HTML 5.1: 4.3. Sections

4.3. Sections

4.3.1. The `body`#elementdef-bodyReferenced in:1.9. A quick introduction to HTML (2) (3) (4) (5) (6) (7)3.1. Documents3.1.3. DOM tree accessors (2) (3) (4) (5) (6) (7) (8) (9) (10) (11)3.2.5. Global attributes4.1.1. The html element4.3.1. The body element (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16)4.3.9. The address element (2) (3) (4) (5)4.3.10. Headings and sections4.3.10.1. Creating an outline4.3.10.2. Sample outlines (2)4.3.11. Usage summary4.7.6. The iframe element (2)5.2. Inert subtrees (2)5.4.4. Processing model5.4.6. Focus management APIs6.6.6. Page load processing model for media (2)6.6.7. Page load processing model for content that uses plugins (2)7.1.5.1. Event handlers7.1.5.2. Event handlers on elements, Document objects, and Window objects8.1. Writing HTML documents8.1.2.4. Optional tags (2) (3) (4) (5) (6) (7) (8)8.2.3.1. The insertion mode8.2.3.2. The stack of open elements8.2.5.4.7. The "in body" insertion mode (2) (3) (4) (5)8.2.8.1. Misnested tags: (2) (3) (4)8.2.8.2. Misnested tags: (2) (3) (4) (5) (6) (7)8.2.8.3. Unexpected markup in tables (2) (3) (4) (5) (6) (7) (8) (9) (10) (11)8.2.8.4. Scripts that modify the page as it is being parsed (2) (3)8.2.8.6. Unclosed formatting elements10.3.2. The page (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22)10.3.10. Margin collapsing quirks (2)11.2. Non-conforming features (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)11.3.4. Other elements, attributes and APIs (2) (3) (4) (5) (6) (7) (8)Elements (2)Element content categoriesAttributes (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13)Element Interfaces element

Categories:

Sectioning root.

Contexts in which this element can be used:

As the second element in an html element.

Content model:

Flow content.

Tag omission in text/html:

A body element’s start tag may be omitted if the element is empty, or if the first thing inside the body element is not a space character or a comment, except if the first thing inside the body element is a meta, link, script, style, or template element.

A body element’s end tag may be omitted if the body element is not immediately followed by a comment.

Content attributes:

Global attributes

onafterprint

onbeforeprint

onbeforeunload

onhashchange

onlanguagechange

onmessage

onoffline

ononline

onpagehide

onpageshow

onpopstate

onrejectionhandled

onstorage

onunhandledrejection

onunload

Allowed ARIA role attribute values:

document role (default - do not set), application.

Allowed ARIA state and property attributes:

Global aria-* attributes

Any aria-* attributes applicable to the allowed roles.

DOM interface:

interface HTMLBodyElement#htmlbodyelement-htmlbodyelementReferenced in:4.3.1. The body element11.3.4. Other elements, attributes and APIsElementsElement Interfaces : HTMLElement {
};
HTMLBodyElement implements WindowEventHandlers;

The body element represents the content of the document.

In conforming documents, there is only one body element. The document.body IDL attribute provides scripts with easy access to a document’s body element.

Some DOM operations (for example, parts of the drag and drop model) are defined in terms of "the body element". This refers to a particular element in the DOM, as per the definition of the term, and not any arbitrary body element.

The body element exposes as event handler content attributes a number of the event handlers of the Window object. It also mirrors their event handler IDL attributes.

The onblur, onerror, onfocus, onload, onresize, and onscroll event handlers of the Window object, exposed on the body element, replace the generic event handlers with the same names normally supported by html elements.

Thus, for example, a bubbling error event dispatched on a child of the body element of a Document would first trigger the onerror event handler content attributes of that element, then that of the root html element, and only then would it trigger the onerror event handler content attribute on the body element. This is because the event would bubble from the target, to the body, to the html, to the Document, to the Window, and the event handler on the body is watching the Window not the body. A regular event listener attached to the body using addEventListener(), however, would be run when the event bubbled through the body and not when it reaches the Window object.

This page updates an indicator to show whether or not the user is online:

<!DOCTYPE HTML>
<html>
  <head>
    <title>Online or offline?</title>
    <script>
      function update(online) {
        document.getElementById('status').textContent =
        online ? 'Online' : 'Offline';
      }
    </script>
  </head>
  <body ononline="update(true)"
    onoffline="update(false)"
    onload="update(navigator.onLine)">
    <p>You are: <span id="status">(Unknown)</span></p>
  </body>
</html>

4.3.2. The `article`#elementdef-articleReferenced in:3.2.4.2.2. Flow content3.2.4.2.3. Sectioning content3.2.4.2.8. Palpable content4.3.2. The article element (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14)4.3.3. The section element (2)4.3.9. The address element (2) (3) (4)4.3.10.2. Sample outlines (2)4.3.11. Usage summary4.3.11.1. Article or section? (2) (3) (4)4.4.1. The p element4.4.4. The blockquote element4.4.11. The figure element4.4.13. The main element4.4.14. The div element4.8.6.2. Link type "author"4.8.6.3. Link type "bookmark" (2)4.8.6.12. Link type "tag"8.1.2.4. Optional tags8.2.3.2. The stack of open elementsElements (2)Element content categories (2) (3)Element Interfaces element

Categories:: Flow content, but with no main element descendants.; Sectioning content.; Palpable content.
Contexts in which this element can be used:: Where flow content is expected.
Content model:: Flow content.
Tag omission in text/html:: Neither tag is omissible
Content attributes:: Global attributes
Allowed ARIA role attribute values:: article (default - do not set), application, document or main.
Allowed ARIA state and property attributes:: Global aria-* attributes; Any aria-* attributes applicable to the allowed roles.
DOM interface:: Uses HTMLElement.

The article element represents a complete, or self-contained, composition in a document, page, application, or site and that is, in principle, independently distributable or reusable, e.g., in syndication. This could be a forum post, a magazine or newspaper article, a blog entry, a user-submitted comment, an interactive widget or gadget, or any other independent item of content. Each article should be identified, typically by including a heading (h1-h6 element) as a child of the article element.

A general rule is that the article element is appropriate only if the element’s contents would be listed explicitly in the document’s outline.

When article elements are nested, the inner article elements represent articles that are in principle related to the contents of the outer article. For instance, a blog entry on a site that accepts user-submitted comments could represent the comments as article elements nested within the article element for the blog entry.

Author information associated with an article element (q.v. the address element) does not apply to nested article elements.

When used specifically with content to be redistributed in syndication, the article element is similar in purpose to the entry element in Atom. [RFC4287]

The schema.org microdata vocabulary can be used to provide the publication date for an article element, using one of the CreativeWork subtypes.

When the main content of the page (i.e., excluding footers, headers, navigation blocks, and sidebars) is all one single self-contained composition, that content may be marked with an article, but it is technically redundant in that case (since it’s self-evident that the page is a single composition, as it is a single document).

This example shows a blog post using the article element, with some schema.org annotations:

<article typeof="schema:BlogPosting">
  <header>
    <h2 property="schema:headline">The Very First Rule of Life</h2>
    <p><time property="schema:datePublished" datetime="2009-10-09">3 days ago</time></p>
    <link property="schema:url" href="?comments=0">
  </header>
  <p>If there’s a microphone anywhere near you, assume it’s hot and
  sending whatever you’re saying to the world. Seriously.</p>
  <p>...</p>
  <footer>
    <a property="schema:discussionUrl" href="?comments=1">Show comments...</a>
  </footer>
</article>

Here is that same blog post, but showing some of the comments:

<article typeof="schema:BlogPosting">
  <header>
    <h2 property="schema:headline">The Very First Rule of Life</h2>
    <p><time property="schema:datePublished" datetime="2009-10-09">3 days ago</time></p>
    <link property="schema:url" href="?comments=0">
  </header>
  <p>If there’s a microphone anywhere near you, assume it’s hot and
  sending whatever you’re saying to the world. Seriously.</p>
  <p>...</p>
  <section>
    <h2>Comments</h2>
    <article property="schema:comment" typeof="schema:UserComments" id="c1">
      <link property="schema:url" href="#c1">
      <footer>
        <p>Posted by: <span property="schema:creator" typeof="schema:Person">
        <span property="schema:name">George Washington</span>
        </span></p>
        <p><time property="schema:commentTime" datetime="2009-10-10">15 minutes ago</time></p>
      </footer>
      <p>Yeah! Especially when talking about your lobbyist friends!</p>
    </article>
    <article property="schema:comment" typeof="schema:UserComments" id="c2">
      <link property="schema:url" href="#c2">
      <footer>
        <p>Posted by: <span property="schema:creator" typeof="schema:Person">
        <span property="schema:name">George Hammond</span>
        </span></p>
        <p><time property="schema:commentTime" datetime="2009-10-10">5 minutes ago</time></p>
      </footer>
      <p>Hey, you have the same first name as me.</p>
    </article>
  </section>
</article>

Notice the use of footer to give the information for each comment (such as who wrote it and when): the footer element can appear at the start of its section when appropriate, such as in this case. (Using header in this case wouldn’t be wrong either; it’s mostly a matter of authoring preference.)

4.3.3. The `section`#elementdef-sectionReferenced in:1.10.3. Restrictions on content models and on attribute values 3.2.4.2.2. Flow content3.2.4.2.3. Sectioning content3.2.4.2.8. Palpable content4.3.3. The section element (2) (3) (4) (5)4.3.10.1. Creating an outline4.3.10.2. Sample outlines (2)4.3.11. Usage summary4.3.11.1. Article or section? (2)4.4.1. The p element4.4.2. The hr element4.4.14. The div element4.5.8. The dfn element8.1.2.4. Optional tags8.2.3.2. The stack of open elementsElementsElement content categories (2) (3)Element Interfaces element

Categories:: Flow content.; Sectioning content.; Palpable content.
Contexts in which this element can be used:: Where flow content is expected.
Content model:: Flow content.
Tag omission in text/html:: Neither tag is omissible
Content attributes:: Global attributes
Allowed ARIA role attribute values:: region role (default - do not set), alert, alertdialog, application, contentinfo, dialog, document, log, main, marquee, presentation, search or status.
Allowed ARIA state and property attributes:: Global aria-* attributes; Any aria-* attributes applicable to the allowed roles.
DOM interface:: Uses HTMLElement.

The section element represents a generic section of a document or application. A section, in this context, is a thematic grouping of content. Each section should be identified, typically by including a heading (h1-h6 element) as a child of the section element.

Examples of sections would be chapters, the various tabbed pages in a tabbed dialog box, or the numbered sections of a thesis. A Web site’s home page could be split into sections for an introduction, news items, and contact information.

Authors are encouraged to use the article element instead of the section element when it would make sense to syndicate the contents of the element.

The section element is not a generic container element. When an element is needed only for styling purposes or as a convenience for scripting, authors are encouraged to use the div element instead. A general rule is that the section element is appropriate only if the element’s contents would be listed explicitly in the document’s outline.

In the following example, we see an article (part of a larger Web page) about apples, containing two short sections.

<article>
  <header>
    <h2>Apples</h2>
    <p>Tasty, delicious fruit!</p>
  </header>
  <p>The apple is the pomaceous fruit of the apple tree.</p>
  <section>
    <h3>Red Delicious</h3>
    <p>These bright red apples are the most common found in many
    supermarkets.</p>
  </section>
  <section>
    <h3>Granny Smith</h3>
    <p>These juicy, green apples make a great filling for
    apple pies.</p>
  </section>
</article>

Here is a graduation program with two sections, one for the list of people graduating, and one for the description of the ceremony. (The markup in this example features an uncommon style sometimes used to minimize the amount of inter-element whitespace.)

<!DOCTYPE Html>
<html
  ><head
    ><title
      >Graduation Ceremony Summer 2022</title
    ></head
  ><body
    ><h1
      >Graduation</h1
    ><section
      ><h2
        >Ceremony</h2
      ><p
        >Opening Procession</p
      ><p
        >Speech by Validactorian</p
      ><p
        >Speech by Class President</p
      ><p
        >Presentation of Diplomas</p
      ><p
        >Closing Speech by Headmaster</p
    ></section
    ><section
      ><h2
        >Graduates</h2
      ><ul
        ><li
          >Molly Carpenter</li
        ><li
          >Anastasia Luccio</li
        ><li
          >Ebenezar McCoy</li
        ><li
          >Karrin Murphy</li
        ><li
          >Thomas Raith</li
        ><li
          >Susan Rodriguez</li
      ></ul
    ></section
  ></body
></html>

In this example, a book author has marked up some sections as chapters and some as appendices, and uses CSS to style the headers in these two classes of section differently. The whole book is wrapped in an article element as part of an even larger document containing other books.

<style>
  section { border: double medium; margin: 2em; }
  section.chapter h1 { font: 2em Roboto, Helvetica Neue, sans-serif; }
  section.appendix h1 { font: small-caps 2em Roboto, Helvetica Neue, sans-serif; }
</style>
...
<article class="book">
  <header>
    <h2>My Book</h2>
    <p>A sample with not much content</p>
    <p><small>Published by Dummy Publicorp Ltd.</small></p>
  </header>

  <section class="chapter">
    <h3>My First Chapter</h3>
    <p>This is the first of my chapters. It doesn’t say much.</p>
    <p>But it has two paragraphs!</p>
  </section>
  <section class="chapter">
    <h3>It Continues: The Second Chapter</h3>
    <p>Bla dee bla, dee bla dee bla. Boom.</p>
  </section>
  <section class="chapter">
    <h3>Chapter Three: A Further Example</h3>
    <p>It’s not like a battle between brightness and earthtones would go
    unnoticed.</p>
    <p>But it might ruin my story.</p>
  </section>
  <section class="appendix">
    <h3>Appendix A: Overview of Examples</h3>
    <p>These are demonstrations.</p>
  </section>
  <section class="appendix">
    <h3>Appendix B: Some Closing Remarks</h3>
    <p>Hopefully this long example shows that you <em>can</em> style
    sections, so long as they are used to indicate actual sections.</p>
  </section>
</article>

4.3.4. The `nav`#elementdef-navReferenced in:3.2.4.2.2. Flow content3.2.4.2.3. Sectioning content3.2.4.2.8. Palpable content4.3.4. The nav element (2) (3) (4) (5) (6) (7)4.3.5. The aside element4.3.10.1. Creating an outline4.3.10.2. Sample outlines (2)4.3.11. Usage summary4.4.1. The p element4.4.13. The main element (2)4.4.14. The div element4.13.2. Bread crumb navigation8.1.2.4. Optional tags8.2.3.2. The stack of open elementsElementsElement content categories (2) (3)Element Interfaces element

Categories:: Flow content.; Sectioning content.; Palpable content.
Contexts in which this element can be used:: Where flow content is expected.
Content model:: Flow content, but with no main element descendants.
Tag omission in text/html:: Neither tag is omissible
Content attributes:: Global attributes
Allowed ARIA role attribute values:: navigation role (default - do not set) or presentation.
Allowed ARIA state and property attributes:: Global aria-* attributes; Any aria-* attributes applicable to the allowed roles.
DOM interface:: Uses HTMLElement.

The nav element represents a section of a page that links to other pages or to parts within the page: a section with navigation links.

In cases where the content of a nav element represents a list of items, use list markup to aid understanding and navigation.

Not all groups of links on a page need to be in a nav element — the element is primarily intended for sections that consist of major navigation blocks. In particular, it is common for footers to have a short list of links to various pages of a site, such as the terms of service, the home page, and a copyright page. The footer element alone is sufficient for such cases; while a nav element can be used in such cases, it is usually unnecessary.

User agents (such as screen readers) that are targeted at users who can benefit from navigation information being omitted in the initial rendering, or who can benefit from navigation information being immediately available, can use this element as a way to determine what content on the page to initially skip or provide on request (or both).

In the following example, there are two nav elements, one for primary navigation around the site, and one for secondary navigation around the page itself.

<body>
  <h1>The Wiki Center Of Exampland</h1>
  <nav>
    <ul>
      <li><a href="/">Home</a></li>
      <li><a href="/events">Current Events</a></li>
      ...more...
    </ul>
  </nav>
  <article>
    <header>
      <h2>Demos in Exampland</h2>
      <p>Written by A. N. Other.</p>
    </header>
    <nav>
      <ul>
        <li><a href="#public">Public demonstrations</a></li>
        <li><a href="#destroy">Demolitions</a></li>
        ...more...
      </ul>
    </nav>
    <div>
      <section id="public">
        <h2>Public demonstrations</h2>
        <p>...more...</p>
      </section>
      <section id="destroy">
        <h2>Demolitions</h2>
        <p>...more...</p>
      </section>
      ...more...
    </div>
    <footer>
      <p><a href="?edit">Edit</a> | <a href="?delete">Delete</a> | <a href="?Rename">Rename</a></p>
    </footer>
  </article>
  <footer>
    <p><small>© copyright 1998 Exampland Emperor</small></p>
  </footer>
</body>

In the following example, the page has several places where links are present, but only one of those places is considered a navigation section.

<body typeof="schema:Blog">
  <header>
    <h1>Wake up sheeple!</h1>
    <p><a href="news.html">News</a> -
    <a href="blog.html">Blog</a> -
    <a href="forums.html">Forums</a></p>
    <p>Last Modified: <span property="schema:dateModified">2009-04-01</span></p>
    <nav>
      <h2>Navigation</h2>
      <ul>
        <li><a href="articles.html">Index of all articles</a></li>
        <li><a href="today.html">Things sheeple need to wake up for today</a></li>
        <li><a href="successes.html">Sheeple we have managed to wake</a></li>
      </ul>
    </nav>
  </header>
  <main>
    <article property="schema:blogPosts" typeof="schema:BlogPosting">
      <header>
        <h2 property="schema:headline">My Day at the Beach</h2>
      </header>
      <main property="schema:articleBody">
        <p>Today I went to the beach and had a lot of fun.</p>
        ...more content...
      </main>
      <footer>
        <p>Posted <time property="schema:datePublished" datetime="2009-10-10">Thursday</time>.</p>
      </footer>
    </article>
    ...more blog posts...
  </main>
  <footer>
    <p>Copyright ©
      <span property="schema:copyrightYear">2010</span>
      <span property="schema:copyrightHolder">The Example Company</span>
    </p>
    <p><a href="about.html">About</a> -
      <a href="policy.html">Privacy Policy</a> -
      <a href="contact.html">Contact Us</a></p>
  </footer>
</body>

Notice the main element being used to wrap the main content of the page. In this case, all content other than the page header and footer.

You can also see microdata annotations in the above example that use the schema.org vocabulary to provide the publication date and other metadata about the blog post.

A nav element doesn’t have to contain a list, it can contain other kinds of content as well. In this navigation block, links are provided in prose:

<nav>
  <h2>Navigation</h2>
  <p>You are on my home page. To the north lies <a href="/blog">my
  blog</a>, from whence the sounds of battle can be heard. To the east
  you can see a large mountain, upon which many <a
  href="/school">school papers</a> are littered. Far up thus mountain
  you can spy a little figure who appears to be me, desperately
  scribbling a <a href="/school/thesis">thesis</a>.</p>
  <p>To the west are several exits. One fun-looking exit is labeled <a
  href="http://games.example.com/">"games"</a>. Another more
  boring-looking exit is labeled <a
  href="http://isp.example.net/">ISP™</a>.</p>
  <p>To the south lies a dark and dank <a href="/about">contacts
  page</a>. Cobwebs cover its disused entrance, and at one point you
  see a rat run quickly out of the page.</p>
</nav>

In this example, nav is used in an e-mail application, to let the user switch folders:

<p><input type=button value="Compose" onclick="compose()"></p>
<nav>
  <h2>Folders</h2>
  <ul>
    <li> <a href="/inbox" onclick="return openFolder(this.href)">Inbox</a> <span class=count></span>
    <li> <a href="/sent" onclick="return openFolder(this.href)">Sent</a>
    <li> <a href="/drafts" onclick="return openFolder(this.href)">Drafts</a>
    <li> <a href="/trash" onclick="return openFolder(this.href)">Trash</a>
    <li> <a href="/customers" onclick="return openFolder(this.href)">Customers</a>
  </ul>
</nav>

4.3.5. The `aside`#elementdef-asideReferenced in:3.2.4.2.2. Flow content3.2.4.2.3. Sectioning content3.2.4.2.8. Palpable content4.3.5. The aside element (2) (3)4.3.10.1. Creating an outline4.3.11. Usage summary4.4.1. The p element4.4.11. The figure element (2)4.4.13. The main element (2) (3) (4) (5) (6)4.6.1. The ins element4.13.5. Footnotes (2) (3)8.1.2.4. Optional tags8.2.3.2. The stack of open elementsElementsElement content categories (2) (3)Element Interfaces element

Categories:: Flow content.; Sectioning content.; Palpable content.
Contexts in which this element can be used:: Where flow content is expected.
Content model:: Flow content, but with no main element descendants.
Tag omission in text/html:: Neither tag is omissible
Content attributes:: Global attributes
Allowed ARIA role attribute values:: complementary role (default - do not set), note, search or presentation.
Allowed ARIA state and property attributes:: Global aria-* attributes; Any aria-* attributes applicable to the allowed roles.
DOM interface:: Uses HTMLElement.

The aside element represents a section of a page that consists of content that is tangentially related to the content of the parenting sectioning content, and which could be considered separate from that content. Such sections are often represented as sidebars in printed typography.

The element can be used for typographical effects like pull quotes or sidebars, for advertising, for groups of nav elements, and for other content that is considered separate from the main content of the nearest ancestor sectioning content.

It’s not appropriate to use the aside element just for parentheticals, since those are part of the main flow of the document.

The following example shows how an aside is used to mark up background material on Switzerland in a much longer news story on Europe.

<aside>
  <h2>Switzerland</h2>
  <p>Switzerland, a land-locked country in the middle of geographic
  Europe, has not joined the geopolitical European Union, though it is
  a signatory to a number of European treaties.</p>
</aside>

The following example shows how an aside is used to mark up a pull quote in a longer article.

...

<p>He later joined a large company, continuing on the same work.
<q>I love my job. People ask me what I do for fun when I’m not at
work. But I’m paid to do my hobby, so I never know what to
answer. Some people wonder what they would do if they didn’t have to
work... but I know what I would do, because I was unemployed for a
year, and I filled that time doing exactly what I do now.</q></p>

<aside>
  <q> People ask me what I do for fun when I’m not at work. But I’m
  paid to do my hobby, so I never know what to answer. </q>
</aside>

<p>Of course his work — or should that be hobby? —      isn’t his only passion. He also enjoys other pleasures.</p>

...

The following extract shows how aside can be used for blogrolls and other side content on a blog:

<body>
  <header>
    <h1>My wonderful blog</h1>
    <p>My tagline</p>
  </header>
  <aside>
    <!-- this aside contains two sections that are tangentially related
    to the page, namely, links to other blogs, and links to blog posts
    from this blog -->
    <nav>
      <h2>My blogroll</h2>
      <ul>
        <li><a href="http://blog.example.com/">Example Blog</a>
      </ul>
    </nav>
    <nav>
      <h2>Archives</h2>
      <ol reversed>
        <li><a href="/last-post">My last post</a>
        <li><a href="/first-post">My first post</a>
      </ol>
    </nav>
  </aside>
  <aside>
    <!-- this aside is tangentially related to the page also, it
    contains twitter messages from the blog author -->
    <h2>Twitter Feed</h2>
    <blockquote cite="http://twitter.example.net/t31351234">
      I’m on vacation, writing my blog.
    </blockquote>
    <blockquote cite="http://twitter.example.net/t31219752">
      I’m going to go on vacation soon.
    </blockquote>
  </aside>
  <article>
    <!-- this is a blog post -->
    <h2>My last post</h2>
    <p>This is my last post.</p>
    <footer>
      <p><a href="/last-post" rel=bookmark>Permalink</a>
    </footer>
  </article>
  <article>
    <!-- this is also a blog post -->
    <h2>My first post</h2>
    <p>This is my first post.</p>
    <aside>
      <!-- this aside is about the blog post, since it’s inside the
      <article> element; it would be wrong, for instance, to put the
        blogroll here, since the blogroll isn’t really related to this post
        specifically, only to the page as a whole -->
        <h1>Posting</h1>
        <p>While I’m thinking about it, I wanted to say something about
        posting. Posting is fun!</p>
    </aside>
    <footer>
      <p><a href="/first-post" rel=bookmark>Permalink</a>
    </footer>
  </article>
  <footer>
    <nav>
      <a href="/archives">Archives</a> —      <a href="/about">About me</a> —      <a href="/copyright">Copyright</a>
    </nav>
  </footer>
</body>

4.3.6. The `h1`#elementdef-h1Referenced in:1.9. A quick introduction to HTML (2)1.10.2. Syntax errors3.2.4.2.2. Flow content3.2.4.2.4. Heading content3.2.4.2.8. Palpable content4.3.2. The article element4.3.11. Usage summary4.4.1. The p element8.1.2.4. Optional tags8.2.3.2. The stack of open elements10.3.10. Margin collapsing quirksElementsElement content categories (2) (3)Element Interfaces, `h2`#elementdef-h2Referenced in:1.10.2. Syntax errors3.2.4.2.2. Flow content3.2.4.2.4. Heading content3.2.4.2.8. Palpable content4.4.1. The p element8.1.2.4. Optional tags8.2.3.2. The stack of open elements10.3.10. Margin collapsing quirksElementsElement content categories (2) (3)Element Interfaces, `h3`#elementdef-h3Referenced in:3.2.4.2.2. Flow content3.2.4.2.4. Heading content3.2.4.2.8. Palpable content4.4.1. The p element8.1.2.4. Optional tags8.2.3.2. The stack of open elements10.3.10. Margin collapsing quirksElementsElement content categories (2) (3)Element Interfaces, `h4`#elementdef-h4Referenced in:3.2.4.2.2. Flow content3.2.4.2.4. Heading content3.2.4.2.8. Palpable content4.4.1. The p element8.1.2.4. Optional tags8.2.3.2. The stack of open elements10.3.10. Margin collapsing quirksElementsElement content categories (2) (3)Element Interfaces, `h5`#elementdef-h5Referenced in:3.2.4.2.2. Flow content3.2.4.2.4. Heading content3.2.4.2.8. Palpable content4.4.1. The p element8.1.2.4. Optional tags8.2.3.2. The stack of open elements10.3.10. Margin collapsing quirksElementsElement content categories (2) (3)Element Interfaces, and `h6`#elementdef-h6Referenced in:3.2.4.2.2. Flow content3.2.4.2.4. Heading content3.2.4.2.8. Palpable content4.3.2. The article element4.4.1. The p element8.1.2.4. Optional tags8.2.3.2. The stack of open elements10.3.10. Margin collapsing quirksElementsElement content categories (2) (3)Element Interfaces elements

Categories:

Flow content.

Heading content.

Palpable content.

Contexts in which this element can be used:

Where flow content is expected.

Content model:

Phrasing content.

Tag omission in text/html:

Neither tag is omissible

Content attributes:

Global attributes

Allowed ARIA role attribute values:

heading role (default - do not set), tab or presentation.

Allowed ARIA state and property attributes:

Global aria-* attributes

Any aria-* attributes applicable to the allowed roles.

DOM interface:

interface HTMLHeadingElement#htmlheadingelement-htmlheadingelementReferenced in:11.3.4. Other elements, attributes and APIsElementsElement Interfaces (2) (3) (4) (5) (6) : HTMLElement {};

These elements represent headings for their sections.

The semantics and meaning of these elements are defined in the section on §4.3.10 Headings and sections.

These elements have a rank#rankReferenced in:4.3.10. Headings and sections (2) (3) (4)4.3.10.1. Creating an outline (2) (3) (4) given by the number in their name. The h1 element is said to have the highest rank, the h6 element has the lowest rank, and two elements with the same name have equal rank.

h1–h6 elements must not be used to markup subheadings, subtitles, alternative titles and taglines unless intended to be the heading for a new section or subsection. Instead use the markup patterns in the §4.13 Common idioms without dedicated elements section of the specification.

As far as their respective document outlines (their heading and section structures) are concerned, these two snippets are semantically equivalent:

<body>
  <h1>Let’s call it a draw(ing surface)</h1>
  <h2>Diving in</h2>
  <h2>Simple shapes</h2>
  <h2>Canvas coordinates</h2>
  <h3>Canvas coordinates diagram</h3>
  <h2>Paths</h2>
</body>

<body>
  <h1>Let’s call it a draw(ing surface)</h1>
  <section>
    <h2>Diving in</h2>
  </section>
  <section>
    <h2>Simple shapes</h2>
  </section>
  <section>
    <h2>Canvas coordinates</h2>
    <section>
      <h3>Canvas coordinates diagram</h3>
    </section>
  </section>
  <section>
    <h2>Paths</h2>
  </section>
</body>

Authors might prefer the former style for its terseness, or the latter style for its convenience in the face of heavy editing; which is best is purely an issue of preferred authoring style.

The two styles can be combined, for compatibility with legacy tools while still future-proofing for when that compatibility is no longer needed. This third snippet again has the same outline as the previous two:

4.3.7. The `header`#elementdef-headerReferenced in:3.2.4.2.2. Flow content3.2.4.2.8. Palpable content4.3.7. The header element (2) (3) (4) (5) (6) (7)4.3.8. The footer element4.3.9. The address element4.3.10.2. Sample outlines4.3.11. Usage summary4.4.1. The p element4.4.9. The dt element4.4.13. The main element (2) (3) (4)4.9.10. The th element4.13.1. Subheadings, subtitles, alternative titles and taglines (2) (3)8.1.2.4. Optional tags8.2.3.2. The stack of open elementsElementsElement content categories (2)Element Interfaces element

Categories:: Flow content.; Palpable content.
Contexts in which this element can be used:: Where flow content is expected.
Content model:: Flow content, but with no header, footer, or main element descendants.
Tag omission in text/html:: Neither tag is omissible
Content attributes:: Global attributes
Allowed ARIA role attribute values:: banner role (default - do not set) or presentation.
Allowed ARIA state and property attributes:: Global aria-* attributes; Any aria-* attributes applicable to the allowed roles.
DOM interface:: Uses HTMLElement.

The header element represents introductory content for its nearest ancestor sectioning content or sectioning root element. A header typically contains a group of introductory or navigational aids.

When the nearest ancestor sectioning content or sectioning root element is the body element, then it applies to the whole page.

A header element is intended to usually contain the section’s heading (an h1–h6 element), but this is not required. The header element can also be used to wrap a section’s table of contents, a search form, or any relevant logos.

Here are some sample headers. This first one is for a game:

<header>
  <p>Welcome to...</p>
  <h1>Voidwars!</h1>
</header>

The following snippet shows how the element can be used to mark up a specification’s header:

<header>
  <h1>Scalable Vector Graphics (SVG) 1.2</h1>
  <p>W3C Working Draft 27 October 2004</p>
  <dl>
    <dt>This version:</dt>
    <dd><a href="http://www.w3.org/TR/2004/WD-SVG12-20041027/">http://www.w3.org/TR/2004/WD-SVG12-20041027/</a></dd>
    <dt>Previous version:</dt>
    <dd><a href="http://www.w3.org/TR/2004/WD-SVG12-20040510/">http://www.w3.org/TR/2004/WD-SVG12-20040510/</a></dd>
    <dt>Latest version of SVG 1.2:</dt>
    <dd><a href="http://www.w3.org/TR/SVG12/">http://www.w3.org/TR/SVG12/</a></dd>
    <dt>Latest SVG Recommendation:</dt>
    <dd><a href="http://www.w3.org/TR/SVG/">http://www.w3.org/TR/SVG/</a></dd>
    <dt>Editor:</dt>
    <dd>Dean Jackson, W3C, <a href="mailto:dean@w3.org">dean@w3.org</a></dd>
    <dt>Authors:</dt>
    <dd>See <a href="#authors">Author List</a></dd>
  </dl>
  <p class="copyright"><a href="http://www.w3.org/Consortium/Legal/ipr-notic ...
</header>

The header element is not sectioning content; it doesn’t introduce a new section.

In this example, the page has a page heading given by the h1 element, and two subsections whose headings are given by h2 elements. The content after the header element is still part of the last subsection started in the header element, because the header element doesn’t take part in the outline algorithm.

<body>
  <header>
    <h1>Little Green Guys With Guns</h1>
    <nav>
      <ul>
      <li><a href="/games">Games</a>
      <li><a href="/forum">Forum</a>
      <li><a href="/download">Download</a>
      </ul>
    </nav>
    <h2>Important News</h2> <!-- this starts a second subsection -->
    <!-- this is part of the subsection entitled "Important News" -->
    <p>To play today’s games you will need to update your client.</p>
    <h2>Games</h2> <!-- this starts a third subsection -->
    </header>
    <p>You have three active games:</p>
    <!-- this is still part of the subsection entitled "Games" -->
    ...

Categories:: Flow content.; Palpable content.
Contexts in which this element can be used:: Where flow content is expected.
Content model:: Flow content, but with no header, footer, or main element descendants.
Tag omission in text/html:: Neither tag is omissible
Content attributes:: Global attributes
Allowed ARIA role attribute values:: contentinfo role (default - do not set) or presentation.
Allowed ARIA state and property attributes:: Global aria-* attributes; Any aria-* attributes applicable to the allowed roles.
DOM interface:: Uses HTMLElement.

The footer element represents a footer for its nearest ancestor sectioning content or sectioning root element. A footer typically contains information about its section such as who wrote it, links to related documents, copyright data, and the like.

When the footer element contains entire sections, they represent appendices, indexes, long colophons, verbose license agreements, and other such content.

Contact information for the author or editor of a section belongs in an address element, possibly itself inside a footer. Bylines and other information that could be suitable for both a header or a footer can be placed in either (or neither). The primary purpose of these elements is merely to help the author write self-explanatory markup that is easy to maintain and style; they are not intended to impose specific structures on authors.

Footers don’t necessarily have to appear at the end of a section, though they usually do.

When the nearest ancestor sectioning content or sectioning root element is the body element, then it applies to the whole page.

The footer element is not sectioning content; it doesn’t introduce a new section.

Here is a page with two footers, one at the top and one at the bottom, with the same content:

<body>
  <footer><a href="../">Back to index...</a></footer>
  <div>
    <h1>Lorem ipsum</h1>
    <p>The ipsum of all lorems</p>
  </div>
  <p>A dolor sit amet, consectetur adipisicing elit, sed do eiusmod
  tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim
  veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex
  ea commodo consequat. Duis aute irure dolor in reprehenderit in
  voluptate velit esse cillum dolore eu fugiat nulla
  pariatur. Excepteur sint occaecat cupidatat non proident, sunt in
  culpa qui officia deserunt mollit anim id est laborum.</p>
  <footer><a href="../">Back to index...</a></footer>
</body>

Here is an example which shows the footer element being used both for a site-wide footer and for a section footer.

<!DOCTYPE HTML>
<HTML><HEAD>
<TITLE>The Ramblings of a Scientist</TITLE>
<BODY>
<h1>The Ramblings of a Scientist</h1>
<MAIN>
  <ARTICLE>
  <H2>Episode 15</H2>
  <VIDEO SRC="/fm/015.ogv" CONTROLS PRELOAD>
  <P><A HREF="/fm/015.ogv">Download video</A>.</P>
  </VIDEO>
  <FOOTER> <!-- footer for article -->
  <P>Published <TIME DATETIME="2009-10-21T18:26-07:00">on 2009/10/21 at 6:26pm</TIME></P>
  </FOOTER>
</ARTICLE>
<ARTICLE>
  <H2>My Favorite Trains</H2>
  <P>I love my trains. My favorite train of all time is a Köf.</P>
  <P>It is fun to see them pull some coal cars because they look so
  dwarfed in comparison.</P>
  <FOOTER> <!-- footer for article -->
  <P>Published <TIME DATETIME="2009-09-15T14:54-07:00">on 2009/09/15 at 2:54pm</TIME></P>
  </FOOTER>
  </ARTICLE>
</MAIN>
<FOOTER> <!-- site wide footer -->
  <NAV>
  <P><A HREF="/credits.html">Credits</A> —      <A HREF="/tos.html">Terms of Service</A> —      <A HREF="/index.html">Blog Index</A></P>
  </NAV>
  <P>Copyright © 2009 Gordon Freeman</P>
</FOOTER>
</BODY>
</HTML>

Some site designs have what is sometimes referred to as "fat footers" — footers that contain a lot of material, including images, links to other articles, links to pages for sending feedback, special offers... in some ways, a whole "front page" in the footer.

This fragment shows the bottom of a page on a site with a "fat footer":

...
  <footer>
    <nav>
      <section>
        <h2>Articles</h2>
        <p><img src="images/somersaults.jpeg" alt=""> Go to the gym with
        our somersaults class! Our teacher Jim takes you through the paces
        in this two-part article. <a href="articles/somersaults/1">Part
        1</a> · <a href="articles/somersaults/2">Part 2</a></p>
        <p><img src="images/kindplus.jpeg"> Tired of walking on the edge of
        a clif<!-- sic -->? Our guest writer Lara shows you how to bumble
        your way through the bars. <a href="articles/kindplus/1">Read
        more...</a></p>
        <p><img src="images/crisps.jpeg"> The chips are down, now all
        that’s left is a potato. What can you do with it? <a
        href="articles/crisps/1">Read more...</a></p>
      </section>
      <ul>
        <li> <a href="/about">About us...</a>
        <li> <a href="/feedback">Send feedback!</a>
        <li> <a href="/sitemap">Sitemap</a>
      </ul>
    </nav>
    <p><small>Copyright © 2015 The Snacker —      <a href="/tos">Terms of Service</a></small></p>
  </footer>
</body>

4.3.9. The `address`#elementdef-addressReferenced in:2.2.1. Conformance classes (2)3.2.4.2.2. Flow content3.2.4.2.8. Palpable content4.3.9. The address element (2) (3) (4) (5) (6) (7)4.4.1. The p element8.1.2.4. Optional tags8.2.3.2. The stack of open elementsElementsElement content categories (2)Element Interfaces element

Categories:: Flow content.; Palpable content.
Contexts in which this element can be used:: Where flow content is expected.
Content model:: Flow content, but with no heading content descendants, no sectioning content descendants, and no header, footer, or address element descendants.
Tag omission in text/html:: Neither tag is omissible
Content attributes:: Global attributes
Allowed ARIA role attribute values:: contentinfo role.
Allowed ARIA state and property attributes:: Global aria-* attributes; Any aria-* attributes applicable to the allowed roles.
DOM interface:: Uses HTMLElement.

The address element represents the contact information for its nearest article or body element ancestor. If that is the body element, then the contact information applies to the document as a whole.

For example, a page at the W3C Web site related to HTML might include the following contact information:

<ADDRESS>
  <A href="../People/Raggett/">Dave Raggett</A>,
  <A href="../People/Arnaud/">Arnaud Le Hors</A>,
  contact persons for the <A href="Activity">W3C HTML Activity</A>
</ADDRESS>

The address element must not be used to represent arbitrary addresses (e.g., postal addresses), unless those addresses are in fact the relevant contact information. (The p element is the appropriate element for marking up postal addresses in general.)

The address element must not contain information other than contact information.

For example, the following is non-conforming use of the address element:

<ADDRESS>Last Modified: 1999/12/24 23:37:50</ADDRESS>

Typically, the address element would be included along with other information in a footer element.

The contact information for a node node is a collection of address elements defined by the first applicable entry from the following list:

If node is an article element
If node is a body element: The contact information consists of all the address elements that have node as an ancestor and do not have another body or article element ancestor that is a descendant of node.
If node has an ancestor element that is an article element
If node has an ancestor element that is a body element: The contact information of node is the same as the contact information of the nearest article or body element ancestor, whichever is nearest.
If node’s node document has a body element: The contact information of node is the same as the contact information of the body element of the Document.
Otherwise: There is no contact information for node.

User agents may expose the contact information of a node to the user, or use it for other purposes, such as indexing sections based on the sections' contact information.

In this example the footer contains contact information and a copyright notice.

<footer>
  <address>
  For more details, contact
  <a href="mailto:js@example.com">John Smith</a>.
  </address>
  <p><small>© copyright 2038 Example Corp.</small></p>
</footer>

4.3.10. Headings and sections

The h1–h6 elements are headings.

The first element of heading content in an element of sectioning content represents the heading for that section. Subsequent headings of equal or higher rank start new (implied) sections, headings of lower rank start implied subsections that are part of the previous one. In both cases, the element represents the heading of the implied section.

Certain elements are said to be sectioning roots#sectioning-rootsReferenced in:3.2.4.2.3. Sectioning content4.3.1. The body element4.3.7. The header element (2)4.3.8. The footer element (2)4.3.10. Headings and sections4.3.10.1. Creating an outline (2) (3) (4) (5) (6) (7) (8) (9)4.4.4. The blockquote element4.4.11. The figure element4.9.9. The td element4.10.16. The fieldset element4.11.1. The details element4.11.7. The dialog elementElements (2) (3) (4) (5) (6) (7)Element content categories, including blockquote and td elements. These elements can have their own outlines, but the sections and headings inside these elements do not contribute to the outlines of their ancestors.

Sectioning content elements are always considered subsections of their nearest ancestor sectioning root or their nearest ancestor element of sectioning content, whichever is nearest, regardless of what implied sections other headings may have created.

For the following fragment:

<body>
  <h1>Foo</h1>
  <h2>Bar</h2>
  <blockquote>
    <h3>Bla</h3>
  </blockquote>
  <p>Baz</p>
  <h2>Quux</h2>
  <section>
    <h3>Thud</h3>
  </section>
  <p>Grunt</p>
</body>

...the structure would be:

Foo (heading of explicit body section, containing the "Grunt" paragraph)
1. Bar (heading starting implied section, containing a block quote and the "Baz" paragraph)
2. Quux (heading starting implied section with no content other than the heading itself)
3. Thud (heading of explicit section section)

Notice how the section ends the earlier implicit section so that a later paragraph ("Grunt") is back at the top level.

Sections may contain headings of any rank, and authors are strongly encouraged to use headings of the appropriate rank for the section’s nesting level.

Authors are also encouraged to explicitly wrap sections in elements of sectioning content, instead of relying on the implicit sections generated by having multiple headings in one element of sectioning content.

For example, the following is correct:

<body>
  <h4>Apples</h4>
  <p>Apples are fruit.</p>
  <section>
    <h2>Taste</h2>
    <p>They taste lovely.</p>
    <h6>Sweet</h6>
    <p>Red apples are sweeter than green ones.</p>
    <h1>Color</h1>
    <p>Apples come in various colors.</p>
  </section>
</body>

However, the same document would be more clearly expressed as:

<body>
  <h1>Apples</h1>
  <p>Apples are fruit.</p>
  <section>
    <h2>Taste</h2>
    <p>They taste lovely.</p>
    <section>
      <h3>Sweet</h3>
      <p>Red apples are sweeter than green ones.</p>
    </section>
  </section>
  <section>
    <h2>Color</h2>
    <p>Apples come in various colors.</p>
  </section>
</body>

Both of the documents above are semantically identical and would produce the same outline in compliant user agents.

This third example is also semantically identical, and might be easier to maintain (e.g., if sections are often moved around in editing):

<body>
  <h1>Apples</h1>
  <p>Apples are fruit.</p>
  <section>
    <h1>Taste</h1>
    <p>They taste lovely.</p>
    <section>
      <h1>Sweet</h1>
      <p>Red apples are sweeter than green ones.</p>
    </section>
  </section>
  <section>
    <h1>Color</h1>
    <p>Apples come in various colors.</p>
  </section>
</body>

This final example would need explicit style rules to be rendered well in legacy browsers. Legacy browsers without CSS support would render all the headings as top-level headings.

4.3.10.1. Creating an outline

There are currently no known implementations of the outline algorithm in graphical browsers or assistive technology user agents, although the algorithm is implemented in other software such as conformance checkers. Therefore the outline algorithm cannot be relied upon to convey document structure to users. Authors are advised to use heading rank (h1-h6) to convey document structure.

This section defines an algorithm for creating an outline for a sectioning content element or a sectioning root element. It is defined in terms of a walk over the nodes of a DOM tree, in tree order, with each node being visited when it is entered and when it is exited during the walk.

The outline#outlineReferenced in:2.2.1. Conformance classes3.2.4.2.3. Sectioning content (2)4.3.3. The section element4.3.7. The header element4.3.10.1. Creating an outline (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16)4.3.10.2. Sample outlines4.4.2. The hr element4.4.13. The main element for a sectioning content element or a sectioning root element consists of a list of one or more potentially nested sections. The element for which an outline is created is said to be the outline’s owner.

A section#sectionReferenced in:4.3.10.1. Creating an outline (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) is a container that corresponds to some nodes in the original DOM tree. Each section can have one heading associated with it, and can contain any number of further nested sections. The algorithm for the outline also associates each node in the DOM tree with a particular section and potentially a heading. (The sections in the outline aren’t section elements, though some may correspond to such elements — they are merely conceptual sections.)

The following markup fragment:

<body>
  <h1>A</h1>
  <p>B</p>
  <h2>C</h2>
  <p>D</p>
  <h2>E</h2>
  <p>F</p>
</body>

...results in the following outline being created for the body node (and thus the entire document):

Section created for body node. Associated with heading "A". Also associated with paragraph "B". Nested sections:
1. Section implied for first h2 element. Associated with heading "C". Also associated with paragraph "D". No nested sections.
2. Section implied for second h2 element. Associated with heading "E". Also associated with paragraph "F". No nested sections.

The algorithm that must be followed during a walk of a DOM subtree rooted at a sectioning content element or a sectioning root element to determine that element’s outline is as follows:

Let current outline target be null. (It holds the element whose outline is being created.)
Let current section be null. (It holds a pointer to a section, so that elements in the DOM can all be associated with a section.)
Create a stack to hold elements, which is used to handle nesting. Initialize this stack to empty.
Walk over the DOM in tree order, starting with the sectioning content element or sectioning root element at the root of the subtree for which an outline is to be created, and trigger the first relevant step below for each element as the walk enters and exits it.
When exiting an element, if that element is the element at the top of the stack

The element being exited is a heading content element or an element with a hidden attribute.

Pop that element from the stack.

If the top of the stack is a heading content element or an element with a hidden attribute
Do nothing.
When entering an element with a hidden attribute
Push the element being entered onto the stack. (This causes the algorithm to skip that element and any descendants of the element.)
When entering a sectioning content element
Run these steps:
1. If current outline target is not null, run these substeps:
  1. If the current section has no heading, create an implied heading and let that be the heading for the current section.
  2. Push current outline target onto the stack.
2. Let current outline target be the element that is being entered.
3. Let current section be a newly created section for the current outline target element.
4. Associate current outline target with current section.
5. Let there be a new outline for the new current outline target, initialized with just the new current section as the only section in the outline.
When exiting a sectioning content element, if the stack is not empty
Run these steps:
1. If the current section has no heading, create an implied heading and let that be the heading for the current section.
2. Pop the top element from the stack, and let the current outline target be that element.
3. Let current section be the last section in the outline of the current outline target element.
4. Append the outline of the sectioning content element being exited to the current section. (This does not change which section is the last section in the outline.)
When entering a sectioning root element
Run these steps:
1. If current outline target is not null, push current outline target onto the stack.
2. Let current outline target be the element that is being entered.
3. Let current outline target’s parent section be current section.
4. Let current section be a newly created section for the current outline target element.
5. Let there be a new outline for the new current outline target, initialized with just the new current section as the only section in the outline.
When exiting a sectioning root element, if the stack is not empty
Run these steps:
1. If the current section has no heading, create an implied heading and let that be the heading for the current section.
2. Let current section be current outline target’s parent section.
3. Pop the top element from the stack, and let the current outline target be that element.
When exiting a sectioning content element or a sectioning root element (when the stack is empty)

The current outline target is the element being exited, and it is the sectioning content element or a sectioning root element at the root of the subtree for which an outline is being generated.

If the current section has no heading, create an implied heading and let that be the heading for the current section.

Skip to the next step in the overall set of steps. (The walk is over.)

When entering a heading content element
If the current section has no heading, let the element being entered be the heading for the current section.
Otherwise, if the element being entered has a rank equal to or higher than the heading of the last section of the outline of the current outline target, or if the heading of the last section of the outline of the current outline target is an implied heading, then create a new section and append it to the outline of the current outline target element, so that this new section is the new last section of that outline. Let current section be that new section. Let the element being entered be the new heading for the current section.

Otherwise, run these substeps:
1. Let candidate section be current section.
2. Heading loop: If the element being entered has a rank lower than the rank of the heading of the candidate section, then create a new section, and append it to candidate section. (This does not change which section is the last section in the outline.) Let current section be this new section. Let the element being entered be the new heading for the current section. Abort these substeps.
3. Let new candidate section be the section that contains candidate section in the outline of current outline target.
4. Let candidate section be new candidate section.
5. Return to the step labeled heading loop.
Push the element being entered onto the stack. (This causes the algorithm to skip any descendants of the element.)

Recall that h1 has the highest rank, and h6 has the lowest rank.
Otherwise
Do nothing.
In addition, whenever the walk exits a node, after doing the steps above, if the node is not associated with a section yet, associate the node with the section#associate-sectionReferenced in:4.8.6.3. Link type "bookmark" current section.
Associate all non-element nodes that are in the subtree for which an outline is being created with the section with which their parent element is associated.
Associate all nodes in the subtree with the heading of the section with which they are associated, if any.

The tree of sections created by the algorithm above, or a proper subset thereof, must be used when generating document outlines, for example when generating tables of contents.

The outline created for the body element of a Document is the outline of the entire document.

When creating an interactive table of contents, entries should jump the user to the relevant sectioning content element, if the section was created for a real element in the original document, or to the relevant heading content element, if the section in the tree was generated for a heading in the above process.

Selecting the first section of the document therefore always takes the user to the top of the document, regardless of where the first heading in the body is to be found.

The outline depth#outline-depthReferenced in:4.3.10.1. Creating an outline of a heading content element associated with a section section is the number of sections that are ancestors of section in the outermost outline that section finds itself in when the outlines of its Document's elements are created, plus 1. The outline depth of a heading content element not associated with a section is 1.

User agents should provide default headings for sections that do not have explicit section headings.

Consider the following snippet:

<body>
  <nav>
    <p><a href="/">Home</a></p>
  </nav>
  <p>Hello world.</p>
  <aside>
    <p>My cat is cute.</p>
  </aside>
</body>

Although it contains no headings, this snippet has three sections: a document (the body) with two subsections (a nav and an aside). A user agent could present the outline as follows:

Untitled document
1. Navigation
2. Sidebar

These default headings ("Untitled document", "Navigation", "Sidebar") are not specified by this specification, and might vary with the user’s language, the page’s language, the user’s preferences, the user agent implementor’s preferences, etc.

The following JavaScript function shows how the tree walk could be implemented. The root argument is the root of the tree to walk (either a sectioning content element or a sectioning root element), and the enter and exit arguments are callbacks that are called with the nodes as they are entered and exited. [ECMA-262]

function (root, enter, exit) {
  var node = root;
  start: while (node) {
    enter(node);
    if (node.firstChild) {
      node = node.firstChild;
      continue start;
    }
    while (node) {
      exit(node);
      if (node == root) {
        node = null;
      } else if (node.nextSibling) {
        node = node.nextSibling;
        continue start;
      } else {
        node = node.parentNode;
      }
    }
  }
}

4.3.10.2. Sample outlines

This section is non-normative.

The following document shows a straight-forward application of the outline algorithm. First, here is the document, which is a book with very short chapters and subsections:

<!DOCTYPE HTML>
<title>The Tax Book (all in one page)</title>
<h1>The Tax Book</h1>
<h2>Earning money</h2>
<p>Earning money is good.</p>
<h3>Getting a job</h3>
<p>To earn money you typically need a job.</p>
<h2>Spending money</h2>
<p>Spending is what money is mainly used for.</p>
<h3>Cheap things</h3>
<p>Buying cheap things often not cost-effective.</p>
<h3>Expensive things</h3>
<p>The most expensive thing is often not the most cost-effective either.</p>
<h2>Investing money</h2>
<p>You can lend your money to other people.</p>
<h2>Losing money</h2>
<p>If you spend money or invest money, sooner or later you will lose money.
<h3>Poor judgement</h3>
<p>Usually if you lose money it’s because you made a mistake.</p>

This book would form the following outline:

The Tax Book
1. Earning money
  1. Getting a job
2. Spending money
  1. Cheap things
  2. Expensive things
3. Investing money
4. Losing money
  1. Poor judgement

Notice that the title element does not participate in the outline.

Here is a similar document, but this time using section elements to get the same effect:

<!DOCTYPE HTML>
<title>The Tax Book (all in one page)</title>
<h1>The Tax Book</h1>
<section>
  <h1>Earning money</h1>
  <p>Earning money is good.</p>
  <section>
    <h1>Getting a job</h1>
    <p>To earn money you typically need a job.</p>
  </section>
</section>
<section>
  <h1>Spending money</h1>
  <p>Spending is what money is mainly used for.</p>
  <section>
    <h1>Cheap things</h1>
    <p>Buying cheap things often not cost-effective.</p>
  </section>
  <section>
    <h1>Expensive things</h1>
    <p>The most expensive thing is often not the most cost-effective either.</p>
  </section>
</section>
<section>
  <h1>Investing money</h1>
  <p>You can lend your money to other people.</p>
</section>
<section>
  <h1>Losing money</h1>
  <p>If you spend money or invest money, sooner or later you will lose money.
  <section>
    <h1>Poor judgement</h1>
    <p>Usually if you lose money it’s because you made a mistake.</p>
  </section>
</section>

This book would form the same outline:

The Tax Book
1. Earning money
  1. Getting a job
2. Spending money
  1. Cheap things
  2. Expensive things
3. Investing money
4. Losing money
  1. Poor judgement

A document can contain multiple top-level headings:

<!DOCTYPE HTML>
<title>Alphabetic Fruit</title>
<h1>Apples</h1>
<p>Pomaceous.</p>
<h1>Bananas</h1>
<p>Edible.</p>
<h1>Oranges</h1>
<p>Star.</p>

This would form the following simple outline consisting of three top-level sections:

Apples
Bananas
Oranges

Effectively, the body element is split into three.

Mixing both the h1–h6 model and the section/h1 model can lead to some unintuitive results.

Consider for example the following, which is just the previous example but with the contents of the (implied) body wrapped in a section:

<!DOCTYPE HTML>
<title>Alphabetic Fruit</title>
<section>
  <h1>Apples</h1>
  <p>Pomaceous.</p>
  <h1>Bananas</h1>
  <p>Edible.</p>
  <h1>Oranges</h1>
  <p>Star.</p>
</section>

The resulting outline would be:

(untitled page)
1. Apples
2. Bananas
3. Oranges

This result is described as unintuitive because it results in three subsections even though there’s only one section element. Effectively, the section is split into three, just like the implied body element in the previous example.

(In this example, "(untitled page)" is the implied heading for the body element, since it has no explicit heading.)

Headings never rise above other sections. Thus, in the following example, the first h1 does not actually describe the page header; it describes the header for the second half of the page:

<!DOCTYPE HTML>
<title>Feathers on The Site of Encyclopedic Knowledge</title>
<section>
  <h1>A plea from our caretakers</h1>
  <p>Please, we beg of you, send help! We’re stuck in the server room!</p>
</section>
<h1>Feathers</h1>
<p>Epidermal growths.</p>

The resulting outline would be:

(untitled page)
1. A plea from our caretakers
Feathers

Thus, when an article element starts with a nav block and only later has its heading, the result is that the nav block is not part of the same section as the rest of the article in the outline. For instance, take this document:

<!DOCTYPE HTML>
<title>We’re adopting a child! — Ray’s blog</title>
...

<h1>Ray’s blog</h1>

<main>
  <article>
    <header>
      <nav>
        <a href="?t=-1d">Yesterday</a>;
        <a href="?t=-7d">Last week</a>;
        <a href="?t=-1m">Last month</a>
      </nav>
    </header>
    <h2>We’re adopting a child!</h2>

    <p>As of today, Janine and I have signed the papers to become
    the proud parents of baby Diane! We’ve been looking forward to
    this day for weeks.</p>
  </article>
</main>
...

The resulting outline would be:

Ray’s blog
1. Untitled article
  1. Untitled navigation section
2. We’re adopting a child!

Also worthy of note in this example is that the header and main elements have no effect whatsoever on the document outline.

4.3.10.3. Exposing outlines to users

User agents are encouraged to expose page outlines to users to aid in navigation. This is especially true for non-visual media, e.g., screen readers.

However, to mitigate the difficulties that arise from authors misusing sectioning content, user agents are also encouraged to offer a mode that navigates the page using heading content alone.

For instance, a user agent could map the arrow keys as follows:

Shift+← Left: Go to previous section, including subsectons of previous sections
Shift+→ Right: Go to next section, including subsections of the current section
Shift+↑ Up: Go to parent section of the current section
Shift+↓ Down: Go to next section, skipping subsections of the current section

Plus in addition, the user agent could map the j and k keys to navigating to the previous or next element of heading content, regardless of the section’s outline depth and ignoring sections with no headings.

4.3.11. Usage summary

This section is non-normative.

Element	Purpose
Element	Example
`body`
`body`	<!DOCTYPE HTML> <html> <head> <title>Steve Hill’s Home Page</title> </head> <body> <p>Hard Trance is My Life.</p> </body> </html>
`article`
`article`	<article> <img src="/tumblr_masqy2s5yn1rzfqbpo1_500.jpg" alt="Yellow smiley face with the caption 'masif'"> <p>My fave Masif tee so far!</p> <footer>Posted 2 days ago</footer> </article> <article> <img src="/tumblr_m9tf6wSr6W1rzfqbpo1_500.jpg" alt=""> <p>Happy 2nd birthday Masif Saturdays!!!</p> <footer>Posted 3 weeks ago</footer> </article>
`section`
`section`	<h1>Biography</h1> <section> <h1>The facts</h1> <p>1500+ shows, 14+ countries</p> </section> <section> <h1>2010/2011 figures per year</h1> <p>100+ shows, 8+ countries</p> </section>
`nav`
`nav`	<nav> <ul> <li><a href="/">Home</a> <li><a href="/biog.html">Bio</a> <li><a href="/discog.html">Discog</a> </ul> </nav>
`aside`
`aside`	<h1>Music</h1> <p>As any burner can tell you, the event has a lot of trance.</p> <aside>You can buy the music we played at our <a href="buy.html">playlist page</a>.</aside> <p>This year we played a kind of trance that originated in Belgium, Germany, and the Netherlands in the mid 90s.</p>
`h1`–`h6`	A section heading
`h1`–`h6`	<h1>The Guide To Music On The Playa</h1> <h2>The Main Stage</h2> <p>If you want to play on a stage, you should bring one.</p> <h2>Amplified Music</h2> <p>Amplifiers up to 300W or 90dB are welcome.</p>
`header`
`header`	<article> <header> <h1>Hard Trance is My Life</h1> <p>By DJ Steve Hill and Technikal</p> </header> <p>The album with the amusing punctuation has red artwork.</p> </article>
`footer`
`footer`	<article> <h1>Hard Trance is My Life</h1> <p>The album with the amusing punctuation has red artwork.</p> <footer> <p>Artists: DJ Steve Hill and Technikal</p> </footer> </article>

4.3.11.1. Article or section?

This section is non-normative.

A section forms part of something else. An article is its own thing. But how does one know which is which? Mostly the real answer is "it depends on author intent".

For example, one could imagine a book with a "Granny Smith" chapter that just said "These juicy, green apples make a great filling for apple pies."; that would be a section because there’d be lots of other chapters on (maybe) other kinds of apples.

On the other hand, one could imagine a tweet or reddit comment or tumblr post or newspaper classified ad that just said "Granny Smith. These juicy, green apples make a great filling for apple pies."; it would then be articles because that was the whole thing.

A comment on an article is not part of the article on which it is commenting, therefore it is its own article.