Alternative text is a textual substitute for non-text content in web pages. This article is focused on images, but its principles also apply to multimedia and other non-text content. 

Alternative Text and Captions for Images

Ask Yourself

• Have I described in text what each image does and what each image is?

Recommended Practices

Alternative text serves several functions:

• Screen readers announce alternative text in place of images, helping users with visual or certain cognitive disabilities perceive the content and function of the images.
• Many programs, such a Microsoft and Portable Document Format (PDF) have tools to check for accessibility errors. 
• If an image fails to load or the user has blocked images, the browser will present the alternative text visually in place of the image.
• Search engines use alternative text and factor it into their assessment of the page purpose and content.
• Consider integrating requests for Alt text, captions, and image descriptions into any presenter biography requests. Feel free to adapt the below request for your uses:

  To increase accessibility, we will be adding alternative text, captions, and potentially describing images out loud when giving presentations. These text descriptions of the images help many people including those with low vision to access the images. We want to make sure you’re comfortable with how we describe you. If you would like to describe yourself we will gladly use that description.

Caption text serves several functions:

• A caption refers to a short piece of text placed under/ beside a picture in a social media post, magazine, book, or newspaper that describes that specific picture or explains what is happening in the picture.
• It is a written description or explanation of a photo in order to provide more context.

Resources

• ALT Text Tips Digital Accessibility @Iowa
• Cooper Hewitt Guidelines for Image Descriptions
• WebAIM.org

This Guide was created in partnership with collaborators and supporters across the University of Iowa.
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