From HTML WG Wiki
Action 54: Second Draft
- Issue 31: missing-alt, Raised on behalf of Laura Carlson
- Action 54: Work with SteveF draft text for HTML 5 spec to require producers/authors to include @alt on img elements
Statement of Purpose
The following second draft text is based on the February 6, 2008 PFWG finding that the HTMLWG:
"...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."
The aim of this draft is therefore to comply with WCAG 2.0, Guideline 1.1. Text Alternatives:
"Provide text alternatives for any non-text content so that it can be changed into other forms people need, such as large print, braille, speech, symbols or simpler language..."
Additional advice has been sought, is needed, and is pending from PFWG for this action item regarding the following:
- Use of normative language in a general sense
- Adopting the WCAG 2.0 definition of "text alternative" and related explanatory documentation, in order to support conformance to WCAG 2.0
- Removal or modification of the "Rorschach inkblot test" example
- Removal of "An image in an e-mail or document intended ..."
Second Draft Text for the HTML 5 Specification
Note: The remainder of the authoring section of 3.14.2 is informative.
Text alternatives are a primary way for making information accessible, because they can be rendered through any sensory modality (for example, visual, auditory or tactile) to match the needs of the user. Providing text alternatives allows the information to be rendered in a variety of ways by a variety of user agents. For example, a person who cannot see a picture can have the text alternative read aloud using synthesized speech.
The value requirements for the alt attribute is dependent on the function of an image in the context of the document. To determine appropriate Text alternatives it is important to think about why an image is being included in a document. What is its purpose? Thinking like this will help you to understand what is important about the image for the page's intended audience. Every image has a reason for being on a page because it either provides useful information, performs a function, or enhances aesthetics. Therefore, knowing what the image is for, makes writing appropriate Text alternatives easier.
General alt Text Best Practices
- Provide the same informational content as the image.
- Where an image performs a specific function, such as a graphical link, provide information about its functionality.
- Be succinct as possible while still conveying equivalent values. Short text that describes its purpose or gives an overview will often suffice.
- Write suitable alt text according to context. The same image in a different situation may need very different alt text.
- Avoid redundant alt text. An example of this would be repeating the same text in your document, as well as in the alt attribute, and is unnecessary.
General alt Text Example
A candid photograph of a dog digging in the sand on the beach.
<img src="dog.jpg" alt="A dog digging in the sand on the beach">
For specific authoring techniques follow Techniques for WCAG 2.0.
Note: Usage examples and code samples from the Action 54 first draft are being refined and and most have already been submitted as Techniques for WCAG 2.0. If they are accepted, this document will link to them there. A format specification is not a tutorial. Including detailed guidance in ALT attribute techniques could be seen as usurping the role of WCAG 2.0 and its techniques documents. As PF has said, "WCAG WG is chartered to set Accessibility guidelines and HTML WG is not".
Use cases include but are not limited to:
- Purely Decorative Images
- Box corners
- Complex Data Images
- Other Complex Images
- Images of Text
- ASCII Art
- CAPTCHA Images
- Obscured images of textual characters
- Obscured image of words
- Images of Symbols
- Functional Images
- Navigation Links
User Agent Requirements
Advice has been sought, is needed, and is pending from PFWG regarding the separate issue of what an authoring or publishing tool should insert, in a case where no alt has been provided by the author, but the image is known to be "critical content".
ATAG 1.0 Techniques
- Prompt the author to provide equivalent alternative information W3C World Wide Web Consortium Note.
- Check for and inform the author of accessibility problems. W3C World Wide Web Consortium Note.
- Assist authors in correcting accessibility problems. W3C World Wide Web Consortium Note.
- Provide the author with a summary of the document's accessibility status. W3C World Wide Web Consortium Note.
- If markup produced by the tool does not conform to W3C specifications, inform the author. W3C World Wide Web Consortium Note.
- Do not automatically generate equivalent alternatives. Do not reuse previously authored alternatives without author confirmation, except when the function is known with certainty W3C World Wide Web Consortium Note.
- Ensure that when the tool automatically generates markup it conforms to the W3C's Web Content Accessibility Guidelines 1.0 W3C World Wide Web Consortium Note.
ATAG 2.0 Techniques
- Prompt authors to create accessible content. W3C World Wide Web Consortium Note.
- Assist authors in checking for accessibility problems. W3C World Wide Web Consortium Note.
- Assist authors in repairing accessibility problems. W3C World Wide Web Consortium Note.
- Assist authors to manage, edit, and reuse equivalent alternatives for non-text objects. W3C World Wide Web Consortium Note.
- Assist authors with accessible templates and other pre-authored content. W3C World Wide Web Consortium Note.
- Ensure that automatically generated content is accessible. W3C World Wide Web Consortium Note.
- Ensure that accessible authoring actions are given prominence. W3C World Wide Web Consortium Note.
- Ensure that features of the authoring tool supporting the production of accessible content are available. W3C World Wide Web Consortium Note.
UAAG 1.0 Techniques
- Render conditional content W3C World Wide Web Consortium Note.
- Repair missing content W3C World Wide Web Consortium Note.
- Programmatic access to non-HTML/XML content W3C World Wide Web Consortium Note.
This document is authored and offered to the HTML WG by working group members:
- Steven Faulkner
- Joshue O Connor
- Laura Carlson
Peer reviewed by:
- Gez Lemon
- Gregory J. Rosmaita
May 28, 2008.