Provide alternative text for visual content
Alternative text (alt text) descriptions are required for all types of visual content, including images, charts, graphs, and other informative non-text (visual) content. Including alt text will help individuals using assistive technology understand the content of images, graphs, and other similar items that may be included in a document, as the alt text will be read aloud when a screen reader encounters an image.
Alt text should succinctly describe the purpose or content of the image in the fewest possible words, ideally fewer than 15. If the image is purely decorative and does not serve an informative purpose, no alt text is necessary. In some cases, such as specific website content editors, you can even mark an image as decorative.
For complex images, including charts, data, infographics, and other similar graphics, there are a few options for adequately describing the image. One option, which would benefit all users, would be to include a thorough description of the complex image in the text of the document, immediately before or after the image. This way, everyone would be able to thoroughly understand the content of the image. If you don't want to add additional content to the document, an alternative would be to add the descriptive content to the document's appendix, and indicate where to find the expanded description.
There are a number of ways to provide alt text, including:
- Use alt text functions in authoring software
- In the text of the document itself
- As a caption below the content
- Use an external resource (such a web link, appendix, or other document)
For more about alt text, see Alternative text for images.