Image and video content can present unique obstacles for some users. Using image and video exclusively, without additional descriptive information, limits how some users receive content. Visually-impaired users may not be able to access the image or video. Users with limited internet access may not be able to load larger image or video files. Providing alternative means of conveying image and video content improves access for all users.
Images
The purpose of alternative text—also referred to “alt text”—is to explain the meaning of an image when someone cannot view the image directly. All visual elements, whether in Microsoft Word, PowerPoint, and Canvas, within a test or email, or elsewhere should include alt text. Extended text descriptions may be necessary for complex images. Typically, alt text contains about 120-125 characters.
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Use image ALT text to quickly describe images for those who cannot see it. Provide alt text that is useful in the context of the document. One tip is to consider what you might relay over the phone when thinking about what alt text to include.
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Consider WHY the image is included. Provide a very brief description if the graphic is simply decorative (e.g., flower), or even skip over purely decorative images. If the graphic is informative, provide a more detailed description. (For example, you might describe an image of a daisy in a horticulture course as Rudbeckia hirta L.)
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ALT text is generally recommended to be concise (about 125 characters).
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For complex images such as a chart, map or other diagram, ALT text can be supplemented by extended text descriptions. Remember to design charts to be understandable in black and white.
The W3C Web Accessibility Initiative has an excellent alt Decision Tree for helping you determine how to use the alt attribute.
Video
Provide alternative resources for multimedia (closed captioning, transcripts, and alternative audio descriptions).
- Provide a text transcript for all audio components. Provide a thorough description of the key visual elements required for comprehension or learning for video components. If the media is audio plus video, provide closed captions, the text transcript, and the video description.
- Use accessible media players. Video files should be embedded or displayed in a player that can be accessed by a screen reader via keyboard commands. Accessible players include QuickTime, RealPlayer, iTunes, and YouTube.
- Accessible media players allow media to be controlled with keyboard shortcuts, meaning that even students who cannot use a mouse can still control playback. You can test for keyboard accessibility in players by pressing the Tab key to navigate to the player, then use the Tab key, Arrow keys, Enter, and Spacebar to interact with the various media players.