Image not in the accessibility tree is decorative

  • Rule Type:atomic
  • Rule Id: e88epe
  • Last modified: -
  • Accessibility Requirements Mapping:
    • 1.1.1 Non-text Content (Level: A)
      • Learn More about 1.1.1 (Non-text Content)
      • 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 visible img, svg and canvas elements that are ignored by assistive technologies are decorative

Applicability

Any img, canvas or svg element that is visible and for which one of the following is true:

Exception: This rule never applies to elements for which one of the following is true:

Note: An example of an image ignored because of an ancestor with named from author is when the image is a descendant of a button element that uses aria-label for its accessible name.

Expectation

Each test target is purely decorative.

Note: It is relatively common for an informative image such as an icon to be marked up as decorative, if the text alternative is adjacent to the image. This is a conforming alternative version for the image. This fails the rule but meets conformance requirement 1 of WCAG 2.1.

Assumptions

  • svg elements with a semantic role of graphics-document and with an empty ("") accessible name are ignored by assistive technologies tested for this rule. If some assistive technology does not ignore these elements, and that assistive technology is required for conformance, passing this rule does not ensure all decorative svg elements can be ignored, and the success criterion 1.1.1 Non-text content may still not be satisfied. The same is true for canvas elements with no semantic role and an empty ("") accessible name.
  • A web page with informative images without an accessible name may conform to WCAG 2.1 Level A when the information provided by that image is available elsewhere on the web page itself. For example if an equivalent text is adjacent to the image, or if the text alternative is included in the accessible name of a parent element.

Accessibility Support

No accessibility support issues known.

Background

Test Cases

Passed

Passed Example 1

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This img element with an empty alt attribute which is not included in the accessibility tree is purely decorative.

<p>Happy new year!</p>
<img src="/test-assets/shared/fireworks.jpg" alt="" />

Passed Example 2

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This img element that is ignored by assistive technologies because aria-hidden is set to true is purely decorative.

<p>Happy new year!</p>
<img src="/test-assets/shared/fireworks.jpg" aria-hidden="true" role="img" alt="" />

Passed Example 3

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This img element that is ignored by assistive technologies because it has an explicit semantic role of none is purely decorative.

<p>Happy new year!</p>
<img src="/test-assets/shared/fireworks.jpg" role="none" alt="ignore me" />

Passed Example 4

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This svg element that is ignored by assistive technologies because it has no attribute that would give it an accessible name is purely decorative.

<p>Happy new year!</p>
<svg height="200" xmlns="http://www.w3.org/2000/svg">
	<polygon points="100,10 40,180 190,60 10,60 160,180" fill="yellow" />
</svg>

Passed Example 5

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This canvas element that is ignored by assistive technologies because it has no attribute that would give it an accessible name is purely decorative.

<p>Happy new year!</p>
<canvas id="newyear" width="200" height="200"></canvas>
<script>
	const ctx = document.querySelector('#newyear').getContext('2d')
	ctx.fillStyle = 'yellow'
	ctx.beginPath()
	ctx.moveTo(100, 10)
	ctx.lineTo(40, 180)
	ctx.lineTo(190, 60)
	ctx.lineTo(10, 60)
	ctx.lineTo(160, 180)
	ctx.fill()
</script>

Failed

Failed Example 1

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This img element with an empty ("") alt is not purely decorative.

<img src="/test-assets/shared/w3c-logo.png" alt="" />

Failed Example 2

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This img element which is not included in the accessibility tree because aria-hidden is set to true is not purely decorative.

<img src="/test-assets/shared/w3c-logo.png" aria-hidden="true" alt="W3C logo" />

Failed Example 3

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This img element which is not included in the accessibility tree because it has an explicit semantic role of none is not purely decorative.

<img src="/test-assets/shared/w3c-logo.png" role="none" alt="W3C logo" />

Failed Example 4

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This svg element which has a semantic role of graphics-document and an empty ("") accessible name is not purely decorative.

<p>Best W3C logo:</p>
<svg viewBox="0 0 512 512">
	<path
		d="M108.4 0h23v22.8h21.2V0h23v69h-23V46h-21v23h-23.2M206 23h-20.3V0h63.7v23H229v46h-23M259.5 0h24.1l14.8 24.3L313.2 0h24.1v69h-23V34.8l-16.1 24.8l-16.1-24.8v34.2h-22.6M348.7 0h23v46.2h32.6V69h-55.6"
	/>
	<path fill="#e44d26" d="M107.6 471l-33-370.4h362.8l-33 370.2L255.7 512" />
	<path fill="#f16529" d="M256 480.5V131H404.3L376 447" />
	<path
		fill="#ebebeb"
		d="M142 176.3h114v45.4h-64.2l4.2 46.5h60v45.3H154.4M156.4 336.3H202l3.2 36.3 50.8 13.6v47.4l-93.2-26"
	/>
	<path fill="#fff" d="M369.6 176.3H255.8v45.4h109.6M361.3 268.2H255.8v45.4h56l-5.3 59-50.7 13.6v47.2l93-25.8" />
</svg>

Failed Example 5

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This canvas element which has no semantic role and an empty ("") accessible name is not purely decorative.

<canvas id="w3c" width="200" height="60"></canvas>
<script>
	const ctx = document.querySelector('#w3c').getContext('2d')
	ctx.font = '30px Arial'
	ctx.fillText('ACT Rules!', 20, 40)
</script>

Inapplicable

Inapplicable Example 1

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This img element is included in the accessibility tree because the alt attribute is not empty ("").

<img src="/test-assets/shared/w3c-logo.png" alt="W3C" />

Inapplicable Example 2

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This img element is neither visible nor included in the accessibility tree.

<img src="/test-assets/shared/w3c-logo.png" style="display:none" alt="" />

Inapplicable Example 3

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This img element is not visible because it is positioned off screen.

<style>
	img {
		position: absolute;
		top: -9999em;
	}
</style>
<img src="/test-assets/shared/fireworks.jpg" alt="" />

Inapplicable Example 4

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This svg element is ignored because it is a child of a link that provides its accessible name.

<a href="//example.org" aria-label="SVG star">
	<svg height="200" xmlns="http://www.w3.org/2000/svg">
		<polygon points="100,10 40,180 190,60 10,60 160,180" fill="yellow" />
	</svg>
</a>

Inapplicable Example 5

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This svg element has a semantic role of img and an accessible name from its aria-label attribute.

<svg viewBox="0 0 512 512" role="img" aria-label="HTML 5 logo">
	<path
		d="M108.4 0h23v22.8h21.2V0h23v69h-23V46h-21v23h-23.2M206 23h-20.3V0h63.7v23H229v46h-23M259.5 0h24.1l14.8 24.3L313.2 0h24.1v69h-23V34.8l-16.1 24.8l-16.1-24.8v34.2h-22.6M348.7 0h23v46.2h32.6V69h-55.6"
	/>
	<path fill="#e44d26" d="M107.6 471l-33-370.4h362.8l-33 370.2L255.7 512" />
	<path fill="#f16529" d="M256 480.5V131H404.3L376 447" />
	<path
		fill="#ebebeb"
		d="M142 176.3h114v45.4h-64.2l4.2 46.5h60v45.3H154.4M156.4 336.3H202l3.2 36.3 50.8 13.6v47.4l-93.2-26"
	/>
	<path fill="#fff" d="M369.6 176.3H255.8v45.4h109.6M361.3 268.2H255.8v45.4h56l-5.3 59-50.7 13.6v47.2l93-25.8" />
</svg>

Inapplicable Example 6

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This canvas element is not visible because it is completely transparent.

<canvas width="200" height="200"></canvas>

Inapplicable Example 7

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This canvas element has a semantic role of img and an accessible name from its aria-label attribute.

<canvas id="w3c" width="200" height="60" role="img" aria-label="ACT Rules!"></canvas>
<script>
	const ctx = document.querySelector('#w3c').getContext('2d')
	ctx.font = '30px Arial'
	ctx.fillText('ACT Rules!', 20, 40)
</script>

Inapplicable Example 8

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This img element is visible but included in the accessibility tree.

Note: While it might be better for the PDF icon to be ignored by assistive technologies, because assistive technologies will announce "PDF" twice, the image is not purely decorative. Having assistive technologies ignore it is not required by Success Criterion 1.1.1 Non-text content.

<img src="/test-assets/shared/pdf-icon.png" alt="PDF" /> PDF document

Inapplicable Example 9

Open in a new tab

This is a div element with a background image. Background images must be tested separate from this rule.

<p>Happy new year!</p>
<div
	style="
	width: 260px;
	height: 260px;
	background: url(/test-assets/shared/fireworks.jpg) no-repeat;
"
></div>

Inapplicable Example 10

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This img element has an src attribute which will cause the image request state to be Broken.

<img src="/test-assets/does-not-exist.png" alt="" />

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.

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" />

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.

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).

Visible

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.

Examples for Visible

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

This span element is visible (by default, elements are visible).

<span>Now you can see me!</span>

This span element is not visible because of the CSS visibility property.

<span style="visibility: hidden">I'm the invisible man</span>

This span element is not visible because of the CSS display property.

<span style="display: none">I'm the invisible man</span>

This span element is not visible because it is positioned off-screen

<span style="position: absolute; top: -9999px; left: -9999px;">Incredible how you can</span>

This span element is not visible because it contains only whitespace and line breaks.

<span>
	<br />
	&nbsp;
</span>

This span element is not visible because it has the exact same color as its background.

<span style="color: #00F; background: #00F;">See right through me</span>

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.

No Implementations

Implementation reports are not provided for this rule.

Acknowledgments

assets

  • W3C
  • Wikimedia
  • Adobe
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