Scrollable content can be reached with sequential focus navigation
Applicability
This rule applies to any [HTML element][] that has [visible][] [children][] in the [flat tree][], and for which at least one of the following is true:
the element has a [horizontal scroll distance][scrollable] greater than the [computed][] [left][padding-left] or [right padding][padding-right] of the element; or
the element has a [vertical scroll distance][scrollable] greater than the [computed][] [top][padding-top] or [bottom padding][padding-bottom] of the element.
Expectation
Each test target is either included in [sequential focus navigation][] or has a [descendant][] in the [flat tree][] that is included in [sequential focus navigation][].
Assumptions
This rule assumes that all [scrollable elements][scrollable] with visible content need to be keyboard accessible. [Scrollable elements][scrollable] that do not need to be keyboard accessible, perhaps because their content is [purely decorative][], the scroll area is whitespace, or because scroll can be controlled in some other keyboard accessible way such as through a button or custom scrollbar, may fail this rule but still satisfy [success criterion 2.1.1 Keyboard][].
Accessibility Support
Some browsers will automatically make any [scrollable element][scrollable] focusable to ensure keyboard accessibility. However, the browser does not include these elements in [sequential focus navigation][] when it has a negative number as a tabindex [attribute value][].
Some browsers restrict scrolling to the content box of elements; while others allow to scroll the full border box, hence including the element's padding. This results in some elements being scrollable with a browser but not with another.
Background
To ensure there is some element from which arrow keys can be used to control the scroll position, focus must be on or in a scrollable region. If scripts are used to prevent the keyboard events from reaching the scrollable region, this could still cause a keyboard accessibility issue. This must be tested separately.
This rule only applies to elements who scroll content in the same document. Elements such as iframes that embed other documents may also be scrollable, but for them it is the embedded document that scrolls, not the content in the same document. Such scenarios are tested separately with rules such as Iframe with negative tabindex has no interactive elements.
This [scrollable][] section element is included in [sequential focus navigation][] because it has a tabindex attribute set to 0.
<section style="height: 100px; width: 500px; overflow: scroll;" tabindex="0">
<h1>WCAG 2.1 Abstract</h1>
<p>
Web Content Accessibility Guidelines (WCAG) 2.1 covers a wide range of recommendations for making Web content more
accessible. Following these guidelines will make content more accessible to a wider range of people with
disabilities, including accommodations for blindness and low vision, deafness and hearing loss, limited movement,
speech disabilities, photosensitivity, and combinations of these, and some accommodation for learning disabilities
and cognitive limitations; but will not address every user need for people with these disabilities. These guidelines
address accessibility of web content on desktops, laptops, tablets, and mobile devices. Following these guidelines
will also often make Web content more usable to users in general.
</p>
</section>
Passed Example 2
This [scrollable][] section element contains a link that is included in [sequential focus navigation][].
<section style="height: 100px; width: 500px; overflow: scroll;">
<h1>
<a href="https://www.w3.org/TR/WCAG22/#abstract">
WCAG 2.1 Abstract
</a>
</h1>
<p>
Web Content Accessibility Guidelines (WCAG) 2.1 covers a wide range of recommendations for making Web content more
accessible. Following these guidelines will make content more accessible to a wider range of people with
disabilities, including accommodations for blindness and low vision, deafness and hearing loss, limited movement,
speech disabilities, photosensitivity, and combinations of these, and some accommodation for learning disabilities
and cognitive limitations; but will not address every user need for people with these disabilities. These guidelines
address accessibility of web content on desktops, laptops, tablets, and mobile devices. Following these guidelines
will also often make Web content more usable to users in general.
</p>
</section>
Failed
Failed Example 1
This [vertically scrollable][scrollable] section element is not included in [sequential focus navigation][], nor does it have any [descendants][descendant] that are.
<section style="height: 100px; width: 500px; overflow-y: scroll">
<h1>WCAG 2.1 Abstract</h1>
<p>
Web Content Accessibility Guidelines (WCAG) 2.1 covers a wide range of recommendations for making Web content more
accessible. Following these guidelines will make content more accessible to a wider range of people with
disabilities, including accommodations for blindness and low vision, deafness and hearing loss, limited movement,
speech disabilities, photosensitivity, and combinations of these, and some accommodation for learning disabilities
and cognitive limitations; but will not address every user need for people with these disabilities. These guidelines
address accessibility of web content on desktops, laptops, tablets, and mobile devices. Following these guidelines
will also often make Web content more usable to users in general.
</p>
</section>
Failed Example 2
This [horizontally scrollable][scrollable] section element is not included in [sequential focus navigation][], nor does it have any [descendants][descendant] that are.
This section element has a [computed][] [overflow][] of visible. Because of this its [scroll distance][scrollable] will be 0, regardless of the element's content.
<section style="height: 95px; width: 500px;">
<h1>WCAG 2.1 Abstract</h1>
<p>
Web Content Accessibility Guidelines (WCAG) 2.1 covers a wide range of recommendations for making Web content more
accessible. Following these guidelines will make content more accessible to a wider range of people with
disabilities, including accommodations for blindness and low vision, deafness and hearing loss, limited movement,
speech disabilities, photosensitivity, and combinations of these, and some accommodation for learning disabilities
and cognitive limitations; but will not address every user need for people with these disabilities. These guidelines
address accessibility of web content on desktops, laptops, tablets, and mobile devices. Following these guidelines
will also often make Web content more usable to users in general.
</p>
</section>
Inapplicable Example 2
This section element has a [scroll distance][scrollable] of 0 in both directions.
This section element is not [scrollable][] because it has a [computed][] [overflow][] of hidden.
<h1>
<a href="https://www.w3.org/TR/WCAG22/#abstract">
WCAG 2.1 Abstract
</a>
</h1>
<section style="height: 95px; width: 500px; overflow: hidden;">
<p>
Web Content Accessibility Guidelines (WCAG) 2.1 covers a wide range of recommendations for making Web content more
accessible. Following these guidelines will make content more accessible to a wider range of people with
disabilities, including accommodations for blindness and low vision, deafness and hearing loss, limited movement,
speech disabilities, photosensitivity, and combinations of these, and some accommodation for learning disabilities
and cognitive limitations; but will not address every user need for people with these disabilities. These guidelines
address accessibility of web content on desktops, laptops, tablets, and mobile devices. Following these guidelines
will also often make Web content more usable to users in general.
</p>
</section>
Inapplicable Example 4
This [scrollable][] section element has no [visible][] content.
<p>This is what a scrollbar looks like:</p>
<section style="height: 20px; width: 500px; overflow-x:scroll;">
<div style="width: 1000px; height: 1px;"></div>
</section>
Inapplicable Example 5
This section element has a [horizontal scroll distance][scrollable] that is less than its horizontal [padding][], and [vertical scroll distance][scrollable] that is less than its vertical [padding][].
<section style="height: 210px; width: 530px; overflow: scroll; padding: 30px 0 30px 30px;">
<div role="heading" aria-level="1">WCAG 2.1 Abstract</div>
<div style="width: 520px">
Web Content Accessibility Guidelines (WCAG) 2.1 covers a wide range of recommendations for making Web content more
accessible. Following these guidelines will make content more accessible to a wider range of people with
disabilities, including accommodations for blindness and low vision, deafness and hearing loss, limited movement,
speech disabilities, photosensitivity, and combinations of these, and some accommodation for learning disabilities
and cognitive limitations; but will not address every user need for people with these disabilities. These guidelines
address accessibility of web content on desktops, laptops, tablets, and mobile devices. Following these guidelines
will also often make Web content more usable to users in general.
</div>
</section>
Inapplicable Example 6
This iframe element is not a scrollable element, but instead contains a nested browsing context that is scrollable. These must be tested separately.
