Links with identical accessible names have equivalent purpose

  • Rule Type:atomic
  • Rule Id: b20e66
  • Last modified: Nov 02, 2020
  • Accessibility Requirements Mapping:
    • 2.4.9 Link Purpose (Link Only) (Level AAA)
      • Learn More about 2.4.9 Link Purpose (Link Only)
      • Required for conformance to WCAG 2.0 and later on level AAA.
      • 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 resolve to the same resource or equivalent resources.

Applicability

This rule applies to any set of any 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.

Expectation

When followed, the links in each set of target elements resolve to the same resource or to equivalent resources. 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 would not be ambiguous to users in general when seen in context on the web page, which is the exception mentioned in Success Criterion 2.4.9 Link Purpose (Link Only). If the links are ambiguous to users in general, users of assistive technologies are not at a disadvantage when viewing the links out of context, e.g. on a list of links in a screen reader, 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.

Accessibility Support

  • 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 but resolve to different resources without failing Success Criterion 2.4.9 Link Purpose (Link Only) (if said links are in separate documents or shadow trees).
  • Implementation of Presentational Roles Conflict Resolution varies from one browser or assistive technology to another. Depending on this, some elements can have a semantic role of link and fail this rule with some technology but users of other technologies would not experience any accessibility issue.

Background

Test Cases

Passed

Passed Example 1

Open in a new tab

A set of two HTML a elements have the same accessible name and link to the same resource.

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

Passed Example 2

Open in a new tab

These two HTML a elements resolve to the same resource after instant redirect. The redirect means that the URLs look different but load the same page.

<html lang="en">
	<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html">Contact us</a>
	<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/redirect.html">Contact us</a>
</html>

Passed Example 3

Open in a new tab

These two links resolve to resources that are not the same (different URLs), but the resources are completely identical, in this case the contact details being the same in two locations, thus serving the same purpose.

<html lang="en">
	<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html">Contact us</a>
	<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index-copy.html">Contact us</a>
</html>

Passed Example 4

Open in a new tab

These two links go to pages where the content section is the same, but where the navigation options (bread crumbs and local sub menus) differ due to different placement in navigation hierarchy. In the example, the contact details are the same format but in different locations.

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

Passed Example 5

Open in a new tab

These two HTML a elements link to URLs that differ due to trailing slashes, but resolve to the same resource after redirects caused by user agent. The redirect means the URLs look different but load the same page.

<html lang="en">
	<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/">Contact us</a>
	<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66">Contact us</a>
</html>

Passed Example 6

Open in a new tab

These two links go to pages that contain different amounts of information and/or differently worded information, but fulfill the same purpose in relation to the link. In the example, the phone number is in the same format but in different locations.

<html lang="en">
	<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page1.html">Call us</a>
	<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page2.html">Call us</a>
</html>

Passed Example 7

Open in a new tab

These two links go to pages that have the same advertised key content but use different layouts. In the example, the contact details are the same format but in different locations.

<html lang="en">
	<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page1.html">Contact us</a>
	<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page3.html">Contact us</a>
</html>

Passed Example 8

Open in a new tab

These two HTML span element have an explicit role of link, and lead to the same resource. This example is showing ARIA markup for a link compared to the other HTML examples.

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

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

Passed Example 9

Open in a new tab

These two SVG a elements have the same accessible name and link to the same resource. The example is one SVG area but with 2 formats of links. One uses an image and the other uses text.

<html lang="en">
	<svg viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
		<a href="https://act-rules.github.io/" aria-label="ACT rules">
			<circle cx="50" cy="40" r="35" />
		</a>

		<a href="https://act-rules.github.io/">
			<text x="50" y="90" text-anchor="middle">
				ACT rules
			</text>
		</a>
	</svg>
</html>

Passed Example 10

Open in a new tab

A set of one SVG a element and one HTML a element that have the same accessible name and link to the same resource.

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

<svg viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
	<a href="https://act-rules.github.io/" aria-label="ACT rules">
		<circle cx="50" cy="40" r="35" />
	</a>
</svg>

Passed Example 11

Open in a new tab

All three links have the same accessible name. The second link ("from the light") is only part of the light tree. When the shadow tree is attached to host and flattened, this link is overwritten and therefore not part of the flat tree (and thus not rendered). Hence, only the first and third link are considered by this rule and they both point to the same resource.

<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/about/contact.html">Contact us</a>
all the time.

<div id="host">
	<span
		><a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/admissions/contact.html"
			>Contact us</a
		>
		from the light.</span
	>
</div>

<script>
	const host = document.getElementById('host')
	const shadowRoot = host.attachShadow({ mode: 'open' })

	shadowRoot.innerHTML =
		'<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/about/contact.html">Contact us</a> from the shadow.'
</script>

Passed Example 12

Open in a new tab

The browsing context of the iframe has the browsing context of the main document as an ancestor browsing context. Hence, they share the same top-level browsing context (namely, the browsing context of the main document) and are part of the same web page (HTML). Therefore, both links are considered and, since they refer to the same document, the rule passes.

<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/about/contact.html">Contact us</a>
from the top level.

<iframe
	srcdoc="<a href='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/about/contact.html'>Contact us</a> from the iframe"
></iframe>

Failed

Failed Example 1

Open in a new tab

These two links have the same accessible name but go to different resources. They open completely different pages.

<html lang="en">
	<a href="https://act-rules.github.io/">ACT rules</a>
	<a href="https://www.w3.org/community/act-r/">ACT rules</a>
</html>

Failed Example 2

Open in a new tab

The same accessible name is used for two links going to web pages that are similar, but have different information in their content. The example given contains different contact details for each page. They have a similar purpose but do not match.

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

Failed Example 3

Open in a new tab

These two HTML span elements have an explicit role of link, but lead to resources that offer different content. The example given contains different contact details for each page. They have a similar purpose but do not match.

<html lang="en">
	<span
		role="link"
		tabindex="0"
		onclick="location='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/about/contact.html'"
	>
		Link text
	</span>

	<span
		role="link"
		tabindex="0"
		onclick="location='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/admissions/contact.html'"
	>
		Link text
	</span>
</html>

Failed Example 4

Open in a new tab

The same accessible name is used for image links going to different resources. They open completely different pages.

<html lang="en">
	<a href="https://act-rules.github.io/"><img src="/test-assets/shared/act-logo.png" alt="ACT rules"/></a>
	<a href="https://www.w3.org/community/act-r/"><img src="/test-assets/shared/act-logo.png" alt="ACT rules"/></a>
</html>

Failed Example 5

Open in a new tab

These two SVG a elements have the same accessible name but link to different resources. They open completely different pages.

<html lang="en">
	<svg viewBox="0 0 100 100" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
		<a href="https://act-rules.github.io/" aria-label="ACT rules">
			<circle cx="50" cy="40" r="35" />
		</a>

		<a href="https://www.w3.org/community/act-r/">
			<text x="50" y="90" text-anchor="middle">
				ACT rules
			</text>
		</a>
	</svg>
</html>

Failed Example 6

Open in a new tab

These two links resolve to same resource after redirect, but the redirect is not instant. The user will notice the redirect due to a pause.

<html lang="en">
	<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/index.html">Contact us</a>
	<a href="/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/redirect1.html">Contact us</a>
</html>

Inapplicable

Inapplicable Example 1

Open in a new tab

These a and area elements have no href attribute. Thus they are not links and 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 links have different accessible names. The rule only applies to identical accessible names, not to identical link destinations.

Note: It is a best practice for Success Criterion 2.4.9: Link Purpose (Link Only) that identical links have identical accessible names. This is however not a requirement.

<html lang="en">
	<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>
</html>

Inapplicable Example 3

Open in a new tab

These span elements do not have a semantic role of link. They are not valid links.

<html lang="en">
	<span onclick="location='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page1.html'">
		Contact Us
	</span>

	<span onclick="location='/test-assets/links-with-identical-names-serve-equivalent-purpose-b20e66/page2.html'">
		Contact Us
	</span>
</html>

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).

For more details, see examples of accessible name.

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 ("").
  • The accessible name and description computation suggest that if an aria-labelledby attribute refers to an existing but empty element, the computation should stop and return an empty name without defaulting to the next steps. Several user agents and assistive technologies chose to use the next step in the computation in this case.

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.

Hidden State

An HTML element's hidden state is "true" if at least one of the following is true for itself or any of its ancestors in the flat tree:

  • has a hidden attribute; or
  • has a computed CSS property display of none; or
  • has a computed CSS property visibility of hidden; or
  • has an aria-hidden attribute set to true

In any other case, the element's hidden state is "false".

Implicit Semantic Role

The implicit semantic role of an element is a pre-defined value given by the host language which depends on the element and its ancestors.

Implicit roles for HTML and SVG, are documented in the HTML accessibility API mappings (working draft) and the SVG accessibility API mappings (working draft).

Accessibility Support for Implicit Semantic Role

  • Images with an empty alt attribute should have an implicit role of presentation, according to the HTML Accessibility API Mapping (work in progress). However, there are several popular browsers that do not treat images with empty alt attribute as having a role of presentation. Instead, they add the img element to the accessibility tree with a role of either img or graphic.

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).

For more details, see examples of included in the accessibility tree.

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 using sequential keyboard navigation regardless of the assistive technologies used, even though the element would not be included in the accessibility tree.

Marked as decorative

An element is marked as decorative if one of the following conditions is true:

  • it has an explicit role of none or presentation; or
  • it is an img element with an alt attribute whose value is the empty string (alt=""), and with no explicit role.

Elements are marked as decorative as a way to convey the intention of the author that they are pure decoration. It is different from the element actually being pure decoration as authors may make mistakes. It is different from the element being effectively ignored by assistive technologies as rules such as presentational roles conflict resolution may overwrite this intention.

Elements can also be ignored by assistive technologies if their hidden state is true. This is different from marking the element as decorative and does not convey the same intention. Notably, the hidden state of an element may change as users interact with the page (showing and hiding elements) while being marked as decorative should stay the same through all states of the page.

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.

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.

ToolConsistencyCompleteReport
axe-coreconsistentYesView Report
QualWebconsistentYesView Report
Alfapartially-consistentYesView Report

Acknowledgments

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