Links with identical accessible names and context serve equivalent purpose

  • Rule Type:atomic
  • Rule Id: fd3a94
  • Last modified: Apr 28, 2020
  • Accessibility Requirements Mapping:
    • 2.4.4 Link Purpose (In Context) (Level: A)
      • Learn More about 2.4.4 (Link Purpose (In Context))
      • Required for conformance to WCAG 2.0 and above on level A and above.
      • Outcome mapping:
        • Any failed outcomes: success criterion is not satisfied.
        • All passed outcomes: success criterion needs further testing.
        • An inapplicable outcome: success criterion needs further testing.

Description

This rule checks that links with identical accessible names and context resolve to the same or equivalent resources.

Applicability

This rule applies to any set of two or more HTML or SVG elements which

Note: The test target for this rule is the full set of link elements that share the same matching accessible name and programmatically determined link context.

Expectation

When followed, the links in each set of target elements resolve to the same resource or to equivalent resources.

Note: Resolving the links includes potential redirects, if the redirects happen instantly.

Assumptions

  • This rule assumes that the purpose of the links with identical accessible names and context would not be ambiguous to users in general, which is the exception mentioned in Success Criterion 2.4.4 Link Purpose (In Context). If the links are ambiguous to users in general, users of assistive technologies are not at a disadvantage when viewing the links, which makes it more of a general user experience concern than an accessibility issue.
  • This rule assumes that, within the context of the test subject, the description provided by the accessible name of a link can only accurately describe one resource (notably, homonyms alone are not used as link names). Thus, if two or more links have the same accessible name but resolve to different resources, at least one of them does not describe its purpose.
  • This rule assumes that the language of each test target can be correctly determined (either programmatically or by analyzing the content), and sufficiently understood.
  • This rule assumes that assistive technologies are exposing all links on the page in the same way no matter which document tree they are in. If an assistive technology requires the user to "enter" an iframe or a shadow tree before exposing its links, then it is possible for two links to have identical name and context but resolve to different resources without failing Success Criterion 2.4.4 Link Purpose (In Context) (if said links are in separate documents or shadow trees)

Accessibility Support

There are no major accessibility support issues known for this rule.

Background

Test Cases

Passed

Passed Example 1

Open in a new tab

These two HTML a elements have the same accessible name and context and link to the same resource.

<html lang="en">
	<p>
		Learn more (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html"
			>Contact us</a
		>) and get in touch (
		<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html">Contact us</a>)
	</p>
</html>

Passed Example 2

Open in a new tab

These two HTML a elements have the same accessible name and context, and resolve to the same resource after an instant redirect.

<html lang="en">
	<p>
		Learn more (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html"
			>Contact us</a
		>) and get in touch (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/redirect.html"
			>Contact us</a
		>)
	</p>
</html>

Passed Example 3

Open in a new tab

These two HTML a elements have the same accessible name and context, and resolve to identical resources.

<html lang="en">
	<p>
		Learn more (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html"
			>Contact us</a
		>) and get in touch (<a
			href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index-copy.html"
			>Contact us</a
		>)
	</p>
</html>

Passed Example 4

Open in a new tab

These two HTML a elements have the same accessible name and context, and resolve to pages that serve the same purpose because the content section is the same.

<html lang="en">
	<p>
		Learn more (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/about/contact.html"
			>Contact us</a
		>) and get in touch (
		<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/careers/contact.html">Contact us</a
		>)
	</p>
</html>

Passed Example 5

Open in a new tab

These two HTML a elements have the same accessible name and context, and go to pages that fulfill the same purpose in relation to the link because they contain the same relevant information.

<html lang="en">
	<p>
		Learn more (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page1.html">Call us</a
		>) and get in touch (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page2.html"
			>Call us</a
		>)
	</p>
</html>

Passed Example 6

Open in a new tab

These two HTML a elements have the same accessible name and context, and go to pages that use different layouts but have the same purpose.

<html lang="en">
	<p>
		Learn more (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page1.html"
			>Contact us</a
		>) and get in touch (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page3.html"
			>Contact us</a
		>)
	</p>
</html>

Passed Example 7

Open in a new tab

These two HTML span elements have an explicit role of link, the same accessible name, the same context, and link to the same resource.

<html lang="en">
	<p>
		<span
			role="link"
			tabindex="0"
			onclick="location='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html'"
		>
			My university
		</span>

		<span
			role="link"
			tabindex="0"
			onclick="location='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html'"
		>
			My university
		</span>
	</p>
</html>

Passed Example 8

Open in a new tab

These two SVG a and HTML a elements have the same accessible name, same context and link to the same resource.

<html lang="en">
	<p>
		<a href="http://facebook.com">Follow us</a>

		<svg viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
			<a href="http://facebook.com" aria-label="Follow us">
				<circle cx="50" cy="40" r="35" />
			</a>
		</svg>
	</p>
</html>

Failed

Failed Example 1

Open in a new tab

These two HTML a elements have the same accessible name and context but go to different resources.

<html lang="en">
	<p>
		We are on social media:
		<a href="http://facebook.com">Follow us</a>
		<a href="http://twitter.com">Follow us</a>
	</p>
</html>

Failed Example 2

Open in a new tab

These two HTML a elements have the same accessible name and context. They link to web pages that are similar, but have different information in their content.

<html lang="en">
	<p>
		Learn more (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/about/contact.html"
			>Contact us</a
		>) and get in touch (
		<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/admissions/contact.html"
			>Contact us</a
		>)
	</p>
</html>

Failed Example 3

Open in a new tab

These two HTML span elements have an explicit role of link, same accessible name and context, but link to resources that offer different content.

<html lang="en">
	<p>
		Learn more (<span
			role="link"
			tabindex="0"
			onclick="location='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/about/contact.html'"
			>Contact us</span
		>) and get in touch (<span
			role="link"
			tabindex="0"
			onclick="location='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/admissions/contact.html'"
			>Contact us</span
		>)
	</p>
</html>

Failed Example 4

Open in a new tab

These two SVG a elements have the same accessible name and context but link to different resources.

<html lang="en">
	<p>
		<svg viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
			<a href="http://facebook.com" aria-label="Follow us">
				<circle cx="50" cy="40" r="35" />
			</a>

			<a href="http://twitter.com">
				<text x="50" y="90" text-anchor="middle">
					Follow us
				</text>
			</a>
		</svg>
	</p>
</html>

Failed Example 5

Open in a new tab

These two HTML a elements with the same accessible name and context resolve to the same resource after redirect, but the redirect is not instant.

<html lang="en">
	<p>
		Learn more (<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html"
			>Contact us</a
		>) and get in touch (<a
			href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/redirect1.html"
			>Contact us</a
		>)
	</p>
</html>

Inapplicable

Inapplicable Example 1

Open in a new tab

These HTML a and area elements do not have a role of link.

<html lang="en">
	<a>Link text</a>
	<area aria-label="Link text" />
</html>

Inapplicable Example 2

Open in a new tab

These two HTML a elements have different accessible names.

Note: It is a best practice for Success Criterion 2.4.4: Link Purpose (In Context) that identical links have identical accessible names. This is however not a requirement.

<html lang="en">
	<p>
		<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/about/contact.html">Reach out</a>
		<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/about/contact.html">Contact us</a>
	</p>
</html>

Inapplicable Example 3

Open in a new tab

These two HTML a elements have the same accessible name and link to the same resource but different programmatically determined link contexts.

<html lang="en">
	<ul>
		<li>
			To learn more about us:
			<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html">Contact us</a>
		</li>
		<li>
			To get in touch with us:
			<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html">Contact us</a>
		</li>
	</ul>
</html>

Inapplicable Example 4

Open in a new tab

These two span elements do not have a semantic role of link.

<html lang="en">
	<p>
		Learn more (<span
			onclick="location='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page1.html'"
			>Contact Us </span
		>) and get in touch (<span
			onclick="location='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page2.html'"
			>Contact Us </span
		>)
	</p>
</html>

Inapplicable Example 5

Open in a new tab

The second HTML a element has an empty accessible name.

<a href="http://facebook.com">Follow us</a> <a href="http://facebook.com"><img src="facebook.jpg"/></a>

Glossary

Accessible Name

The accessible name is the programmatically determined name of a user interface element that is included in the accessibility tree.

The accessible name is calculated using the accessible name and description computation.

For native markup languages, such as HTML and SVG, additional information on how to calculate the accessible name can be found in HTML Accessibility API Mappings 1.0, Accessible Name and Description Computation (working draft) and SVG Accessibility API Mappings, Name and Description (working draft).

Note: As per the accessible name and description computation, each element always has an accessible name. When no accessible name is provided, the element will nonetheless be assigned an empty ("") one.

Note: As per the accessible name and description computation, accessible names are flat string trimmed of leading and trailing whitespace. Notably, it is not possible for a non-empty accessible name to be composed only of whitespace since these must be trimmed.

Accessibility Support for Accessible Name

  • Because the accessible name and description computation is not clear about which whitespace are considered, browsers behave differently when trimming and flattening the accessible name. For example, some browsers completely trim non-breaking spaces while some keep them in the accessible name.
  • There exists a popular browser which does not perform the same trimming and flattening depending whether the accessible name comes from content, an aria-label attribute, or an alt attribute.
  • There exists a popular browser which assign no accessible name (null) when none is provided, instead of assigned an empty accessible name ("").

Examples for Accessible Name

Note: The examples presented here are non-normative and not testable. They serve to illustrate some common pitfalls about the definition and to help implementers of ACT rules understand it.

The input elements have an accessible name of, respectively, "Billing Name" and "Billing Address". These accessible names are given by the aria-labelledby attributes and associated elements.

<div id="myBillingId">Billing</div>

<div>
	<div id="myNameId">Name</div>
	<input type="text" aria-labelledby="myBillingId myNameId" />
</div>
<div>
	<div id="myAddressId">Address</div>
	<input type="text" aria-labelledby="myBillingId myAddressId" />
</div>

This button element has an accessible name of "Share ACT rules" given by its aria-label attribute.

<button aria-label="Share ACT rules">Share</button>

This img element has an accessible name of "ACT rules" given by its alt attribute.

<img src="#" alt="ACT rules" />

The button element has an accessible name of "Share ACT rules" given by the enclosing label element (implicit label)

<label>Share ACT rules<button>Share</button></label>

The button element has an accessible name of "Share ACT rules" given by the associated label element (explicit label)

<label for="act-rules">Share ACT rules</label><button id="act-rules"></button>

This a element has an accessible name of "ACT rules" given from its content. Note that not all semantic roles allow name from content.

<a href="https://act-rules.github.io/">ACT rules</a>

This span element has an empty accessible name ("") because span does not allow name from content.

<span>ACT rules</span>

This span element has an empty accessible name ("") because span is not a labelable element.

<label>ACT rules<span></span></label>

Note: When the same element can have an accessible name from several sources, the order of precedence is: aria-labelledby, aria-label, own attributes, label element, name from content. The examples here are listed in the same order.

Note: For more examples of accessible name computation, including many tricky cases, check the Accessible Name Testable Statements.

Equivalent resource

Non-identical resources can still be equivalent resources by equally complying to the expectation formed by the user when navigating to them, thus serving an equivalent purpose. This would usually involve that the advertised key content is the same.

Web pages and documents (e.g. PDFs, office formats etc.) may be equivalent resources, even if the resources:

  • are located on different URLs, including different domains
  • present different navigation options, e.g. through bread crumbs or local sub menus
  • contain different amounts of information and/or differently worded information
  • use different layouts.

If all resources cover the user's expectations equally well, the resources are considered to be equivalent.

Note: The user's expectations for the resource can be formed by different things, e.g. the name of the link leading to the resource, with or without the context around the link. This depends on the accessibility requirement that is tested.

Note: If the same content is presented in different formats or languages, the format or language itself is often part of the purpose of the content, e.g. an article as both HTML and PDF, an image in different sizes, or an article in two different languages. If getting the same content in different formats or languages is the purpose of having separate links, the resources are not equivalent.

Explicit Semantic Role

The explicit semantic role of an element is determined by its role attribute (if any).

The role attribute takes a list of tokens. The explicit semantic role is the first valid role in this list. The valid roles are all non-abstract roles from WAI-ARIA Specifications. If the element has no role attribute, or if it has one with no valid role, then this element has no explicit semantic role.

Other roles may be added as they become available. Not all roles will be supported in all assistive technologies. Testers are encouraged to adjust which roles are allowed according to the accessibility support base line. For the purposes of executing test cases in all rules, it should be assumed that all roles are supported by assistive technologies so that none of the roles fail due to lack of accessibility support.

Accessibility Support for Explicit Semantic Role

Some browsers and assistive technologies treat the tokens of the role attribute as case-sensitive. Unless lowercase letters are used for the value of the role attribute, not all user agents will be able to interpret the tokens correctly. ARIA in HTML (working draft) also specifies that authors must use lowercase letters for the role and aria-* attributes.

Included in the accessibility tree

Elements included in the accessibility tree of platform specific accessibility APIs. Elements in the accessibility tree are exposed to assistive technologies, allowing users to interact with the elements in a way that meet the requirements of the individual user.

The general rules for when elements are included in the accessibility tree are defined in the core accessibility API mappings. For native markup languages, such as HTML and SVG, additional rules for when elements are included in the accessibility tree can be found in the HTML accessibility API mappings (working draft) and the SVG accessibility API mappings (working draft).

Note: Users of assistive technologies might still be able to interact with elements that are not included in the accessibility tree. An example of this is a focusable element with an aria-hidden attribute with a value of true. Such an element could still be interacted with using sequential keyboard navigation regardless of the assistive technologies used, even though the element would not be included in the accessibility tree.

Examples for Included in the accessibility tree

Note: The examples presented here are non-normative and not testable. They serve to illustrate some common pitfalls about the definition and to help implementers of ACT rules understand it.

This span element is included in the accessibility tree (by default, elements are included in the accessibility tree).

<span>ACT rules</span>

This span element is not included in the accessibility tree because it is hidden to everybody by the CSS property.

<span style="display:none">ACT rules</span>

This span element is not included in the accessibility tree because it is explicitly removed by the aria-hidden attribute.

<span aria-hidden="true">ACT rules</span>

This span element is positioned off screen, hence is not visible, but is nonetheless included in the accessibility tree.

<span style="position: absolute; top:-9999em">ACT rules</span>

Although the span element with an id of "label" is not itself included in the accessibility tree, it still provides an accessible name to the other span, via the aria-labelledby attribute. Thus, it is still indirectly exposed to users of assistive technologies. Removing an element from the accessibility tree is not enough to remove all accessibility concerns from it since it can still be indirectly exposed.

<span id="label" style="display:none">ACT rules</span>
<span aria-labelledby="label">Accessibility Conformance Testing rules</span>

Although this input element is not included in the accessibility tree, it is still focusable, hence users of assistive technologies can still interact with it by sequential keyboard navigation. This may result in confusing situations for such users (and is in direct violation of the fourth rule of ARIA (working draft)).

<input type="text" aria-hidden="true" name="fname" />

Matching characters

A sequence of characters is considered to match another if, after removing leading and trailing space characters and replacing remaining occurrences of one or more space characters with a single space, the two sequences of characters are equal character-by-character, ignoring any differences in letter casing.

Outcome

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:

  • Inapplicable: No part of the test subject matches the applicability
  • Passed: A test target meets all expectations
  • Failed: A test target does not meet all expectations

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.

Programmatically Determined Link Context

The programmatically determined context of a link (or programmatically determined link context) is the set of all elements that are included in the accessibility tree, and have one of the following relationships to the link:

This definition is based on the WCAG definition of programmatically determined link context.

This definition assumes that the HTML document with the link is a document using HTML according to the specification.

Same resource

Two or more resources can be the same resource even though the URLs for them are different. This can be due to URL parsing, server settings, redirects and DNS aliasing.

If the parsed URLs for two resources are identical, the resources are the same resource.

Depending on the server, URLs can either be case-sensitive or case-insensitive, meaning that <a href="page1.html"> and <a href="Page1.html"> lead to either the same or two different pages.

Fully parsed URLs can be different, but still lead to the same resource after making the HTTP request, due to redirects and DNS aliasing. For example, these URLs are all fully normalized: http://example.com/, http://www.example.com/, https://www.example.com/. The server can however be configured to serve the same site for http and https, and the same site for example.com and www.example.com. This is common, but not guaranteed.

Some types of redirects are also caused by user agents, e.g. ensuring that http://example.com/ and http://example.com resolve to the same resource.

On the other hand, identical relative URLs do not necessarily resolve to the same resource, even if they are in the same web page (HTML). This happen because external content can be included through iframe and URLs in or out of it will resolve relatively to different base URLs.

Semantic Role

The semantic role of an element is determined by the first of these cases that applies:

  1. Conflict If the element is marked as decorative, but the element is included in the accessibility tree; or would be included in the accessibility tree when its hidden state is false, then its semantic role is its implicit role.
  2. Explicit If the element has an explicit role, then its semantic role is its explicit role.
  3. Implicit The semantic role of the element is its implicit role.

Accessibility Support for Definition of Semantic Role for Semantic Role

  • There exist popular web browsers and assistive technologies which do not correctly implement Presentational Roles Conflict Resolution. These technologies will not include in the accessibility tree elements that should be, according to Specifications. Thus, some elements that should have their semantic role fixed by case Conflict above are instead falling into case Explicit and are hidden for users of assistive technologies.
  • A similar conflict exists for focusable elements with a aria-hidden="true" attribute. The WAI ARIA specification does not explain how to solve it. Some browsers give precedence to the element being focusable (and expose it in the accessibility tree) while some give precedence to the aria-hidden attribute (and hide the element).

Web page (HTML)

An HTML web page is the set of all fully active documents which share the same top-level browsing context.

Note: Nesting of browsing context mostly happens with iframe and object. Thus a web page will most of the time be a "top-level" document and all its iframe and object (recursively).

Note: Web pages as defined by WCAG are not restricted to the HTML technology but can also include, e.g., PDF or DOCX documents.

Note: Although web pages as defined here are sets of documents (and do not contain other kind of nodes), one can abusively write that any node is "in a web page" if it is a shadow-including descendant of a document that is part of that web page.


Useful Links


Implementations

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. This section will not be included in the rule when it is published on the W3C website.

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