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CSS

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HTML 

              
                <html data-lightMode=auto>

<body>
  <main aria-label=Content>
    <header aria-label="Content header">
      <div>
        <h1>Highlighting landmarks and headings</h1>

        <p>A bookmarklet to help with WCAG 2.1: 1.3.1 - Info and Relationships - Identifies and highlights each landmark or heading.</p>
      </div>
    </header>

    <div class=test-elements>

      <section>
        <header>header</header>
        <div role=banner>div[role=banner]</div>
        
        <aside>aside</aside>
        <div role=complementary>div[role=complementary]</div>

        <footer>footer</footer>
        <div role=contentinfo>div[role=contentinfo]</div>

        <form>form</form>
        <div role=form>div[role=form]</div>
        
        <div role=search>div[role=search]</div>
        
        <main>main</main>
        <div role=main>div[role=main]</div>
        
        <nav>nav</nav>
        <div role=navigation>div[role=navigation]</div>
        
        <section>section</section>
        <div role=region>div[role=region]</div>
      </section>

      <section>
        <h1>h1</h1>
        <div role=heading aria-level=1>div[role=heading][aria-level=1]</div>
        <h2>h2</h2>
        <div role=heading>div[role=heading]</div>
        <div role=heading aria-level=2>div[role=heading][aria-level=2]</div>
        <h3>h3</h3>
        <div role=heading aria-level=3>div[role=heading][aria-level=3]</div>
        <h4>h4</h4>
        <div role=heading aria-level=4>div[role=heading][aria-level=4]</div>
        <h5>h5</h5>
        <div role=heading aria-level=5>div[role=heading][aria-level=5]</div>
        <h6>h6</h6>
        <div role=heading aria-level=6>div[role=heading][aria-level=6]</div>

        <div role=heading aria-level=7>div[role=heading][aria-level=7]</div>
        <div role=heading aria-level=8>div[role=heading][aria-level=8]</div>
      </section>
    </div>

    <div>
      
      <h2>Bookmarklet</h2>
      
      <p>Drag this link into your bookmark bar: <a href="javascript:const outliner=(e=>{'use strict';const o={header:'#eb0000',banner:'#eb0000',aside:'#8a7500',complementary:'#8a7500',footer:'#268500',contentinfo:'#268500',form:'#062',search:'#062',main:'#0076d1',nav:'#8a7500',navigation:'#8a7500',section:'#8352ff',region:'#8352ff',h1:'#008a27','heading 1':'#008a27',h2:'#007cad','heading 2':'#007cad',h3:'#8352ff','heading 3':'#8352ff',h4:'#db009d','heading 4':'#db009d',h5:'#d63d00','heading 5':'#d63d00',h6:'#5b8000','heading 6':'#5b8000'},t=(e,o,t)=>{'static'!==getComputedStyle(e).position||e.classList.add('-js-overlay');const r=((e,o)=>{const t=document.createElement(e);return t.className=o,t})('span','-js-overlay-border');r.style.setProperty('--overlay-bg-color',t),r.style.setProperty('--overlay-color','#fff'),r.style.setProperty('--overlay-text','\''+o+'\''),e.appendChild(r)};(e=>{const r=(e,t,r)=>t in o?t:r in o?r:t,a=document.querySelectorAll(':is(header,nav,main,aside,footer,section,form,[role=banner],[role=navigation],[role=main],[role=complementary],[role=contentinfo],[role=form],[role=search],[role=region])');for(const e of a){const a=e.getAttribute('role'),n=r(0,e.tagName.toLowerCase(),a);t(e,n,o[n])}})(),(e=>{const r=(e,t,r)=>t in o?t:('heading'===r&&(t=`heading ${e.getAttribute('aria-level')||'2'}`),t),a=document.querySelectorAll(':is(h1,h2,h3,h4,h5,h6,[role=heading])');for(const e of a){const a=e.getAttribute('role'),n=r(e,e.tagName.toLowerCase(),a);t(e,n,o[n]||'#c00')}})(),(e=>{const o=document.createElement('style');o.id='a11y-overlay',o.textContent='.-js-overlay{position:relative}.-js-overlay-border{position:absolute;inset:0;outline:2px solid var(--overlay-bg-color,#000);outline-offset:-2px;pointer-events:none;width:100%}.-js-overlay-border::after{all:unset;background-color:var(--overlay-bg-color,#000);content:var(--overlay-text, \'???\');position:absolute;top:0;right:0;color:var(--overlay-color,#fff);font-size:12px;font-weight:400;letter-spacing:.03em;text-shadow:0 0 1px #000;padding:2px 4px 1px}',document.head.appendChild(o)})()})();">Highlight landmarks and headings</a></p>
      <p>Or, create a bookmark, and copy the JavaScript into its URL.</p>
      
      <details>
        <summary>The JavaScript</summary>
        <figure>
          <figcaption id=bookmrklet>Copy into a bookmarks URL:</figcaption>
          <pre class="language-css" contenteditable spellcheck="false" role="textbox" aria-multiline="true" aria-labelledby="bookmrklet"><code>javascript:const outliner=(e=&gt;{'use strict';const o={header:'#eb0000',banner:'#eb0000',aside:'#8a7500',complementary:'#8a7500',footer:'#268500',contentinfo:'#268500',form:'#062',search:'#062',main:'#0076d1',nav:'#8a7500',navigation:'#8a7500',section:'#8352ff',region:'#8352ff',h1:'#008a27','heading 1':'#008a27',h2:'#007cad','heading 2':'#007cad',h3:'#8352ff','heading 3':'#8352ff',h4:'#db009d','heading 4':'#db009d',h5:'#d63d00','heading 5':'#d63d00',h6:'#5b8000','heading 6':'#5b8000'},t=(e,o,t)=&gt;{'static'!==getComputedStyle(e).position||e.classList.add('-js-overlay');const r=((e,o)=&gt;{const t=document.createElement(e);return t.className=o,t})('span','-js-overlay-border');r.style.setProperty('--overlay-bg-color',t),r.style.setProperty('--overlay-color','#fff'),r.style.setProperty('--overlay-text','\''+o+'\''),e.appendChild(r)};(e=&gt;{const r=(e,t,r)=&gt;t in o?t:r in o?r:t,a=document.querySelectorAll(':is(header,nav,main,aside,footer,section,form,[role=banner],[role=navigation],[role=main],[role=complementary],[role=contentinfo],[role=form],[role=search],[role=region])');for(const e of a){const a=e.getAttribute('role'),n=r(0,e.tagName.toLowerCase(),a);t(e,n,o[n])}})(),(e=&gt;{const r=(e,t,r)=&gt;t in o?t:('heading'===r&amp;&amp;(t=`heading ${e.getAttribute('aria-level')||'2'}`),t),a=document.querySelectorAll(':is(h1,h2,h3,h4,h5,h6,[role=heading])');for(const e of a){const a=e.getAttribute('role'),n=r(e,e.tagName.toLowerCase(),a);t(e,n,o[n]||'#c00')}})(),(e=&gt;{const o=document.createElement('style');o.id='a11y-overlay',o.textContent='.-js-overlay{position:relative}.-js-overlay-border{position:absolute;inset:0;outline:2px solid var(--overlay-bg-color,#000);outline-offset:-2px;pointer-events:none;width:100%}.-js-overlay-border::after{all:unset;background-color:var(--overlay-bg-color,#000);content:var(--overlay-text, \'???\');position:absolute;top:0;right:0;color:var(--overlay-color,#fff);font-size:12px;font-weight:400;letter-spacing:.03em;text-shadow:0 0 1px #000;padding:2px 4px 1px}',document.head.appendChild(o)})()})();
</code></pre>
        </figure>
      </details>
      
      <p>The bookmarklet is completely self-contained, does not reference other URLs, and can be used safely on pages that have strict content security policies.</p>

      
      <h2>1.3.1 - Info and Relationships</h2>
      
      <p>Information, structure, and relationships conveyed through presentation can be programmatically determined or are available in text.</p>
      <p></p>
      <ul>
        <li>Use landmarks: HTML elements: nav, main, header, footer etc. Or, use Aria roles: navigation, main, banner, contentinfo, etc.</li>
        <li>Label landmarks (<code>aria-label</code> or <code>aria-labelledby</code>) if there is more than one with the same role on the page.</li>
        <li>Use HTML headings <code>h1</code> to <code>h6</code> wherever possible, if not then use <code>role="heading"</code> <code>aria-level="[1, 2, 3, 4, 5, 6, 7, &hellip;]"</code></li>
        <li>Use <code>fieldset</code> and <code>legend</code> or <code>role="group"</code> <code>aria-labelledby="heading id"</code>. Add <code>aria-describedby="description id"</code> if more detail required.</li>
        <li>Ensure every <code>input</code> has a <code>label</code> to describe the input/control</li>
        <li>Ensure tables are used for data layout only, and each has a <code>caption</code> and scoped table headings (th).</li>
        <li>Use lists where appropriate.</li>
        <li>Use buttons to do something, and links to go somewhere.</li>
      </ul>
      <p><a href="https://www.w3.org/WAI/WCAG21/Understanding/info-and-relationships.html" target=_blank>Understanding 1.3.1</a></p>
    </figure>

  </main>
</body>

</html>
!

CSS 

              
                body {
  font-family: sans-serif;
  line-height: 1.5;
}
.test-elements {
}
.test-elements > section {
  padding: .5rem 1rem;
}
/* Switch off highlighting on page elements - for readability */
body > main > span,
body > main > div > h2 > span,
main > header > span,
main > header > div > h1 > span,
.test-elements > section > span {
  display: none;
}
section > header {
  border: none;
}
.test-elements > section > * {
  display: block;
  font-size: 1rem;
  font-weight: normal;
  margin: .5rem 0 0;
  padding: .125rem 0 0 .5rem;
}
.test-elements :is(aside,footer,form,main,nav,section,[role=search]),
.test-elements :is(h1,h2,h3,h4,h5,h6,[role="heading"][aria-level="7"]) {
  margin-top: 1.5rem;
}
.test-elements :first-child {
  margin-top: 0;
}


/* Highlighting */

/* Disabled here but added through JS:

.-js-overlay {
  position: relative;
}
.-js-overlay-border {
  position: absolute;
  inset: 0;
  outline: 2px solid var(--overlay-bg-color, #000);
  outline-offset: -2px;
  pointer-events: none;
  width: 100%;
}
.-js-overlay-border::after {
  all: unset;
  background-color: var(--overlay-bg-color, #000);
  content: var(--overlay-text, '???');
  position: absolute;
  top: 0;
  right: 0;
  color: var(--overlay-color, #fff);
  font-size: 12px;
  font-weight: normal;
  letter-spacing: .03em;
  text-shadow: 0 0 1px #000;
  padding: 2px 4px 1px;
}

*/
!

JS 

              
                console.clear();

const outliner = (_ => {
  'use strict';

  // Colours generated by :https://codepen.io/2kool2/pen/ExQKJZa
  // Set of 7 and 6 colours with different offsets */

  const colorText = "#fff";

  const colors = {
    'header' : '#eb0000',
    'banner' : '#eb0000',

    'aside' : '#8a7500',
    'complementary' : '#8a7500',

    'footer' : '#268500',
    'contentinfo' : '#268500',

    'form' : '#062',
    'search' : '#040',

    'main' : '#0076d1',

    'nav' : '#8a7500',
    'navigation' : '#8a7500',

    'section' : '#8352ff',
    'region' : '#8352ff',

    'h1' : '#008a27',
    'heading 1' : '#008a27',

    'h2' : '#007cad',
    'heading 2' : '#007cad',

    'h3' : '#8352ff',
    'heading 3' : '#8352ff',

    'h4' : '#db009d',
    'heading 4' : '#db009d',

    'h5' : '#d63d00',
    'heading 5' : '#d63d00',

    'h6' : '#5b8000',
    'heading 6' : '#5b8000'
  };

  const createElement = (elem, clss) => {
    const element = document.createElement(elem);
    element.className = clss;
    return element;
  };

  const addOverlay = (elem, text, colorBg) => {
    const hasPosition = getComputedStyle(elem).position !== 'static';
    if (!hasPosition) elem.classList.add('-js-overlay');
    const span = createElement('span', '-js-overlay-border');
    span.style.setProperty('--overlay-bg-color', colorBg);
    span.style.setProperty('--overlay-color', colorText);
    span.style.setProperty('--overlay-text', '"' + text + '"');
    elem.appendChild(span);
  }

  const outlineLandmarks = (_ => {

    const groupQuery = ':is(header,nav,main,aside,footer,section,form,[role=banner],[role=navigation],[role=main],[role=complementary],[role=contentinfo],[role=form],[role=search],[role=region])';

    const getText = (elem, text, role) => {
      if (text in colors) return text;
      return (role in colors) ? role : text;
    };

    const group = document.querySelectorAll(groupQuery);
    for (const elem of group) {
      const role = elem.getAttribute('role');
      const tag = elem.tagName.toLowerCase();
      const text = getText(elem, tag, role);
      addOverlay(elem, text, colors[text]);
    }

  })();


  const outlineHeadings = (_ => {

    const groupQuery = ':is(h1,h2,h3,h4,h5,h6,[role=heading])';

    const getText = (elem, text, role) => {
      if (text in colors) return text;
      if (role === 'heading') {
        text = `heading ${elem.getAttribute('aria-level') || '2'}`;
      }
      return text;
    };

    const group = document.querySelectorAll(groupQuery);
    for (const elem of group) {
      const role = elem.getAttribute('role');
      const tag = elem.tagName.toLowerCase();
      const text = getText(elem, tag, role);
      addOverlay(elem, text, colors[text] || '#c00');
    }

  })();
  
  const addStyles = (_ => {
    const style = document.createElement('style');
    style.id = 'a11y-overlay';
    style.textContent = `.-js-overlay{position:relative}.-js-overlay-border{position:absolute;inset:0;outline:2px solid var(--overlay-bg-color,#000);outline-offset:-2px;pointer-events:none;width:100%}.-js-overlay-border::after{all:unset;background-color:var(--overlay-bg-color,#000);content:var(--overlay-text, '???');position:absolute;top:0;right:0;color:var(--overlay-color,#fff);font-size:12px;font-weight:700;letter-spacing:.03em;text-shadow:0 0 1px #000;padding:2px 4px 1px}`;
    document.head.appendChild(style);
  })();

})();


// Minified JS (2015 bytes) for bookmarklet:
// javascript:const outliner=(e=>{'use strict';const o={header:'#eb0000',banner:'#eb0000',aside:'#8a7500',complementary:'#8a7500',footer:'#268500',contentinfo:'#268500',form:'#062',search:'#062',main:'#0076d1',nav:'#8a7500',navigation:'#8a7500',section:'#8352ff',region:'#8352ff',h1:'#008a27','heading 1':'#008a27',h2:'#007cad','heading 2':'#007cad',h3:'#8352ff','heading 3':'#8352ff',h4:'#db009d','heading 4':'#db009d',h5:'#d63d00','heading 5':'#d63d00',h6:'#5b8000','heading 6':'#5b8000'},t=(e,o,t)=>{'static'!==getComputedStyle(e).position||e.classList.add('-js-overlay');const r=((e,o)=>{const t=document.createElement(e);return t.className=o,t})('span','-js-overlay-border');r.style.setProperty('--overlay-bg-color',t),r.style.setProperty('--overlay-color','#fff'),r.style.setProperty('--overlay-text','\''+o+'\''),e.appendChild(r)};(e=>{const r=(e,t,r)=>t in o?t:r in o?r:t,a=document.querySelectorAll(':is(header,nav,main,aside,footer,section,form,[role=banner],[role=navigation],[role=main],[role=complementary],[role=contentinfo],[role=form],[role=search],[role=region])');for(const e of a){const a=e.getAttribute('role'),n=r(0,e.tagName.toLowerCase(),a);t(e,n,o[n])}})(),(e=>{const r=(e,t,r)=>t in o?t:('heading'===r&&(t=`heading ${e.getAttribute('aria-level')||'2'}`),t),a=document.querySelectorAll(':is(h1,h2,h3,h4,h5,h6,[role=heading])');for(const e of a){const a=e.getAttribute('role'),n=r(e,e.tagName.toLowerCase(),a);t(e,n,o[n]||'#c00')}})(),(e=>{const o=document.createElement('style');o.id='a11y-overlay',o.textContent='.-js-overlay{position:relative}.-js-overlay-border{position:absolute;inset:0;outline:2px solid var(--overlay-bg-color,#000);outline-offset:-2px;pointer-events:none;width:100%}.-js-overlay-border::after{all:unset;background-color:var(--overlay-bg-color,#000);content:var(--overlay-text, \'???\');position:absolute;top:0;right:0;color:var(--overlay-color,#fff);font-size:12px;font-weight:400;letter-spacing:.03em;text-shadow:0 0 1px #000;padding:2px 4px 1px}',document.head.appendChild(o)})()})();
!
999px

Console