HTML Guide

There can only be one visible <main> element in a document. If more are needed (for example for switching between them with JavaScript), only one can be visible, the others should be hidden toggling the hidden attribute.

Example of 2 main elements, where only one is visible:

<main>
  <h1>Active main element</h1>
  <!-- content -->
</main>

<main hidden>
  <h1>Hidden main element</h1>
  <!-- content -->
</main>

Elements with the role tab must either be a child of an element with the tablist role, or have their id part of the aria-owns property of a tablist.

An element with the tab role controls the visibility of an associated element with the tabpanel role. The common user experience pattern is a group of visual tabs above, or to the side of, a content area, and selecting a different tab changes the content and makes the selected tab more prominent than the other tabs.

Example:

<div class="tabs">
  <div role="tablist" aria-label="Sample Tabs">
    <button role="tab" aria-selected="true" aria-controls="panel-1" id="tab-1" tabindex="0">
          First Tab
    </button>
    <button role="tab" aria-selected="false" aria-controls="panel-2" id="tab-2" tabindex="-1">
          Second Tab
     </button>
  </div>
  <div id="panel-1" role="tabpanel" tabindex="0" aria-labelledby="tab-1">
    <p>Content for the first panel</p>
  </div>
  <div id="panel-2" role="tabpanel" tabindex="0" aria-labelledby="tab-2" hidden>
    <p>Content for the second panel</p>
  </div>
</div>

The aria-* attributes are part of the WAI-ARIA (Web Accessibility Initiative-Accessible Rich Internet Applications) suite. They are used to improve the accessibility of web pages. However, when we use an input element with a type attribute whose value is hidden, we imply that the element is invisible and has no interaction with the user. Therefore, it doesn’t make sense to add aria-* attributes to it.

To fix this issue, you need to remove the aria-* attributes from the input element with type=hidden. Here is an example:

<!-- Wrong code -->
<input type="hidden" name="referer" value="https://example.com" aria-invalid="false">

<!-- Correct code -->
<input type="hidden" name="referer" value="https://example.com">

Due to an issue in the W3C validator, this is identified as an error but it’s not. This issue has been notified, and we’ll update our validator as soon as there’s a fix.

According to the WAI-ARIA 1.2 spec:

The aria-setsize property defines the number of items in the current set of listitems or treeitems. Not required if all elements in the set are present in the DOM.

Authors MUST set the value of aria-setsize to an integer equal to the number of items in the set. If the total number of items is unknown, authors SHOULD set the value of aria-setsize to -1.

The alert role can be used to tell the user an element has been dynamically updated. Screen readers will instantly start reading out the updated content when the role is added. The element <ul> doesn’t accept this kind of role, consider using other element like <p> or <div>.

The alert role is used to communicate an important and usually time-sensitive message to the user. When this role is added to an element, the browser will send out an accessible alert event to assistive technology products which can then notify the user about it. The alert role is most useful for information that requires the user’s immediate attention.

The aria-expanded attribute can only be true, false, or undefined.

This attribute indicates whether a grouping element is expanded or collapsed.

There’s no role in ARIA named presentational, you probably mean presentation.

The presentation role and its synonym none remove an element’s implicit ARIA semantics from being exposed to the accessibility tree.

The content of the element will still be available to assistive technologies; it is only the semantics of the container — and in some instance, required associated descendants — which will no longer expose their mappings to the accessibility API.

<input> elements can’t have a search role. Instead, try with <input type="search">.

<input> elements of type search are text fields designed for the user to enter search queries into. These are functionally identical to text inputs, but may be styled differently depending on the user agent.

The search role is a landmark. Landmarks can be used by assistive technology to quickly identify and navigate to large sections of the document. The search role is added to the container element that encompasses the items and objects that, as a whole, combine to create search functionality. When a <form> is a search form, use the search role on the form.

Example of a search form:

<form role="search">
  <label for="search-input">Search this site</label>
  <input type="search" id="search-input" name="search">
  <input value="Submit" type="submit">
</form>

The only accepted values for the aria-current property are page, step, location, date, time, true and false.

A non-null aria-current state on an element indicates that this element represents the current item within a container or set of related elements.

When you have a group of related elements, such as several links in a breadcrumb or steps in a multi-step flow, with one element in the group styled differently from the others to indicate to the sighted user that this is the current element within its group, the aria-current should be used to inform the assistive technology user what has been indicated via styling.

In its simplest form, you only need to add aria-current="true" to the element that you wish to mark as the current element of a group, for example:

<nav>
  <ol>
    <li>
      <a href="/page1">Page 1</a>
    </li>
    <li>
      <a href="/page2" aria-current="true">Page 2</a>
    </li>
    <li>
      <a href="/page3">Page 3</a>
    </li>
  </ol>
</nav>

If you can, use the values page, step, location, date or time instead of true to indicate the nature of the current element:

page

Represents the current page within a set of pages such as the link to the current document in a breadcrumb.

step

Represents the current step within a process such as the current step in an enumerated multi step checkout flow.

location

Represents the current location within an environment or context such as the image that is visually highlighted as the current component of a flow chart.

date

Represents the current date within a collection of dates such as the current date within a calendar.

time

Represents the current time within a set of times such as the current time within a timetable.

For example, here we use page instead of true.

<nav>
  <ol>
    <li>
      <a href="/page1">Page 1</a>
    </li>
    <li>
      <a href="/page2" aria-current="page">Page 2</a>
    </li>
    <li>
      <a href="/page3">Page 3</a>
    </li>
  </ol>
</nav>

If you want to indicate that an element is not the current element, you can use the false value or just skip the aria-current property entirely on the element.

Using a blank string is not a valid value for this property, so instead of this:

 <a href="/page3" aria-current="">Page 3</a>

you can use false:

 <a href="/page3" aria-current="false">Page 3</a>

or, better yet, skip the property entirely:

 <a href="/page3">Page 3</a>

The only accepted value for the aria-required property is true.

The aria-required attribute indicates that user input is required on the element before a form may be submitted.

When a semantic HTML <input>, <select>, or <textarea> must have a value, it should have the required attribute applied to it. When form controls are created using non-semantic elements, such as a <div> with a role of checkbox, the aria-required attribute should be included, with a value of true, to indicate to assistive technologies that user input is required on the element for the form to be submittable.

Example:

<div id="email_label">Email Address *</div>
<div
  role="textbox"
  contenteditable
  aria-labelledby="email_label"
  aria-required="true"
  id="email"></div>