Alternative text (alt text) is used to describe the content and function of the images being used. Visually impaired users using screen readers will be read the alt-text so that they can understand an image. Without this alt-text, these users will be unable to get the same information as users without visual impairments. Alternative text is metadata added to an image that does not appear visually, and may differ from the types of language that appears in figure captions.
Best Practices
To be useful, alt text:
- Accurately describes the content of the image
- Is succinct
- Is context sensitive
- Does not refer to the fact that it is describing an image (e.g., do not use alt text which states “image of ….”). When using alt-text, the screen reader will communicate to users that you are referring to an image, so you do not need to specify this again.
Complex images, such as graphs, cartoons, chemical elements, etc., require more detailed descriptions. Please see the Diagram Center Image Description Guidelines for assistance.
Examples
Say you wanted to provide an alt-text for the following image:
Some Good Alt Text Options:
- University of Michigan Law Library
- Law Library at the University of Michigan
Bad Alt Text:
- library.png
- Picture of a library
- Library Michigan Law University
The WebAIM website offers more information on alt text and other examples.