyRequestError" DOMException.

The body element of a document is the first of the html element's children that is either a body element or a frameset element, or null if there is no such element.

document.images

Returns an HTMLCollection of the img elements in the Document.

document.embeds

document.plugins

Returns an HTMLCollection of the embed elements in the Document.

document.links

Returns an HTMLCollection of the a and area elements in the Document that have href attributes.

document.forms

Returns an HTMLCollection of the form elements in the Document.

document.scripts

Returns an HTMLCollection of the script elements in the Document.

collection = document.getElementsByName(name)

Returns a NodeList of elements in the Document that have a name attribute with the value name.

document.currentScript

Returns the script element, or the SVG script element, that is currently executing, as long as the element represents a classic script. In the case of reentrant script execution, returns the one that most recently started executing amongst those that have not yet finished executing.

Returns null if the Document is not currently executing a script or SVG script element (e.g., because the running script is an event handler, or a timeout), or if the currently executing script or SVG script element represents a module script.

This API has fallen out of favor in the implementer and standards community, as it globally exposes script or SVG script elements. As such, it is not available in newer contexts, such as when running module scripts or when running scripts in a shadow tree. We are looking into creating a new solution for identifying the running script in such contexts, which does not make it globally available: see issue #1013.

The dir attribute on the Document interface is defined along with the dir content attribute.

3.2 Elements

3.2.1 Semantics

Elements, attributes, and attribute values in HTML are defined (by this specification) to have certain meanings (semantics). For example, the ol element represents an ordered list, and the lang attribute represents the language of the content.

These definitions allow HTML processors, such as web browsers or search engines, to present and use documents and applications in a wide variety of contexts that the author might not have considered.

<!DOCTYPE HTML>
<html lang="en">
 <head>
  <title>My Page</title>
 </head>
 <body>
  <h1>Welcome to my page</h1>
  <p>I like cars and lorries and have a big Jeep!</p>
  <h2>Where I live</h2>
  <p>I live in a small hut on a mountain!</p>
 </body>
</html>

Authors must not use elements, attributes, or attribute values for purposes other than their appropriate intended semantic purpose, as doing so prevents software from correctly processing the page.

<body>
 <h1>ACME Corporation</h1>
 <h2>The leaders in arbitrary fast delivery since 1920</h2>
 ...

<body>
 <hgroup>
  <h1>ACME Corporation</h1>
  <p>The leaders in arbitrary fast delivery since 1920</p>
 </hgroup>
 ...

<!DOCTYPE HTML>
<html lang="en-GB">
 <head> <title> Demonstration </title> </head>
 <body>
  <table>
   <tr> <td> My favourite animal is the cat. </td> </tr>
   <tr>
    <td>
     —<a href="https://example.org/~ernest/"><cite>Ernest</cite></a>,
     in an essay from 1992
    </td>
   </tr>
  </table>
 </body>
</html>

<!DOCTYPE HTML>
<html lang="en-GB">
 <head> <title> Demonstration </title> </head>
 <body>
  <blockquote>
   <p> My favourite animal is the cat. </p>
  </blockquote>
  <p>
   —<a href="https://example.org/~ernest/">Ernest</a>,
   in an essay from 1992
  </p>
 </body>
</html>

Authors must not use elements, attributes, or attribute values that are not permitted by this specification or other applicable specifications, as doing so makes it significantly harder for the language to be extended in the future.

<label>Carpet: <input type="carpet" name="c" texture="deep pile"></label>

<label>Carpet: <input type="text" class="carpet" name="c" data-texture="deep pile"></label>

DOM nodes whose node document's browsing context is null are exempt from all document conformance requirements other than the HTML syntax requirements and XML syntax requirements.

<template>
 <article>
  <img src="{{src}}" alt="{{alt}}">
  <h1></h1>
 </article>
</template>

Through scripting and using other mechanisms, the values of attributes, text, and indeed the entire structure of the document may change dynamically while a user agent is processing it. The semantics of a document at an instant in time are those represented by the state of the document at that instant in time, and the semantics of a document can therefore change over time. User agents update their presentation of the document as this occurs.

HTML has a progress element that describes a progress bar. If its "value" attribute is dynamically updated by a script, the UA would update the rendering to show the progress changing.

3.2.2 Elements in the DOM

The nodes representing HTML elements in the DOM implement, and expose to scripts, the interfaces listed for them in the relevant sections of this specification. This includes HTML elements in XML documents, even when those documents are in another context (e.g. inside an XSLT transform).

Elements in the DOM represent things; that is, they have intrinsic meaning, also known as semantics.

For example, an ol element represents an ordered list.

Elements can be referenced (referred to) in some way, either explicitly or implicitly. One way that an element in the DOM can be explicitly referenced is by giving an id attribute to the element, and then creating a hyperlink with that id attribute's value as the fragment for the hyperlink's href attribute value. Hyperlinks are not necessary for a reference, however; any manner of referring to the element in question will suffice.

<figure id="module-script-graph">
  <img src="module-script-graph.svg"
       alt="Module A depends on module B, which depends
            on modules C and D.">
  <figcaption>Figure 27: a simple module graph</figcaption>
</figure>

As we can see in <a href="#module-script-graph">figure 27</a>, ...

The basic interface, from which all the HTML elements' interfaces inherit, is the HTMLElement interface.

The HTMLElement interface holds methods and attributes related to a number of disparate features, and the members of this interface are therefore described in various different sections of this specification.

const el = document.createElementNS("some namespace", "example");
console.assert(el.constructor === Element);

3.2.3 Element definitions

Each element in this specification has a definition that includes the following information:

Categories

A list of categories to which the element belongs. These are used when defining the content models for each element.

Contexts in which this element can be used

A non-normative description of where the element can be used. This information is redundant with the content models of elements that allow this one as a child, and is provided only as a convenience.

For simplicity, only the most specific expectations are listed.

For example, all phrasing content is flow content. Thus, elements that are phrasing content will only be listed as "where phrasing content is expected", since this is the more-specific expectation. Anywhere that expects flow content also expects phrasing content, and thus also meets this expectation.

Content model

A normative description of what content must be included as children and descendants of the element.

Tag omission in text/html

A non-normative description of whether, in the text/html syntax, the start and end tags can be omitted. This information is redundant with the normative requirements given in the optional tags section, and is provided in the element definitions only as a convenience.

Content attributes

A normative list of attributes that may be specified on the element (except where otherwise disallowed), along with non-normative descriptions of those attributes. (The content to the left of the dash is normative, the content to the right of the dash is not.)

Accessibility considerations

For authors: Conformance requirements for use of ARIA role and aria-* attributes are defined in ARIA in HTML. [ARIA] [ARIAHTML]

For implementers: User agent requirements for implementing accessibility API semantics are defined in HTML Accessibility API Mappings. [HTMLAAM]

DOM interface

A normative definition of a DOM interface that such elements must implement.

This is then followed by a description of what the element represents, along with any additional normative conformance criteria that may apply to authors. Examples are sometimes also included.

3.2.3.1 Attributes

An attribute value is a string. Except where otherwise specified, attribute values on HTML elements may be any string value, including the empty string, and there is no restriction on what text can be specified in such attribute values.

3.2.4 Content models

Each element defined in this specification has a content model: a description of the element's expected contents. An HTML element must have contents that match the requirements described in the element's content model. The contents of an element are its children in the DOM.

ASCII whitespace is always allowed between elements. User agents represent these characters between elements in the source markup as Text nodes in the DOM. Empty Text nodes and Text nodes consisting of just sequences of those characters are considered inter-element whitespace.

Inter-element whitespace, comment nodes, and processing instruction nodes must be ignored when establishing whether an element's contents match the element's content model or not, and must be ignored when following algorithms that define document and element semantics.

Thus, an element A is said to be preceded or followed by a second element B if A and B have the same parent node and there are no other element nodes or Text nodes (other than inter-element whitespace) between them. Similarly, a node is the only child of an element if that element contains no other nodes other than inter-element whitespace, comment nodes, and processing instruction nodes.

Authors must not use HTML elements anywhere except where they are explicitly allowed, as defined for each element, or as explicitly required by other specifications. For XML compound documents, these contexts could be inside elements from other namespaces, if those elements are defined as providing the relevant contexts.

The Atom Syndication Format defines a content element. When its type attribute has the value xhtml, The Atom Syndication Format requires that it contain a single HTML div element. Thus, a div element is allowed in that context, even though this is not explicitly normatively stated by this specification. [ATOM]

In addition, HTML elements may be orphan nodes (i.e. without a parent node).

var data = {
  name: "Banana",
  cell: document.createElement('td'),
};

3.2.4.1 The "nothing" content model

When an element's content model is nothing, the element must contain no Text nodes (other than inter-element whitespace) and no element nodes.

Most HTML elements whose content model is "nothing" are also, for convenience, void elements (elements that have no end tag in the HTML syntax). However, these are entirely separate concepts.

3.2.4.2 Kinds of content

Each element in HTML falls into zero or more categories that group elements with similar characteristics together. The following broad categories are used in this specification:

• Metadata content
• Flow content
• Sectioning content
• Heading content
• Phrasing content
• Embedded content
• Interactive content

Some elements also fall into other categories, which are defined in other parts of this specification.

These categories are related as follows:

Sectioning content, heading content, phrasing content, embedded content, and interactive content are all types of flow content. Metadata is sometimes flow content. Metadata and interactive content are sometimes phrasing content. Embedded content is also a type of phrasing content, and sometimes is interactive content.

Other categories are also used for specific purposes, e.g. form controls are specified using a number of categories to define common requirements. Some elements have unique requirements and do not fit into any particular category.

3.2.4.2.1 Metadata content

Metadata content is content that sets up the presentation or behavior of the rest of the content, or that sets up the relationship of the document with other documents, or that conveys other "out of band" information.

• base
• link
• meta
• noscript
• script
• style
• template
• title

Elements from other namespaces whose semantics are primarily metadata-related (e.g. RDF) are also metadata content.

<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:r="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xml:lang="en">
 <head>
  <title>Hedral's Home Page</title>
  <r:RDF>
   <Person xmlns="http://www.w3.org/2000/10/swap/pim/contact#"
           r:about="https://hedral.example.com/#">
    <fullName>Cat Hedral</fullName>
    <mailbox r:resource="mailto:hedral@damowmow.com"/>
    <personalTitle>Sir</personalTitle>
   </Person>
  </r:RDF>
 </head>
 <body>
  <h1>My home page</h1>
  <p>I like playing with string, I guess. Sister says squirrels are fun
  too so sometimes I follow her to play with them.</p>
 </body>
</html>

3.2.4.2.2 Flow content

Most elements that are used in the body of documents and applications are categorized as flow content.

• a
• abbr
• address
• area (if it is a descendant of a map element)
• article
• aside
• audio
• b
• bdi
• bdo
• blockquote
• br
• button
• canvas
• cite
• code
• data
• datalist
• del
• details
• dfn
• dialog
• div
• dl
• em
• embed
• fieldset
• figure
• footer
• form
• h1
• h2
• h3
• h4
• h5
• h6
• header
• hgroup
• hr
• i
• iframe
• img
• input
• ins
• kbd
• label
• link (if it is allowed in the body)
• main (if it is a hierarchically correct main element)
• map
• mark
• MathML math
• menu
• meta (if the itemprop attribute is present)
• meter
• nav
• noscript
• object
• ol
• output
• p
• picture
• pre
• progress
• q
• ruby
• s
• samp
• script
• search
• section
• select
• slot
• small
• span
• strong
• sub
• sup
• SVG svg
• table
• template
• textarea
• time
• u
• ul
• var
• video
• wbr
• autonomous custom elements
• text

3.2.4.2.3 Sectioning content

Sectioning content is content that defines the scope of header and footer elements.

• article
• aside
• nav
• section

3.2.4.2.4 Heading content

Heading content defines the heading of a section (whether explicitly marked up using sectioning content elements, or implied by the heading content itself).

• h1
• h2
• h3
• h4
• h5
• h6
• hgroup (if it has a descendant h1 to h6 element)

3.2.4.2.5 Phrasing content

Phrasing content is the text of the document, as well as elements that mark up that text at the intra-paragraph level. Runs of phrasing content form paragraphs.

• a
• abbr
• area (if it is a descendant of a map element)
• audio
• b
• bdi
• bdo
• br
• button
• canvas
• cite
• code
• data
• datalist
• del
• dfn
• em
• embed
• i
• iframe
• img
• input
• ins
• kbd
• label
• link (if it is allowed in the body)
• map
• mark
• MathML math
• meta (if the itemprop attribute is present)
• meter
• noscript
• object
• output
• picture
• progress
• q
• ruby
• s
• samp
• script
• select
• slot
• small
• span
• strong
• sub
• sup
• SVG svg
• template
• textarea
• time
• u
• var
• video
• wbr
• autonomous custom elements
• text

Most elements that are categorized as phrasing content can only contain elements that are themselves categorized as phrasing content, not any flow content.

Text, in the context of content models, means either nothing, or Text nodes. Text is sometimes used as a content model on its own, but is also phrasing content, and can be inter-element whitespace (if the Text nodes are empty or contain just ASCII whitespace).

Text nodes and attribute values must consist of scalar values, excluding noncharacters, and controls other than ASCII whitespace. This specification includes extra constraints on the exact value of Text nodes and attribute values depending on their precise context.

3.2.4.2.6 Embedded content

Embedded content is content that imports another resource into the document, or content from another vocabulary that is inserted into the document.

• audio
• canvas
• embed
• iframe
• img
• MathML math
• object
• picture
• SVG svg
• video

Elements that are from namespaces other than the HTML namespace and that convey content but not metadata, are embedded content for the purposes of the content models defined in this specification. (For example, MathML or SVG.)

Some embedded content elements can have fallback content: content that is to be used when the external resource cannot be used (e.g. because it is of an unsupported format). The element definitions state what the fallback is, if any.

3.2.4.2.7 Interactive content

Interactive content is content that is specifically intended for user interaction.

• a (if the href attribute is present)
• audio (if the controls attribute is present)
• button
• details
• embed
• iframe
• img (if the usemap attribute is present)
• input (if the type attribute is not in the Hidden state)
• label
• select
• textarea
• video (if the controls attribute is present)

3.2.4.2.8 Palpable content

As a general rule, elements whose content model allows any flow content or phrasing content should have at least one node in its contents that is palpable content and that does not have the hidden attribute specified.

Palpable content makes an element non-empty by providing either some descendant non-empty text, or else something users can hear (audio elements) or view (video, img, or canvas elements) or otherwise interact with (for example, interactive form controls).

This requirement is not a hard requirement, however, as there are many cases where an element can be empty legitimately, for example when it is used as a placeholder which will later be filled in by a script, or when the element is part of a template and would on most pages be filled in but on some pages is not relevant.

Conformance checkers are encouraged to provide a mechanism for authors to find elements that fail to fulfill this requirement, as an authoring aid.

The following elements are palpable content:

• a
• abbr
• address
• article
• aside
• audio (if the controls attribute is present)
• b
• bdi
• bdo
• blockquote
• button
• canvas
• cite
• code
• data
• del
• details
• dfn
• div
• dl (if the element's children include at least one name-value group)
• em
• embed
• fieldset
• figure
• footer
• form
• h1
• h2
• h3
• h4
• h5
• h6
• header
• hgroup
• i
• iframe
• img
• input (if the type attribute is not in the Hidden state)
• ins
• kbd
• label
• main
• map
• mark
• MathML math
• menu (if the element's children include at least one li element)
• meter
• nav
• object
• ol (if the element's children include at least one li element)
• output
• p
• picture
• pre
• progress
• q
• ruby
• s
• samp
• search
• section
• select
• small
• span
• strong
• sub
• sup
• SVG svg
• table
• textarea
• time
• u
• ul (if the element's children include at least one li element)
• var
• video
• autonomous custom elements
• text that is not inter-element whitespace

3.2.4.2.9 Script-supporting elements

Script-supporting elements are those that do not represent anything themselves (i.e. they are not rendered), but are used to support scripts, e.g. to provide functionality for the user.

The following elements are script-supporting elements:

• script
• template

3.2.4.3 Transparent content models

Some elements are described as transparent; they have "transparent" in the description of their content model. The content model of a transparent element is derived from the content model of its parent element: the elements required in the part of the content model that is "transparent" are the same elements as required in the part of the content model of the parent of the transparent element in which the transparent element finds itself.

In some cases, where transparent elements are nested in each other, the process has to be applied iteratively.

<p><object><param><ins><map><a href="/">Apples</a></map></ins></object></p>

When a transparent element has no parent, then the part of its content model that is "transparent" must instead be treated as accepting any flow content.

3.2.4.4 Paragraphs

The term paragraph as defined in this section is used for more than just the definition of the p element. The paragraph concept defined here is used to describe how to interpret documents. The p element is merely one of several ways of marking up a paragraph.

A paragraph is typically a run of phrasing content that forms a block of text with one or more sentences that discuss a particular topic, as in typography, but can also be used for more general thematic grouping. For instance, an address is also a paragraph, as is a part of a form, a byline, or a stanza in a poem.

<section>
  <h2>Example of paragraphs</h2>
  This is the <em>first</em> paragraph in this example.
  <p>This is the second.</p>
  <!-- This is not a paragraph. -->
</section>

Paragraphs in flow content are defined relative to what the document looks like without the a, ins, del, and map elements complicating matters, since those elements, with their hybrid content models, can straddle paragraph boundaries, as shown in the first two examples below.

Generally, having elements straddle paragraph boundaries is best avoided. Maintaining such markup can be difficult.

<section>
  <ins><h2>Example of paragraphs</h2>
  This is the <em>first</em> paragraph in</ins> this example<del>.
  <p>This is the second.</p></del>
  <!-- This is not a paragraph. -->
</section>

A paragraph is also formed explicitly by p elements.

The p element can be used to wrap individual paragraphs when there would otherwise not be any content other than phrasing content to separate the paragraphs from each other.

<header>
 Welcome!
 <a href="about.html">
  This is home of...
  <h1>The Falcons!</h1>
  The Lockheed Martin multirole jet fighter aircraft!
 </a>
 This page discusses the F-16 Fighting Falcon's innermost secrets.
</header>

<header>
 <p>Welcome! <a href="about.html">This is home of...</a></p>
 <h1><a href="about.html">The Falcons!</a></h1>
 <p><a href="about.html">The Lockheed Martin multirole jet
 fighter aircraft!</a> This page discusses the F-16 Fighting
 Falcon's innermost secrets.</p>
</header>

<section>
 <h2>My Cats</h2>
 You can play with my cat simulator.
 <object data="cats.sim">
  To see the cat simulator, use one of the following links:
  <ul>
   <li><a href="cats.sim">Download simulator file</a>
   <li><a href="https://sims.example.com/watch?v=LYds5xY4INU">Use online simulator</a>
  </ul>
  Alternatively, upgrade to the Mellblom Browser.
 </object>
 I'm quite proud of it.
</section>

<section>
 <h2>My Cats</h2>
 <p>You can play with my cat simulator.</p>
 <object data="cats.sim">
  <p>To see the cat simulator, use one of the following links:</p>
  <ul>
   <li><a href="cats.sim">Download simulator file</a>
   <li><a href="https://sims.example.com/watch?v=LYds5xY4INU">Use online simulator</a>
  </ul>
  <p>Alternatively, upgrade to the Mellblom Browser.</p>
 </object>
 <p>I'm quite proud of it.</p>
</section>

3.2.5 Global attributes

The following attributes are common to and may be specified on all HTML elements:

• accesskey
• autocapitalize
• autocorrect
• autofocus
• contenteditable
• dir
• draggable
• enterkeyhint
• hidden
• inert
• inputmode
• is
• itemid
• itemprop
• itemref
• itemscope
• itemtype
• lang
• nonce
• popover
• spellcheck
• style
• tabindex
• title
• translate
• writingsuggestions

DOM defines the user agent requirements for the class, id, and slot attributes for any element in any namespace. [DOM]

The class, id, and slot attributes may be specified on all HTML elements.

When specified on HTML elements, the class attribute must have a value that is a set of space-separated tokens representing the various classes that the element belongs to.

When specified on HTML elements, the id attribute value must be unique amongst all the IDs in the element's tree and must contain at least one character. The value must not contain any ASCII whitespace.

There are no conformance requirements for the slot attribute specific to HTML elements.

The slot attribute is used to assign a slot to an element: an element with a slot attribute is assigned to the slot created by the slot element whose name attribute's value matches that slot attribute's value — but only if that slot element finds itself in the shadow tree whose root's host has the corresponding slot attribute value.

To enable assistive technology products to expose a more fine-grained interface than is otherwise possible with HTML elements and attributes, a set of annotations for assistive technology products can be specified (the ARIA role and aria-* attributes). [ARIA]

The following event handler content attributes may be specified on any HTML element:

• onauxclick
• onbeforeinput
• onbeforematch
• onbeforetoggle
• onblur*
• oncancel
• oncanplay
• oncanplaythrough
• onchange
• onclick
• onclose
• oncontextlost
• oncontextmenu
• oncontextrestored
• oncopy
• oncuechange
• oncut
• ondblclick
• ondrag
• ondragend
• ondragenter
• ondragleave
• ondragover
• ondragstart
• ondrop
• ondurationchange
• onemptied
• onended
• onerror*
• onfocus*
• onformdata
• oninput
• oninvalid
• onkeydown
• onkeypress
• onkeyup
• onload*
• onloadeddata
• onloadedmetadata
• onloadstart
• onmousedown
• onmouseenter
• onmouseleave
• onmousemove
• onmouseout
• onmouseover
• onmouseup
• onpaste
• onpause
• onplay
• onplaying
• onprogress
• onratechange
• onreset
• onresize*
• onscroll*
• onscrollend*
• onsecuritypolicyviolation
• onseeked
• onseeking
• onselect
• onslotchange
• onstalled
• onsubmit
• onsuspend
• ontimeupdate
• ontoggle
• onvolumechange
• onwaiting
• onwheel

The attributes marked with an asterisk have a different meaning when specified on body elements as those elements expose event handlers of the Window object with the same names.

While these attributes apply to all elements, they are not useful on all elements. For example, only media elements will ever receive a volumechange event fired by the user agent.

Custom data attributes (e.g. data-foldername or data-msgid) can be specified on any HTML element, to store custom data, state, annotations, and similar, specific to the page.

In HTML documents, elements in the HTML namespace may have an xmlns attribute specified, if, and only if, it has the exact value "http://www.w3.org/1999/xhtml". This does not apply to XML documents.

In HTML, the xmlns attribute has absolutely no effect. It is basically a talisman. It is allowed merely to make migration to and from XML mildly easier. When parsed by an HTML parser, the attribute ends up in no namespace, not the "http://www.w3.org/2000/xmlns/" namespace like namespace declaration attributes in XML do.

In XML, an xmlns attribute is part of the namespace declaration mechanism, and an element cannot actually have an xmlns attribute in no namespace specified.

XML also allows the use of the xml:space attribute in the XML namespace on any element in an XML document. This attribute has no effect on HTML elements, as the default behavior in HTML is to preserve whitespace. [XML]

There is no way to serialize the xml:space attribute on HTML elements in the text/html syntax.

3.2.5.1 The title attribute

The title attribute represents advisory information for the element, such as would be appropriate for a tooltip. On a link, this could be the title or a description of the target resource; on an image, it could be the image credit or a description of the image; on a paragraph, it could be a footnote or commentary on the text; on a citation, it could be further information about the source; on interactive content, it could be a label for, or instructions for, use of the element; and so forth. The value is text.

Relying on the title attribute is currently discouraged as many user agents do not expose the attribute in an accessible manner as required by this specification (e.g., requiring a pointing device such as a mouse to cause a tooltip to appear, which excludes keyboard-only users and touch-only users, such as anyone with a modern phone or tablet).

If this attribute is omitted from an element, then it implies that the title attribute of the nearest ancestor HTML element with a title attribute set is also relevant to this element. Setting the attribute overrides this, explicitly stating that the advisory information of any ancestors is not relevant to this element. Setting the attribute to the empty string indicates that the element has no advisory information.

If the title attribute's value contains U+000A LINE FEED (LF) characters, the content is split into multiple lines. Each U+000A LINE FEED (LF) character represents a line break.

<p>My logs show that there was some interest in <abbr title="Hypertext
Transport Protocol">HTTP</abbr> today.</p>

Some elements, such as link, abbr, and input, define additional semantics for the title attribute beyond the semantics described above.

3.2.5.2 The lang and xml:lang attributes

The lang attribute (in no namespace) specifies the primary language for the element's contents and for any of the element's attributes that contain text. Its value must be a valid BCP 47 language tag, or the empty string. Setting the attribute to the empty string indicates that the primary language is unknown. [BCP47]

The lang attribute in the XML namespace is defined in XML. [XML]

If these attributes are omitted from an element, then the language of this element is the same as the language of its parent element, if any (except for slot elements in a shadow tree).

The lang attribute in no namespace may be used on any HTML element.

The lang attribute in the XML namespace may be used on HTML elements in XML documents, as well as elements in other namespaces if the relevant specifications allow it (in particular, MathML and SVG allow lang attributes in the XML namespace to be specified on their elements). If both the lang attribute in no namespace and the lang attribute in the XML namespace are specified on the same element, they must have exactly the same value when compared in an ASCII case-insensitive manner.

Authors must not use the lang attribute in the XML namespace on HTML elements in HTML documents. To ease migration to and from XML, authors may specify an attribute in no namespace with no prefix and with the literal localname "xml:lang" on HTML elements in HTML documents, but such attributes must only be specified if a lang attribute in no namespace is also specified, and both attributes must have the same value when compared in an ASCII case-insensitive manner.

The attribute in no namespace with no prefix and with the literal localname "xml:lang" has no effect on language processing.

3.2.5.3 The translate attribute

The translate attribute is used to specify whether an element's attribute values and the values of its Text node children are to be translated when the page is localized, or whether to leave them unchanged. It is an attribute is an enumerated attribute with the following keywords and states:

The attribute's missing value default and invalid value default are both the inherit state.

Each element (even non-HTML elements) has a translation mode, which is in either the translate-enabled state or the no-translate state. If an HTML element's translate attribute is in the yes state, then the element's translation mode is in the translate-enabled state; otherwise, if the element's translate attribute is in the no state, then the element's translation mode is in the no-translate state. Otherwise, either the element's translate attribute is in the inherit state, or the element is not an HTML element and thus does not have a translate attribute; in either case, the element's translation mode is in the same state as its parent element's, if any, or in the translate-enabled state, if the element's parent element is null.

When an element is in the translate-enabled state, the element's translatable attributes and the values of its Text node children are to be translated when the page is localized.

When an element is in the no-translate state, the element's attribute values and the values of its Text node children are to be left as-is when the page is localized, e.g. because the element contains a person's name or a name of a computer program.

The following attributes are translatable attributes:

• abbr on th elements
• alt on area, img, and input elements
• content on meta elements, if the name attribute specifies a metadata name whose value is known to be translatable
• download on a and area elements
• label on optgroup, option, and track elements
• lang on HTML elements; must be "translated" to match the language used in the translation
• placeholder on input and textarea elements
• srcdoc on iframe elements; must be parsed and recursively processed
• style on HTML elements; must be parsed and recursively processed (e.g. for the values of 'content' properties)
• title on all HTML elements
• value on input elements with a type attribute in the Button state or the Reset Button state

Other specifications may define other attributes that are also translatable attributes. For example, ARIA would define the aria-label attribute as translatable.

<!DOCTYPE HTML>
<html lang=en> <!-- default on the document element is translate=yes -->
 <head>
  <title>The Bee Game</title> <!-- implied translate=yes inherited from ancestors -->
 </head>
 <body>
  <p>The Bee Game is a text adventure game in English.</p>
  <p>When the game launches, the first thing you should do is type
  <kbd translate=no>eat honey</kbd>. The game will respond with:</p>
  <pre><samp translate=no>Yum yum! That was some good honey!</samp></pre>
 </body>
</html>

3.2.5.4 The dir attribute

The dir attribute is an enumerated attribute with the following keywords and states:

The attribute's missing value default and invalid value default are both the undefined state.

The directionality of an element (any element, not just an HTML element) is either 'ltr' or 'rtl'. To compute the directionality given an element element, switch on element's dir attribute state:

ltr

Return 'ltr'.

rtl

Return 'rtl'.

auto

1. Let result be the auto directionality of element.

2. If result is null, then return 'ltr'.

3. Return result.

undefined

If element is a bdi element

1. Let result be the auto directionality of element.

2. If result is null, then return 'ltr'.

3. Return result.

If element is an input element whose type attribute is in the Telephone state

Return 'ltr'.

Otherwise

Return the parent directionality of element.

Since the dir attribute is only defined for HTML elements, it cannot be present on elements from other namespaces. Thus, elements from other namespaces always end up using the parent directionality.

The auto-directionality form-associated elements are:

• input elements whose type attribute is in the Hidden, Text, Search, Telephone, URL, Email, Password, Submit Button, Reset Button, or Button state, and

• textarea elements.

To compute the auto directionality given an element element:

1. If element is an auto-directionality form-associated element:

   1. If element's value contains a character of bidirectional character type AL or R, and there is no character of bidirectional character type L anywhere before it in the element's value, then return 'rtl'. [BIDI]

   2. If element's value is not the empty string, then return 'ltr'.

   3. Return null.

2. If element is a slot element whose root is a shadow root and element's assigned nodes are not empty:

   1. For each node child of element's assigned nodes:

      1. Let childDirection be null.

      2. If child is a Text node, then set childDirection to the text node directionality of child.

      3. Otherwise:

         1. Assert: child is an Element node.

         2. Set childDirection to the contained text auto directionality of child with canExcludeRoot set to true.

      4. If childDirection is not null, then return childDirection.

   2. Return null.

3. Return the contained text auto directionality of element with canExcludeRoot set to false.

To compute the contained text auto directionality of an element element with a boolean canExcludeRoot:

1. For each node descendant of element's descendants, in tree order:

   1. If any of

      • descendant
      • any ancestor element of descendant that is a descendant of element
      • if canExcludeRoot is true, element

      is one of

      • a bdi element
      • a script element
      • a style element
      • a textarea element
      • an element whose dir attribute is not in the undefined state

      then continue.

   2. If descendant is a slot element whose root is a shadow root, then return the directionality of that shadow root's host.

   3. If descendant is not a Text node, then continue.

   4. Let result be the text node directionality of descendant.

   5. If result is not null, then return result.

2. Return null.

To compute the text node directionality given a Text node text:

1. If text's data does not contain a code point whose bidirectional character type is L, AL, or R, then return null. [BIDI]

2. Let codePoint be the first code point in text's data whose bidirectional character type is L, AL, or R.

3. If codePoint is of bidirectional character type AL or R, then return 'rtl'.

4. If codePoint is of bidirectional character type L, then return 'ltr'.

To compute the parent directionality given an element element:

1. Let parentNode be element's parent node.

2. If parentNode is a shadow root, then return the directionality of parentNode's host.

3. If parentNode is an element, then return the directionality of parentNode.

4. Return 'ltr'.

The directionality of an attribute of an HTML element, which is used when the text of that attribute is to be included in the rendering in some manner, is determined as per the first appropriate set of steps from the following list:

If the attribute is a directionality-capable attribute and the element's dir attribute is in the auto state

Find the first character (in logical order) of the attribute's value that is of bidirectional character type L, AL, or R. [BIDI]

If such a character is found and it is of bidirectional character type AL or R, the directionality of the attribute is 'rtl'.

Otherwise, the directionality of the attribute is 'ltr'.

Otherwise

The directionality of the attribute is the same as the element's directionality.

The following attributes are directionality-capable attributes:

• abbr on th elements
• alt on area, img, and input elements
• content on meta elements, if the name attribute specifies a metadata name whose value is primarily intended to be human-readable rather than machine-readable
• label on optgroup, option, and track elements
• placeholder on input and textarea elements
• title on all HTML elements

document.dir [ = value ]

✔MDN

HTMLElement/dir

Support in all current engines.

Firefox1+Safari3+Chrome1+

---

Opera12.1+Edge79+

---

Edge (Legacy)12+Internet Explorer5.5+

---

Firefox Android?Safari iOS1+Chrome Android?WebView Android?Samsung Internet?Opera Android12.1+

Returns the html element's dir attribute's value, if any.

Can be set, to either "ltr", "rtl", or "auto" to replace the html element's dir attribute's value.

If there is no html element, returns the empty string and ignores new values.

Authors are strongly encouraged to use the dir attribute to indicate text direction rather than using CSS, since that way their documents will continue to render correctly even in the absence of CSS (e.g. as interpreted by search engines).

<p dir=auto class="u1"><b><bdi>Student</bdi>:</b> How do you write "What's your name?" in Arabic?</p>
<p dir=auto class="u2"><b><bdi>Teacher</bdi>:</b> ما اسمك؟</p>
<p dir=auto class="u1"><b><bdi>Student</bdi>:</b> Thanks.</p>
<p dir=auto class="u2"><b><bdi>Teacher</bdi>:</b> That's written "شكرًا".</p>
<p dir=auto class="u2"><b><bdi>Teacher</bdi>:</b> Do you know how to write "Please"?</p>
<p dir=auto class="u1"><b><bdi>Student</bdi>:</b> "من فضلك", right?</p>

3.2.5.5 The style attribute

All HTML elements may have the style content attribute set. This is a style attribute as defined by CSS Style Attributes. [CSSATTR]

Documents that use style attributes on any of their elements must still be comprehensible and usable if those attributes were removed.

In particular, using the style attribute to hide and show content, or to convey meaning that is otherwise not included in the document, is non-conforming. (To hide and show content, use the hidden attribute.)

element.style

Returns a CSSStyleDeclaration object for the element's style attribute.

<p>My sweat suit is <span style="color: green; background:
transparent">green</span> and my eyes are <span style="color: blue;
background: transparent">blue</span>.</p>

3.2.5.6 Embedding custom non-visible data with the data-* attributes

A custom data attribute is an attribute in no namespace whose name starts with the string "data-", has at least one character after the hyphen, is XML-compatible, and contains no ASCII upper alphas.

All attribute names on HTML elements in HTML documents get ASCII-lowercased automatically, so the restriction on ASCII uppercase letters doesn't affect such documents.

Custom data attributes are intended to store custom data, state, annotations, and similar, private to the page or application, for which there are no more appropriate attributes or elements.

These attributes are not intended for use by software that is not known to the administrators of the site that uses the attributes. For generic extensions that are to be used by multiple independent tools, either this specification should be extended to provide the feature explicitly, or a technology like microdata should be used (with a standardized vocabulary).

<ol>
 <li data-length="2m11s">Beyond The Sea</li>
 ...
</ol>

<p>The third <span data-mytrans-de="Anspruch">claim</span> covers the case of <span
translate="no">HTML</span> markup.</p>

<script>
 if ('PaymentRequest' in window) {
   document.documentElement.dataset.hasPaymentRequest = '';
 }
</script>

Every HTML element may have any number of custom data attributes specified, with any value.

Authors should carefully design such extensions so that when the attributes are ignored and any associated CSS dropped, the page is still usable.

JavaScript libraries may use the custom data attributes, as they are considered to be part of the page on which they are used. Authors of libraries that are reused by many authors are encouraged to include their name in the attribute names, to reduce the risk of clashes. Where it makes sense, library authors are also encouraged to make the exact name used in the attribute names customizable, so that libraries whose authors unknowingly picked the same name can be used on the same page, and so that multiple versions of a particular library can be used on the same page even when those versions are not mutually compatible.

element.dataset

Returns a DOMStringMap object for the element's data-* attributes.

Hyphenated names become camel-cased. For example, data-foo-bar="" becomes element.dataset.fooBar.

The DOMStringMap interface is used for the dataset attribute. Each DOMStringMap has an associated element.

<div class="spaceship" data-ship-id="92432"
     data-weapons="laser 2" data-shields="50%"
     data-x="30" data-y="10" data-z="90">
 <button class="fire"
         onclick="spaceships[this.parentNode.dataset.shipId].fire()">
  Fire
 </button>
</div>

<img class="tower" id="tower5" data-x="12" data-y="5"
     data-ai="robotarget" data-hp="46" data-ability="flames"
     src="towers/rocket.png" alt="Rocket Tower">

function splashDamage(node, x, y, damage) {
  if (node.classList.contains('tower') && // checking the 'class' attribute
      node.dataset.x == x && // reading the 'data-x' attribute
      node.dataset.y == y) { // reading the 'data-y' attribute
    var hp = parseInt(node.dataset.hp); // reading the 'data-hp' attribute
    hp = hp - damage;
    if (hp < 0) {
      hp = 0;
      node.dataset.ai = 'dead'; // setting the 'data-ai' attribute
      delete node.dataset.ability; // removing the 'data-ability' attribute
    }
    node.dataset.hp = hp; // setting the 'data-hp' attribute
  }
}

3.2.6 The innerText and outerText properties

element.innerText [ = value ]

Returns the element's text content "as rendered".

Can be set, to replace the element's children with the given value, but with line breaks converted to br elements.

element.outerText [ = value ]

✔MDN

HTMLElement/outerText

Support in all current engines.

Firefox98+Safari1.3+Chrome1+

---

Opera12.1+Edge79+

---

Edge (Legacy)12+Internet Explorer5.5+

---

Firefox Android?Safari iOS?Chrome Android?WebView Android1+Samsung Internet?Opera Android12.1+

Returns the element's text content "as rendered".

Can be set, to replace the element with the given value, but with line breaks converted to br elements.

3.2.7 Requirements relating to the bidirectional algorithm

Text content in HTML elements with Text nodes in their contents, and text in attributes of HTML elements that allow free-form text, may contain characters in the ranges U+202A to U+202E and U+2066 to U+2069 (the bidirectional-algorithm formatting characters). [BIDI]

Authors are encouraged to use the dir attribute, the bdo element, and the bdi element, rather than maintaining the bidirectional-algorithm formatting characters manually. The bidirectional-algorithm formatting characters interact poorly with CSS.