Guideline for Alternative Text

These apply to all authoring softwares (e.g., Word, Sheets, Mailchimp, InDesign, Canva, etc.) and mediums (web, document, email, etc.).

  • Use descriptive text for links.
  • Provide alternative text (alt text) for any image that has a function or conveys meaning.
    • Keep alt text to fewer than 250 characters–ideally, it should be fewer than 125 characters (roughly 25 words).
    • Avoid text in images. If unavoidable, use the same text in the alt text.
    • Use correct grammar and punctuation in alt text. (Screen readers rely on punctuation to provide conversation-like breaks.)
  • Removing images (a “text only” format) makes the information less accessible for users with cognitive and learning disabilities. Don’t use this as a solution to accessibility checker errors.

Guidance for specific image types

Decorative images that do not add information:

  • Photos and other images can be either decorative or informational (see below). 
  • In documents, mark as decorative or as an artifact.
  • On web pages, tag as null (alt=””).

Icons (e.g., a phone or fax icon) used to label other information:

  • Alt text should identify the information conveyed by the icon.
    • Example: “STARRS phone number” rather than “image of a phone”).

Logos

  • Are considered essential information in many placements–provide alt text.
    • A logo in a footer or margin carried across multiple pages would be decorative.

Photos, nondecorative

  • Original photos: Alt text should include information on the context and subject.
    • Example: Alt text for a photo of Summer Institute attendees might be, “The 2025 Summer Institute class gathers outside the Perry Building.”
  • Stock photos: If a stock photo is meant to convey an impression, it is not decorative.
    • Example: The alt text for a stock photo of a cat on a veterinarian’s website could read, “Dr. Doolittle specializes in feline health.” 

Linked images 

  • Alt text should describe the destination.
    • Example: Alt text for a button that says “Register” should read “Summer Institute registration page.” 

Complex images

  • Examples include flow charts, data graphs, maps, and illustrations that require the user to understand the image.
  • Context matters! Sometimes a complex image is meant to convey a feeling or concept rather than the information included in it, and the alt text should reflect intent rather than content.
    • Example: Alt text for a presentation poster not intended to be read by sighted users could read “Althea Ramirez’s recent poster covers Topics A, B, C, and D” instead of a verbatim copy of the poster’s content.
  • Use accompanying text to summarize more complex images. 
  • On the web, there is an option for linking a complex image to a “long description.” 
  • Alt text for data graphs should include the essential information the graph is trying to convey. For example, “The graph shows that deaths peaked in May then fell over the next six months.”
  • Alt text could also include information on where to find the supporting data table if available. 
  • Simplifying complex images would make them more accessible to everyone, including those with low vision and learning disabilities. 

Learn more

Web Accessibility Initiative’s (W3C) alt text decision tree (applicable for documents as well) 

W3C’s detailed tutorial on images (mostly useful for web, but also helpful for documents) 

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