Provide equivalent alternatives to auditory and visual content

These checkpoints are basically about providing text alternatives for images and captions for movies and animations.

If you use anything on your site other than text, for example images, photographs, image maps, video and so on, you must also have a text description that conveys the same information as the object it describes.

The checkpoints are:

• Provide a text equivalent for every image, graphical button, graph or chart, image map region, animation (e.g., animated GIFs), applet and programmatic object, ASCII art, frame, script, audio file and video [Priority 1]
• Provide redundant text links for each active region of a server-side image map [Priority 1]
• Provide an auditory description of the important information of the visual multimedia presentation [Priority 1]
• Provide synchronized equivalent alternatives for any time-based multimedia presentation (e.g., a movie or animation). A synchronised equivalent might be captions or auditory descriptions of the visual track [Priority 1]
• Provide redundant text links for each active region of a client-side image map [Priority 3]

Why the checkpoints are important

Some people with visual impairments and learning disabilities use screen readers that read aloud the text on your site. As screen readers can’t read information in pictures, graphs, charts and photographs, create your text alternative to convey what is important about the image. If you don't create alternative text, a screen reader can't translate the image into synthesized speech or a Braille display so the information is unavailable.

For example:

• If you use images for titles because they look good, blind users can't read the titles and miss a lot of important information
• If you use images for buttons and navigation links, blind users may not be able to navigate the site at all

The use of alternative text, however, isn't just for people who have visual impairments; it benefits everybody. Text-only browsers, mobile phone browsers, and search engines all use alternative text. Remember that many users have old equipment and slow Internet connections via dial-up telephone lines. These users often turn off images to save time and money.

Likewise, audio information is inaccessible to people with hearing impairments, to those who have turned their speakers off when working in an environment where noise may disturb others (e.g., in an office or library), to individuals having difficulty understanding spoken language or accents, and to those using computers with no sound card.

In multi-media presentations, audio content is not accessible to deaf or hard of hearing and videos without descriptions are not accessible to the blind. In both cases, you need to provide a text description. These text alternatives for multi-media are also useful for other reasons. Captions on a video help users who can't hear the audio track because they may be working in a quiet environment, like a library, with the sound turned down or in a noisy environment where the sound is obscured by noise. Ideally, you should synchronise the visual presentation with the auditory track or captions.

Image maps are impossible to use if you don't use a mouse because you need to click on an area of the image to follow the link. You might not use a mouse if you work on a laptop, a mobile device, or a screen reader. Some users may also not use a mouse if they have limited manual dexterity and can't control it accurately.