Re: Request for PFWG WAI review of Omitting alt Attribute for Critical Content


PFWG has been asked for input on an issue

Request for PFWG WAI review of Omitting alt Attribute for Critical  

With the advice of numerous commentors on the wai-xtech mailing list

(see for example:)

The PFWG has reached consensus on the following discussion.

We would be glad to discuss this with you further if you have questions.

/chair, PFWG


The current TR draft for HTML5 contains the following language:

A key part of the content that doesn't have an obvious textual  

In certain rare cases, the image is simply a critical part of the  
content, and there might even be no alternative text available. This  
could be the case, for instance, in a photo gallery, where a user has  
uploaded 3000 photos from a vacation trip, without providing any  
descriptions of the images. The images are the whole point of the  
pages containing them.

In such cases, the alt attribute may be omitted, but the alt  
attribute should be included, with a useful value, if at all  
possible. If an image is a key part of the content, the alt attribute  
must not be specified with an empty value.



1.  By the principles, HTML5 wants to support accessibility

2.  By their charters, WAI groups (here WCAG) are the go-to
experts in matters of accessibility

3.  WCAG requires @alt (WCAG1) or the function that in HTML4
is provided by @alt (WCAG2)  [editorial note -- add links]

4.  By the principles, if it ain't broke, don't fix it.

5.  Conclusion:  barring the introduction of new, good
reasons for a change, the failure of the HTML5 draft to make
@alt on <img> an across-the-board requirement (even if sometimes
it has the value of &quot;&quot;) is a bug.



The applicable provision in the WCAG 1.0 Recommendation is Checkpoint  


Provide a text equivalent for every non-text element (e.g., via
"alt", "longdesc", or in element content). This includes: images,
graphical representations of text (including symbols), image map
regions, animations (e.g., animated GIFs), applets and programmatic
objects, ascii art, frames, scripts, images used as list bullets,
spacers, graphical buttons, sounds (played with or without user
interaction), stand-alone audio files, audio tracks of video, and
video. [Priority 1]

and in the WCAG 2.0 Last Call draft it is stated thus:


1.1.1 Non-text Content: All non-text content has a text alternative  
that presents equivalent information, except for the situations  
listed below. (Level A) How to Meet 1.1.1 Understanding 1.1.1

Controls, Input: If it is a control or accepts user input, then it  
has a name that describes its purpose. (See also Guideline 4.1.)

Media, Test, Sensory: If it is (1) synchronized media, (2) live audio- 
only or live video-only content, (3) a test or exercise that must be  
presented in non-text format, (4) primarily intended to create a  
specific sensory experience, then text alternatives at least provide  
descriptive identification of the non-text content , or (5) a media  
alternative to text that is clearly labeled as such . (For  
synchronized media, see also Guideline 1.2.)

Note: Prerecorded audio-only and video-only files would be covered  
under Success Criterion 1.1.1, which requires text alternatives that  
present equivalent information.

CAPTCHA: If it is to confirm that content is being accessed by a  
person rather than a computer, then text alternatives that identify  
and describe the purpose of the non-text content are provided, and  
alternative forms of CAPTCHA using output modes for different types  
of sensory perception are provided to accommodate different  

Decoration, Formatting, Invisible: If it is pure decoration, or used  
only for visual formatting, or if it is not presented to users, then  
it is implemented in a way that it can be ignored by assistive  



The language "In such cases, the alt attribute may be omitted," gives  
appearance of creating a policy line that is inconsistent with WCAG,
whether 1.0 or 2.0. As such, this needs to be changed. HTML WG should
re-work the <img> element section to bring it into line as techniques
for implementing WCAG 2.0. We say 2.0 because of the strong
likelihood that WCAG 2.0 will precede HTML5 to Recommendation status.

WCAG WG is chartered to set Accessibility guidelines and HTML
WG is not; so HTML5 should be careful to create features that support
WCAG and describe their use in ways that conform to WCAG.


/self (chair hat off)

Received on Wednesday, 6 February 2008 18:13:38 UTC