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Iframe with interactive elements is not excluded from tab-order


This rule checks that iframe elements which contain an interactive (tabbable) element are not excluded from sequential focus navigation.


This rule applies to any iframe element that is not inert and that contains at least one element for which all the following are true:

An element is contained in a nested browsing context if its owner document is the container document of the nested browsing context.


The test target does not have a negative number as a tabindex attribute value.


This rule assumes that interactive content inside iframe elements is used to provide functionality. If the interactive content does not provide functionality, for example a button that does nothing when clicked, success criterion 2.1.1 may be satisfied, even if the rule is failed.

Accessibility Support

There are no accessibility support issues known.


Setting the tabindex attribute of an iframe element to a negative value effectively excludes its content from the tab-order of the page. A button may be in the tab-order of an iframe, but if the iframe itself is taken from the tab-order, the button is effectively keyboard inaccessible.

Each document, including documents inside an iframe, has its own sequential focus navigation order. These focus orders are combined to get the page’s global tab-order (called the flattened tabindex-ordered focus navigation scope). For an iframe with a negative tabindex, its sequential focus navigation order is not included in the page’s global tab-order (as a consequence for the rules to build the tabindex-ordered focus navigation scope).


Accessibility Requirements Mapping

Input Aspects

The following aspects are required in using this rule.

Test Cases


Passed Example 1

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This iframe element does not have a tabindex attribute value that is a negative number

<iframe srcdoc="<a href='/'>Home</a>"></iframe>

Passed Example 2

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This iframe element does not have a tabindex attribute value that is a negative number

<iframe tabindex="0" srcdoc="<a href='/'>Home</a>"></iframe>


Failed Example 1

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This iframe element contains a visible link that is part of its sequential focus navigation order, and has a negative tabindex.

<iframe tabindex="-1" srcdoc="<a href='/'>Home</a>"></iframe>


Inapplicable Example 1

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This iframe element contains no content that is part of its sequential focus navigation order.

<iframe tabindex="-1" srcdoc="<h1>Hello world</h1>"></iframe>

Inapplicable Example 2

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This iframe element contains no visible content because the iframe is hidden.

<iframe tabindex="-1" hidden srcdoc="<a href='/'>Home</a>"></iframe>

Inapplicable Example 3

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This iframe element contains no visible content because of the small size of the iframe.

<iframe tabindex="-1" width="1" height="1" srcdoc="<a href='/'>Home</a>"></iframe>

Inapplicable Example 4

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This iframe element contains a link that is not part of its sequential focus navigation order because of its own tabindex.

<iframe tabindex="-1" srcdoc="<a href='/' tabindex='-1'>Home</a>"></iframe>

Inapplicable Example 5

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This iframe element is inert because of its own inert attribute value.

<iframe tabindex="-1" inert srcdoc="<a href='/'>Home</a>"></iframe>

Inapplicable Example 6

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Once the “Privacy policy details” button is activated, the iframe element becomes inert because of the showModal() method, which causes the iframe to be blocked by a modal.

<iframe id="myFrame" title="Links" srcdoc="<a href='/'>Home</a>"></iframe>
	<button id="ppButton" onclick="openDialog()">Privacy policy details</button>
<dialog id="ppDialog" aria-labelledby="dialogLabel">
	<h2 id="dialogLabel">Privacy Policy</h2>
	<p>We store no data.</p>
	<button id="cancel" onclick="ppDialog.close()">Cancel</button>
	const openDialog = () => {
		myFrame.tabIndex = '-1'
	ppDialog.addEventListener('close', () => myFrame.tabIndex = 0)
	window.addEventListener('DOMContentLoaded', openDialog);


Attribute value

The attribute value of a content attribute set on an HTML element is the value that the attribute gets after being parsed and computed according to specifications. It may differ from the value that is actually written in the HTML code due to trimming whitespace or non-digits characters, default values, or case-insensitivity.

Some notable case of attribute value, among others:

This list is not exhaustive, and only serves as an illustration for some of the most common cases.

The attribute value of an IDL attribute is the value returned on getting it. Note that when an IDL attribute reflects a content attribute, they have the same attribute value.


An HTML or SVG element is inert if:

Namespaced Element

An element with a specific namespaceURI value from HTML namespaces. For example an “SVG element” is any element with the “SVG namespace”, which is

Namespaced elements are not limited to elements described in a specification. They also include custom elements. Elements such as a and title have a different namespace depending on where they are used. For example a title in an HTML page usually has the HTML namespace. When used in an svg element, a title element has the SVG namespace instead.


An outcome is a conclusion that comes from evaluating an ACT Rule on a test subject or one of its constituent test target. An outcome can be one of the three following types:

Note: A rule has one passed or failed outcome for every test target. When there are no test targets the rule has one inapplicable outcome. This means that each test subject will have one or more outcomes.

Note: Implementations using the EARL10-Schema can express the outcome with the outcome property. In addition to passed, failed and inapplicable, EARL 1.0 also defined an incomplete outcome. While this cannot be the outcome of an ACT Rule when applied in its entirety, it often happens that rules are only partially evaluated. For example, when applicability was automated, but the expectations have to be evaluated manually. Such “interim” results can be expressed with the incomplete outcome.


Content perceivable through sight.

Content is considered visible if making it fully transparent would result in a difference in the pixels rendered for any part of the document that is currently within the viewport or can be brought into the viewport via scrolling.

Content is defined in WCAG.

For more details, see examples of visible.

Rule Versions

  1. Latest version, 20 December 2023 (compare)
    • Added inapplicable example 5 and 6
  2. Previous version, 30 August 2023


This section is not part of the official rule. It is populated dynamically and not accounted for in the change history or the last modified date.

Implementation Type Consistency Report
QualWeb 3.0.0 Automated tool Consistent QualWeb Report
SortSite 6.45 Automated tool Consistent SortSite Report
Total Validator 17.4.0 Linter Consistent Total Validator Report
Total Validator (+Browser) 17.4.0 Automated tool Consistent Total Validator (+Browser) Report
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