Change Proposal: Location of alt text guidance


Remove from the HTML specification section Requirements for providing text to act as an alternative for images, and the deliverable HTML5: Techniques for providing useful text alternatives and request that these collectively become a deliverable of the Web Content Accessibility Guidelines Working Group.


The HTML 5 specification currently has two sets of advice about providing useful text alternatives. One is Requirements for providing text to act as an alternative for images, the other is a separate closely related document HTML5: Techniques for providing useful text alternatives.

A subjective summary of the genesis of these resources is that the HTML 5 draft long ago made the alt attribute an optional feature of the img element, because use cases could be presented for which a good value was unknown. Accessibility advocates objected that this renders the img element incomplete from a non-visual browsing perspective and deprioritizes accessibility in the HTML 5 conformance model. To partially address that concern while retaining a deterministic conformance model, content was introduced into the specification that detailed circumstances in which the alt attribute is required or particular values are valid; this is the section embedded in the specification referenced above. Accessibility advocates, however, believed this did not adequately address the initial concern and did not present advice that uniformly and completely represents accessibility best practices. They attempted to improve this section through a detailed Change Proposal, but ultimately the difficulty in gaining traction on that in the specification led to the spinning off of the change proposal as a separate deliverable of the HTML Working Group, which is the second resource referenced above.

There are a number of unresolved issues related to the above history, and also a lot of good work that has been done. The perspective driving this Change Proposal is that the requirements and use cases driving the history up to now remain unmet, while new problems have been introduced:

  1. The two resources overlap and potentially contradict.
  2. The advice is overly prescriptive for a content language specification.
  3. The advice constitutes "best practices" guidelines that is applicable to a wider range of content technologies than HTML.

Problem 1 seems self-evident, and the remainder of this rationale focuses on problems 2 and 3.

W3C produces a variety of materials that play different roles. Two roles that are often confounded are content language definitions, and authoring best practice recommendations or guidelines. A content language specification defines the features of a content language, its lexical form, and processing expectations, while authoring guidelines suggest how best to take advantage of the content language features to achieve particular goals. There is a tendency to develop the two together, since content language features need to meet the use cases that drive authoring guidelines. Structually, however, the two types of document should be kept separate. When one specification includes both kinds of information, it becomes difficult to tell what statements are in which category and introduces confusion into the normative model. Small authoring suggestions are useful to help explain the intent or use of a content language feature, but these need to be clearly non-normative, offered as guidance only, and not allowed to grow into a full set of best practices within the content language specification itself.

In general, the HTML 5 specification observes this principle and focuses on defining the features of the HTML 5 language without overly prescribing authoring or user agent expectations. But the section on text alternatives is a notable exception. The confusion it introduces on what constitutes a normative part of the HTML 5 conformance model is a part of the problem that has led to difficulty agreeing on the appropriate content of that section. Separating it would allow a clean conformance model for HTML 5 and allow accessibility authoring practices to be maintained in a forum more focused on that. Note that separating this content does not relieve HTML 5 of the responsibility to provide the features necessary to author accessible content, it merely deconfounds the HTML 5 conformance model from the accessibility practices.

Beyond the issue of confounding technical features with authoring practices, in this particular case the authoring practices are applicable to more content languages than HTML. The guidance for optimal text alternatives in the various contexts for images applies to any content language that provides images with support for text alternatives. If each content language were to define its own authoring practices, there would be both repetition of substantially similar information, and high risk that recommendations for similar situations would be different across different content languages. This would introduce confusion to authors and likely reduce the quality of text alternatives overall across the Web. For this reason, it is preferrable to provide the resource in a location where it can be referenced by all content languages for which it is applicable. Because the section referenced above relates to accessibility authoring practices for text alternatives, a resource produced by the Web Content Accessibility Guidelines seems to be the most appropriate location. This group has produced the W3C's technology-neutral accessibility authoring advice and maintains support materials including general techniques, technology-specific techniques, and interpretive guidance, so is well suited to maintain this document.


  1. Remove from the HTML specification the section Requirements for providing text to act as an alternative for images.
  2. In the HTML specification 4.8.1 The img element, change the sentence "The requirements on the alt attribute's value are described in the next section." to "Recommendations for optimal values of the alt attribute are available in external resources, such as [Techniques for providing useful text alternatives]".
  3. Remove HTML5: Techniques for providing useful text alternatives from the set of deliverables of the HTML Working Group.
  4. Request the WCAG Working Group take over development of HTML5: Techniques for providing useful text alternatives. The possibility of this has been raised with the WCAG Working Group and it is expected that the group will accept the deliverable.


Positive Effects

Negative Effects

Conformance Classes Changes

Conformance checkers that focus on HTML 5 conformance would need to remove checks related to the removed content.

Authoring tools may need to remove advice about conformance implications of providing certain kinds of text alternatives.


Existing implementations of the heuristics in this section may not be removed, resulting in contradictory guidance from various tools on conformance when using the img element.


References are provided inline.