Images add meaning, emotion, and clarity to your content. However, if you don't include alternative text (alt text), some users might miss that message entirely. 

Alt text describes what's in an image and why it's there. Screen readers read alt text aloud, allowing users with visual impairments to understand content just as a sighted user would. 

Including alt text is one of the easiest ways to make your content more accessible, and it supports compliance with digital accessibility requirements. Apps like Word, PowerPoint, Adobe Acrobat, and most website tools have options to include alt text when you add an image. 

Writing effective alt text

  1. Describe the image's purpose, not just its appearance.
    • Think about why the image is being included in your content. For instance, if it's illustrating a concept, describe that concept, not every minor detail.
    • Example: "Student using assistive technology to complete an online quiz," rather than "Student sitting at a desk using a laptop."
  2. Keep it brief and focused.
    • Most alt text should be a short sentence, around 150 characters. If your image contains more complex information–like a chart or an infographic–summarize it and link to or include a longer description elsewhere.
    • Example: "Bar chart showing enrollment growth from 2020 to 2025; see detailed data below."
  3. Skip phrases like "image of" or "picture of"
    • Screen readers announce an image's presence, so there's no need to repeat that information.
  4. Use punctuation and complete thoughts.
    • Proper punctuation helps screen readers pause naturally and improves comprehension.
  5. Match the function.
    • If the image is a button or a link, the alt text should describe the action rather than the visual details of the image.
    • Example: If you're using an icon with a search bar on your site, it's better to say "Search the site" for your alt text, instead of writing what the icon looks like visually such as, "Magnifying glass icon."
  6. Leave decorative images blank.
    • If the image doesn't add meaning and is only used for visual flair, mark it as decorative so screen readers can skip it.
    • Example: a background pattern or a decorative border.

More examples of good alt text

  • Informational photo
    • Alt text example: "Students studying together in the university library."
  • Chart
    • Alt text example: "Pie chart showing 63% of respondents prefer online learning."
  • Logo
    • Alt text example: "University of Iowa logo."
  • Button
    • Alt text example: "Submit application."
  • Decorative
    • Leave blank, but mark item as decorative. 

The W3C's Alt Text Decision Tree can help determine what type of alt text your image needs. 

Common mistakes

  • Writing long, overly detailed descriptions.
  • Leaving out alt text for meaningful images.
  • Adding phrases like "images of" or "photo of."
  • Using alt text to repeat surrounding text instead of enhancing it.
  • Forgetting to describe the function of linked images.

Learn more

Additional resources about alt text can be found on the Web Accessibility Initiative website.