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Proposed DEPRECATED — Image filename is accessible name for image

Description

This rule checks that image elements that use their source filename as their accessible name do so without loss of information to the user.

Applicability

This rule applies to any HTML element that is included in the accessibility tree and has a non-empty ("") accessible name, for which one of the following is true:

When comparing accessible name and filename, difference in letter casing, leading and trailing whitespace should be ignored.

Expectation

Each test target has an accessible name that serves an equivalent purpose to the non-text content. If there are several image sources, then the accessible name must accurately describe all of them.

Assumptions

This rule assumes that the language of each test target can be correctly determined (either programmatically or by analyzing the content).

Accessibility Support

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

Background

It is fairly common for content management systems (CMS) or other tools to default the alt-text of an image to its filename if no alt-text is provided. However, these names are usually not descriptive (often due to the presence of the file extension). This rule uses this heuristic to pinpoint cases where the accessible name should be looked at by human testers. This rule does not automatically decide in which case a filename is correct (notably, it does not automatically decide whether adding the file extension is acceptable).

Bibliography

Accessibility Requirements Mapping

Input Aspects

The following aspects are required in using this rule.

Test Cases

Passed

Passed Example 1

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This img element has an accessible name equivalent to the filename (ignoring letter casing). The accessible name accurately describes the image.

<html lang="en">
	<img src="/test-assets/image-filename-as-accessible-name-9eb3f6/nyhavn" alt="Nyhavn" />
</html>

Passed Example 2

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This img element has an accessible name equivalent to the filename. Because the image is used in a download link, the presence of the file extension is a relevant part of its description.

<html lang="en">
	<a href="/test-assets/image-filename-as-accessible-name-9eb3f6/nyhavn.jpeg" download
		>Download <img src="/test-assets/image-filename-as-accessible-name-9eb3f6/nyhavn.jpeg" alt="nyhavn.jpeg"
	/></a>
</html>

Passed Example 3

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This image button has an accessible name equivalent to the filename. The accessible name accurately describes the purpose of the button.

<html lang="en">
	<input type="image" src="/test-assets/image-filename-as-accessible-name-9eb3f6/login" alt="login" />
</html>

Passed Example 4

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This img element has an accessible name equivalent to the filename. The accessible name accurately describes the image in the language of the element (French, same as the language of the page).

<html lang="fr">
	<img src="/test-assets/image-filename-as-accessible-name-9eb3f6/pain" alt="pain" />
</html>

Passed Example 5

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This img element has 3 image sources for device-pixel-ratio-based selection, through its src and srcset attributes. Its accessible name is equivalent to the filename of one of its image sources and accurately describes each of them.

<html lang="en">
	<img
		src="/test-assets/image-filename-as-accessible-name-9eb3f6/nyhavn.jpeg"
		srcset="
			/test-assets/image-filename-as-accessible-name-9eb3f6/nyhavn 1.5x,
			/test-assets/image-filename-as-accessible-name-9eb3f6/paris  2x
		"
		alt="Nyhavn"
	/>
</html>

Passed Example 6

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This img element has 3 image sources for Art direction-based selection, through its src attribute and its siblings source elements with the same picture parent. Its accessible name is equivalent to the filename of one of its image sources and accurately describes each of them.

<html lang="en">
	<picture>
		<source media="(min-width: 1000px)" srcset="/test-assets/image-filename-as-accessible-name-9eb3f6/nyhavn" />
		<source media="(min-width: 320px)" srcset="/test-assets/image-filename-as-accessible-name-9eb3f6/paris" />
		<img src="/test-assets/image-filename-as-accessible-name-9eb3f6/nyhavn.jpeg" alt="Nyhavn" />
	</picture>
</html>

Failed

Failed Example 1

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This img element has accessible name matching the image filename (ignoring letter casing). The name does not describe the image.

<html lang="en">
	<img src="/test-assets/image-filename-as-accessible-name-9eb3f6/paris" alt="Paris" />
</html>

Failed Example 2

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This img element has accessible name matching the image filename. The name is just a checksum and does not describe the image.

<html lang="en">
	<img
		src="/test-assets/image-filename-as-accessible-name-9eb3f6/94251e110d24a4c2b6e6ce76e7203374"
		alt="94251e110d24a4c2b6e6ce76e7203374"
	/>
</html>

Failed Example 3

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This img element has accessible name matching the image filename. The presence of the file extension in the accessible name is confusing and results in the accessible name not accurately describing the image.

<html lang="en">
	<img src="/test-assets/image-filename-as-accessible-name-9eb3f6/nyhavn.jpeg" alt="nyhavn.jpeg" />
</html>

Failed Example 4

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This image button has an accessible name matching the filename. The presence of the file extension in the accessible name is confusing and results in the accessible name not accurately describing the image.

<html lang="en">
	<input type="image" src="/test-assets/image-filename-as-accessible-name-9eb3f6/login.png" alt="login.png" />
</html>

Failed Example 5

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This img element has 3 image sources for Art direction-based selection, through its src attribute and its siblings source elements with the same picture parent. Its accessible name is equivalent to the filename of one of its image sources but does not describe the second one (pain).

<html lang="en">
	<picture>
		<source media="(min-width: 1000px)" srcset="/test-assets/image-filename-as-accessible-name-9eb3f6/nyhavn" />
		<source media="(min-width: 320px)" srcset="/test-assets/image-filename-as-accessible-name-9eb3f6/pain" />
		<img src="/test-assets/image-filename-as-accessible-name-9eb3f6/nyhavn.jpeg" alt="Nyhavn" />
	</picture>
</html>

Inapplicable

Inapplicable Example 1

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This img element has a semantic role of presentation, not img.

<html lang="en">
	<img role="presentation" alt="" />
</html>

Inapplicable Example 2

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This img element is not included in the accessibility tree.

<html lang="en">
	<img style="display:none;" alt="" />
</html>

Inapplicable Example 3

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This img element has an accessible name which is not equivalent to the filename.

<html lang="en">
	<img src="/test-assets/image-filename-as-accessible-name-9eb3f6/94251e110d24a4c2b6e6ce76e7203374" alt="Nyhavn" />
</html>

Inapplicable Example 4

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This img element has an accessible name which is not equivalent to the filename because the aria-label value takes precedence over the alt value in the accessible name calculation.

<html lang="en">
	<img
		src="/test-assets/image-filename-as-accessible-name-9eb3f6/94251e110d24a4c2b6e6ce76e7203374"
		alt="94251e110d24a4c2b6e6ce76e7203374"
		aria-label="Nyhavn"
	/>
</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.

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.

Filename

A filename is a text string that identifies an electronically stored file. In a URL it is located at the end of the path, after the last slash and before any query strings. For example the src attribute specifies a URL path of src="/foo/bar.jpg?baz " which contains the filename bar.jpg.

Focusable

An element is focusable if one or both of the following are true:

Exception: Elements that lose focus during a period of up to 1 second after gaining focus, without the user interacting with the page the element is on, are not considered focusable.

Notes:

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:

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:

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:

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

Note: The HTML standard suggests setting the CSS display property to none for elements with the hidden attribute. While not required by HTML, all modern browsers follow this suggestion. Because of this the hidden attribute is not used in this definition. In browsers that use this suggestion, overriding the CSS display property can reveal elements with the hidden attribute.

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:

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

Whitespace

Whitespace are characters that have the Unicode “White_Space” property in the Unicode properties list.

This includes:

Implementations

There are currently no known implementations for this rule. If you would like to contribute an implementation, please read the ACT Implementations page for details.

Changelog

This is the first version of this ACT rule.

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This is an unpublished draft preview that might include content that is not yet approved. The published website is at w3.org/WAI/.