HTML Guide

A button element, or an element with the role=button attribute, is not allowed to be nested inside an <a> element.

When you encounter the issue where the <a> element is nested inside an element with role="button", it’s important to understand that this can lead to accessibility conflicts. The role="button" indicates that the element is interactive, similar to a button. Nesting an <a> (which is also an interactive element) inside it can confuse assistive technologies.

How to Fix This Issue

You should either change the structure so that the <a> is not inside the button or change the role of the button to avoid this violation. Here are two common approaches to resolve the issue:

Option 1: Remove the <a> Tag

Replace the <a> tag with an appropriate action directly inside the element with role="button".

Example Before:

<div role="button">
  <a href="#link">Click here</a>
</div>

Example After:

<div role="button" tabindex="0" onclick="location.href='#link';">
  Click here
</div>

Here, we use JavaScript to navigate to the link when the div is clicked.

Option 2: Remove the role="button"

If the <a> tag is sufficient by itself, you can remove the role="button" from the surrounding element.

Example Before:

<div role="button">
  <a href="#link">Click here</a>
</div>

Example After:

<a href="#link">Click here</a>

This maintains the desired navigation without creating a conflict between the button and link semantics.

An a element is not allowed to be nested inside a <button> element, or an element with the role=button attribute.

An <a> element cannot contain a descendant element with the attribute tabindex.

A button element cannot contain a descendant element with the attribute tabindex.

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

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

An element like <h1>, <h2>, etc., used to define a heading, does not accept the button role.

The following HTML code is invalid because the <h2> element can’t have role="button"

<h2 role="button">Some heading</h2>

Instead, you can nest the <h2> inside a <div> with that role. In this case however, browsers automatically apply role presentation to all descendant elements of any button element as it is a role that does not support semantic children.

<div role="button">
  <h2>Some heading</h2>
</div>

A <li> element, used to define a list item, does not accept the button role.

This HTML code is invalid because the <li> elements can’t have role="button":

<ul>
  <li role="button">One</li>
  <li role="button">Two</li>
</ul>

Spaces are not permitted in the href value for phone links; the phone number must be a continuous string without spaces or slashes.

The href attribute of an anchor (<a>) element defines the link’s destination. For phone numbers, the proper URI scheme is tel:, not callto:. According to the HTML standard and the WHATWG Living Standard, the phone number should contain only digits and may use plus (+) or hyphen (-) characters for formatting, but it should not include spaces or slashes.

Incorrect HTML:

<a href="callto:07142/ 12 34 5">Call us</a>

Correct HTML:

<a href="tel:0714212345">Call us</a>

With country code and optional formatting:

<a href="tel:+49714212345">Call us</a>

For best compatibility and validation, always use the tel: scheme and ensure the phone number string contains only allowed characters.

Empty aria-controls attribute values are invalid; the attribute must reference the id of one or more elements.

The aria-controls attribute is used to indicate that the element controls the referenced element(s) by their id. According to the ARIA specification and W3C HTML standard, the attribute must contain at least one valid id value, and cannot be an empty string. Leaving aria-controls="" triggers a validation error.

Correct Usage:

• Assign an id to the element being controlled.
• Set the aria-controls attribute to match that id.
• Remove aria-controls entirely if not necessary.

Incorrect Example:

<a href="#" aria-controls="">Toggle</a>

Corrected Example:

<div id="details">Some details...</div>
<a href="#" aria-controls="details">Toggle</a>

If no element is being controlled:

<a href="#">Toggle</a>