Alternative Text
Alternative (Alt) Text is a text description of an image that screen readers (or other assistive technology) can read. Screen readers use alt text to provide information about the image to the reader. Alt text should describe the image and provide context on how it relates to the page content.
Context Clues
As the content expert, it is up to you to determine what alt text is appropriate for your images. You can help make the determination by considering the context of the image. The first question you should ask when writing alternative text for an image is to decide if the image presents content and if the image has a function. It is important to describe the content presented in images. If the image has a function, like acting as a link to a different web page, you’ll want to make sure the alt text is short and sweet (example: “Go to the Assignments page”).
Alt Text Guidelines
- Keep it short, usually 1-2 sentences. Don’t overthink it.
- Consider key elements of why you chose this image, instead of describing every little detail. Present the content and the function of the image.
- No need to say “image of” or “picture of.”
- But, do say if it’s a logo, illustration, painting, or cartoon.
- Don’t duplicate text that’s adjacent in the document or website.
- End the alt text sentence with a period.
- If the image is purely decorative, mark it as decorative.
- Microsoft Word and Ally can both provide suggestions for alternative text that you can revise.
If you have complex images or graphs, include a long description of the information presented in the image somewhere in your document. An easy way to do this is to add a link to the long description below the image, or include it in the page below the image.
Taken from WebAim’s “Alternative Text” article.
Decorative Images
Decorative images do not present important content, are used for layout or non-informative purposes. When analyzing an image, determine whether the image is presenting important content. In many cases you can ask the question “If I could not use this image, what would I put in its place?” to determine appropriate alternative text. If you could get rid of the image with no impact to your work, it may be appropriate to add “decorative image” as the alternative text.