Provides text alternatives for non-text content for user agents and assistive technologies. This allows users who are unable to perceive and / or understand the non-text content to determine its meaning.
Summary
The purpose of this guideline is to ensure that all non-text content is also available in text. Text refers to electronic text, not an image of text. Electronic text has the unique advantage that it is presentation neutral.
Why
Electronic text, such as ASCII or Unicode, can be rendered visually, auditorily, tactilely, or by any combination. As a result, information rendered in electronic text can be presented in whatever form best meets the needs of the user. It can also be easily enlarged, spoken aloud so that it is easier for people with reading disabilities to understand, or rendered in whatever tactile form best meets the needs of a user.
Who it helps
- People who have difficulty perceiving visual content can use assistive technology to read text aloud, present it visually, or convert it to braille.
- Text alternatives may help some people who have difficulty understanding the meaning of photographs, drawings, and other images (e.g., line drawings, graphic designs, paintings, three-dimensional representations), graphs, charts, animations, etc.
- People who are deaf-blind can read the text in braille.
- People who are deaf, are hard of hearing, or who are having trouble understanding audio information for any reason can read the text presentation. Research is ongoing regarding automatic translation of text into sign language.
- Text alternatives support the ability to search for non-text content and to repurpose content in a variety of ways.
- People using mobile devices can turn off images, especially for data-roaming.
- Search engines can index images.
How
Most platforms provide ways of associating alternative text with an image. For example, Web pages, electronic documents like PDF and ePub, and electronic books (ebooks) use HTML and ARIA semantic code to label images, graphics, icons, or buttons with text alternatives. Mobile platforms provide code to associate an image with a text description. Audio and other media with a sound track can provide text transcripts. (Captions for audio are covered in another guideline.)