Alternative Text
Alternative text (alt text) is a written alternative to an image. It’s a short description that can be read aloud by screen readers for users with visual impairments. It is necessary for any simple visual items, such as photos, graphs, charts, illustrations, and even memes.
Note that if an image is complex, alt text is insufficient, and a long description or another alternative may be needed in addition to alt text. Complex images include detailed graphs and charts, maps, music scores, diagrams, equations, and other STEM content.
Audio Description
Audio description is like alternative text for video. It’s a narrative explanation of visual or nonverbal information. This is essential for people with visual impairments who may otherwise miss out on important information.
Color Contrast
Color contrast is about how one color stands out from another color. It’s especially important to consider the color difference between text and the background, and between sections depicting meaning, such as pie charts and maps.
Descriptive Links
Links, or URLs, should tell the user exactly where they’ll go if they click on them. They should make sense when taken out of the context of the surrounding text. If the link text is not descriptive, it will be unclear or difficult to read where the links lead.
Headings
Headings provide extra information about the structure of the document at the code level. They are used to create an outline, or table of contents, that helps users navigate the content more efficiently. Various assistive technologies can tap into the heading structure to make sense out of the document.
Long Description
When images are complex, simple alternative text is not enough. This is especially common in instructional content that students are expected to learn from, such as diagrams, charts, and graphs. In these cases, long description details everything the audience is expected to get out of the image.
MathML
MathML is a way of coding equations so they display correctly on a screen and are also navigable with assistive technology such as screen readers and text-to-speech software.
Transcripts
Transcripts provide an accurate text version of audio content, either for video or audio files. They’re usually a downloadable document, most commonly in Word format.
Captions
Captions, also called subtitles, provide a visual alternative to audio information. The caption text is displayed below the video so you can see the video synchronized with the text.