Image has non-empty accessible name

Description

This rule checks that each image either has a non-empty accessible name or is marked up as decorative.

Applicability

This rule applies to HTML img elements and HTML elements that are a semantic img, except if the element is programmatically hidden.

Expectation

Each target element has an accessible name that is not empty (""), or has a semantic role of none or presentation.

Assumptions

There are currently no assumptions.

Accessibility Support

• There is a known combination of a popular browser and assistive technology that does not by default support title as an accessible name.
• There are several popular browsers that do not treat images with empty alt attribute as having a role of presentation but instead add the img element to the accessibility tree with a semantic role of either img or graphic.
• Implementation of Presentational Roles Conflict Resolution varies from one browser or assistive technology to another. Depending on this, some semantic img elements can fail this rule with some technology but users of other technologies would not experience any accessibility issue.
• Images can have their role set to presentation through an empty alt attribute. Presentational Roles Conflict Resolution does not specify what to do if such an image is focusable (it only specifies what to do in case of explicit role="none" or role="presentation"). Some browsers expose these images and some don’t. Thus, this rule may fail for technologies that expose these without creating an accessibility issue for users of other technologies.

Background

Bibliography

• Understanding Success Criterion 1.1.1: Non-text Content
• G94: Providing short text alternative for non-text content that serves the same purpose and presents the same information as the non-text content
• G95: Providing short text alternatives that provide a brief description of the non-text content
• H37: Using alt attributes on img elements
• ARIA6: Using aria-label to provide labels for objects
• ARIA10: Using aria-labelledby to provide a text alternative for non-text content
• H67: Using null alt text and no title attribute on img elements for images that AT should ignore
• F38: Failure of Success Criterion 1.1.1 due to not marking up decorative images in HTML in a way that allows assistive technology to ignore them
• F65: Failure of Success Criterion 1.1.1 due to omitting the alt attribute or text alternative on img elements, area elements, and input elements of type “image”

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 later on level A and higher.
  • 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
• G94: Providing short text alternative for non-text content that serves the same purpose and presents the same information as the non-text content

  • Learn more about technique G94
  • Not required for conformance to any W3C accessibility recommendation.
  • Outcome mapping:
    • Any failed outcomes: technique is not satisfied
    • All passed outcomes: technique needs further testing
    • An inapplicable outcome: technique needs further testing
• G95: Providing short text alternatives that provide a brief description of the non-text content

  • Learn more about technique G95
  • Not required for conformance to any W3C accessibility recommendation.
  • Outcome mapping:
    • Any failed outcomes: technique is not satisfied
    • All passed outcomes: technique needs further testing
    • An inapplicable outcome: technique needs further testing

Input Aspects

The following aspects are required in using this rule.

• Accessibility Tree
• DOM Tree
• CSS Styling

Test Cases

Passed

Passed Example 1

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This img element has an accessible name because of the alt attribute.

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

Passed Example 2

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This semantic img element has an accessible name because of the aria-label attribute.

<div
	role="img"
	aria-label="W3C logo"
	style="width:72px; height:48px; background-image: url(/test-assets/shared/w3c-logo.png)"
></div>

Passed Example 3

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This semantic img element has an accessible name because of an aria-labelledby attribute and an element with matching id.

<div style="display: none" id="img-label">W3C logo</div>
<div
	role="img"
	aria-labelledby="img-label"
	style="width:72px; height:48px; background-image: url(/test-assets/shared/w3c-logo.png)"
></div>

Passed Example 4

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This img element has an accessible name because of a title attribute.

Note: There are assistive technologies that do not support using the title attribute for an accessible name, or in which this feature can be disabled.

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

Passed Example 5

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This img element has an implicit role of presentation because of the empty alt attribute.

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

Passed Example 6

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This img element has an explicit role of presentation because of the value of the role attribute.

<img role="presentation" style="width:72px; height:48px; background-image: url(/test-assets/shared/background.png)" />

Passed Example 7

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This img element has an explicit role of none because of the value of the role attribute.

<img role="none" src="/test-assets/shared/background.png" />

Passed Example 8

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This off screen img element has an implicit role of presentation because of the empty alt attribute.

<div style="margin-left:-9999px;">
	<img alt="" src="/test-assets/shared/background.png" />
</div>

Failed

Failed Example 1

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This img element has an empty accessible name and an implicit role of img because it is missing an alt attribute.

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

Failed Example 2

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This element with role of img has an empty accessible name.

<div role="img" style="width:72px; height:48px; background-image: url(/test-assets/shared/w3c-logo.png)"></div>

Failed Example 3

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This img element inside a div positioned off screen has an empty accessible name and an implicit role of img.

<div style="margin-left:-9999px;"><img src="/test-assets/shared/w3c-logo.png" /></div>

Failed Example 4

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This img element has an empty accessible name because the space in the alt attribute is trimmed off by the accessible name computation. Because of the space, the alt attribute is not empty ("") which gives the element the implicit role of img.

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

Failed Example 5

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This img element has an explicit role of none. However, it is focusable due to the tabindex attribute. Because of this it has a semantic role of img due to Presentational Roles Conflict Resolution. It does not have an accessible name.

<img role="none" tabindex="0" src="/test-assets/shared/w3c-logo.png" />

Inapplicable

Inapplicable Example 1

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This svg element has an implicit role of graphics-document.

<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100">
	<circle cx="50" cy="50" r="40" stroke="green" stroke-width="4" fill="yellow" />
</svg>

Inapplicable Example 2

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This semantic img element is hidden with aria-hidden set to “true”.

<div
	role="img"
	aria-hidden="true"
	style="width:72px; height:48px; background-image: url(/test-assets/shared/w3c-logo.png)"
></div>

Inapplicable Example 3

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This img element is hidden with aria-hidden set to “true”.

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

Inapplicable Example 4

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This img element is hidden because its parent has display: none.

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

Inapplicable Example 5

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This img element is hidden with visibility: hidden.

<div style="visibility: hidden">
	<img src="/test-assets/shared/w3c-logo.png" />
</div>

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.

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.

Focusable

Elements that can become the target of keyboard input as described in the HTML specification of focusable and can be focused.

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).

Included in the accessibility tree

Elements included in the accessibility tree of platform specific accessibility APIs are exposed to assistive technologies. This allows users of assistive technology to access the elements in a way that meets 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.

Programmatically hidden elements are removed from the accessibility tree. However, some browsers will leave focusable elements with an aria-hidden attribute set to true in the accessibility tree. Because they are hidden, these elements are considered not included in the accessibility tree. This may cause confusion for users of assistive technologies because they may still be able to interact with these focusable elements using sequential keyboard navigation, even though the element should not be included in the accessibility tree.

Marked as decorative

An element is marked as decorative if one or more 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 they are programmatically hidden. This is different from marking the element as decorative and does not convey the same intention. Notably, being programmatically hidden 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.

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 http://www.w3.org/2000/svg.

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.

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 Hidden

An HTML element is programmatically hidden if either it has a computed CSS property visibility whose value is not visible; or at least one of the following is true for any of its inclusive ancestors in the flat tree:

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

Note: Contrarily to the other conditions, the visibility CSS property may be reverted by descendants.

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 it is not programmatically hidden, 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.

This definition can be used in expressions such as “semantic button” meaning any element with a semantic role of button.

WAI-ARIA specifications

The WAI ARIA Specifications group both the WAI ARIA W3C Recommendation and ARIA modules, namely:

• Accessible Rich Internet Applications (WAI-ARIA) 1.1
• WAI-ARIA Graphics Module 1.0
• Digital Publishing WAI-ARIA Module 1.0

Note: depending on the type of content being evaluated, part of the specifications might be irrelevant and should be ignored.

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.

Changelog

This is the first version of this ACT rule.