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Digital Accessibility Skills

Learn about how the core digital accessibility skills; headings, links, color contrast, lists, alt text, captions, and tables can help you create more accessible digital content.

Alternative (Alt) Text

“Alternative text, also known as alt text, is descriptive text that conveys the meaning of an image in digital content. It is designed to make visual content accessible to people with vision disabilities.” - Section 508.gov Authoring Meaningful Alternative Text

Whereas a caption typically describes what an image is, alt text describes what an image shows. If an image is purely decorative and serves no other purpose, alt text is usually unnecessary. Though there is technically no limit to how long alt text can be, it is best when it is brief (usually no more than 250 characters, including spaces, though the character limit for some screen readers will be lower than that). [Chicago Manual of Style vol. 18, 3.28]

Tasks where this would be useful in day-to-day workflows may include:

  • Creating and editing webpages/content: Research guides (LibGuides, tutorials, webpages (WordPress, Brightspace, Confluence, etc.)
  • Developing instructional materials: Graphics such as graphs, flow charts, or infographics.
  • Document and presentation creation: Newsletters, slides (PowerPoint, Google Slides, Canva, etc.), scanned and digitized documents
  • Scholarly publishing: Research papers, journal articles, books/book chapters, data tables

Guidelines 

  • Alt text should be as objective as possible and concise. Strive to write alt text around 25-30 words long.
  • Do not repeat descriptions or text already provided in the caption or the surrounding text. When images are completely described by their caption or surrounding text, consider identifying them as decorative images.
  • Spell out all contractions, numbers, and non-Latin letters and present the information in a logical and consistent order.
  • Do not use formatting, such as bullet points, in alt text descriptions.
  • Screen reading software indicates the alt text is a replacement for an image, so do not use redundant phrases such as “Image of...” or “Graphic of...”.
  • Alt text should not contain additional information a sighted person (or someone not using a screen-reader) would miss.

When writing alt text, ask yourself:

  • Why is this visual element here?
  • What information does it present?
  • What is its purpose?
  • If the image were removed, how would I describe it to convey the same information and/or purpose?

Example

broken image icon

Alt text: none

What is wrong with this?

  • Someone using assistive technology such as a screen reader is only going to hear "image" when their technology comes across the content. They'll have no way to know what the image is about, of, includes, etc.

nondescriptive alt text example: 'book club flier"

Alt text: "book club flier"

What is wrong with this?

  • WCAG requires the alt text to "serve the equivalent purpose" as viewing the image. If you are asking your user to infer information from the image, but only providing a title of the image as alt text, that does not provide an equivalent experience as the user won't be able to gather the same information.

Note: Alt text should be brief and that isn't always possible with complex images such as charts or infographics. In those cases, you may need to separate the image into small images and provide alt text for each, or include a long description for the image.

"Book Club, join us 5/17 at 7pm in the Hickory Meeting Room to sign up. All ages welcome."

Alt text: "Book Club, join us 5/17 at 7pm in the Hickory Meeting Room to sign up. All ages welcome."

Why is this better?

  • The user is able to understand the purpose of the image and gain the same insights whether they're using assistive technology or not.

Resources

Here are some general resources that will help you learn more about alt text.

Here are platform specific resources that will help you learn how to use lists within a particular program or software.

The following are criteria from the Web Content Accessibility Guidelines (WCAG) that relate to this skill. Please note that only level A and level AA criteria are listed.