While alt text provides a brief description of an image for screen readers, captions and extended descriptions offer all users (not just those with disabilities) the full context, meaning, or interpretation of a visual. This is especially important when the image:
Communicates data (charts, diagrams, infographics)
Conveys symbolism or layered meaning (historical photos, artwork)
Supports comprehension (for neurodivergent or visual learners)
Extended descriptions go beyond alt text and are often placed:
Below the image (caption)
In the surrounding content
In the linked text labeled “Image description” or “Long description”
📌 Prompt:
Please write an image caption and an extended description for the following image. The caption should be 1–2 sentences that summarize the image, and the extended description should provide full context and visual detail for someone who cannot see it. Here’s the image description/context:
[Insert image description or purpose in lesson]
Sample Image Context:
A historical photo used in a U.S. History course showing civil rights marchers crossing the Edmund Pettus Bridge in Selma, Alabama.
AI-Generated Caption:
Civil rights demonstrators march peacefully across the Edmund Pettus Bridge in Selma, Alabama, during the 1965 voting rights movement.
AI-Generated Extended Description:
A black-and-white photograph captures hundreds of civil rights activists walking in tight formation across a steel arch bridge. Many carry signs and wear coats. Police are visible in the distance. The bridge's structure and signage dominate the upper frame, while the determined expressions of the marchers emphasize the gravity of the moment.
Term
Location
Purpose
Needed with Alt Text?
Alt Text
Hidden code behind the image (via image settings or right-click > “Edit alt text”)
Helps screen reader users understand the image
✅ Yes, always
Caption
Directly under the image, visible to all readers
Gives a short explanation or title
Optional but recommended
Extended Description
In the paragraph near the image, in a footnote, or via a link
Gives detailed or instructional info
Only if the image needs deeper context
Use all three when:
The image is critical to understanding the content (e.g., scientific charts, infographics, historic images).
You want to support all learners, including visual learners, ELLs, and students with disabilities.
You're following WCAG guidelines or Universal Design for Learning (UDL) principles.
Scenario: You're inserting an image of students collaborating during a group project.
(Imagine a photo of four college students sitting around a table with laptops, discussing a chart.)
Alt Text (for screen readers):
Four diverse students collaborate with laptops and papers at a table, discussing a printed chart.
Caption (visible under image):
Students work together on a group project in a study lounge.
✅ Use this setup when a brief summary adds value for all readers and the image isn't overly complex.
Scenario: You're inserting an image of students collaborating during a group project.
(Imagine a photo of four college students sitting around a table with laptops, discussing a chart.)
Alt Text (for screen readers):
Four diverse students collaborate with laptops and papers at a table, discussing a printed chart.
Caption (visible under image):
Students work together on a group project in a study lounge.
✅ Use this setup when a brief summary adds value for all readers and the image isn't overly complex.
(Imagine a bar graph comparing enrollment by year for 5 universities.)
Alt Text (for screen readers):
Bar chart showing 10-year enrollment trends for five universities; all show increasing enrollment.
Extended Description (visible in body text or a linked section):
The bar chart illustrates annual enrollment figures from 2013 to 2023 for five Texas universities. Each university shows gradual increases, with the most notable growth seen in University A, which doubled its enrollment. University C had the slowest growth rate but maintained consistent numbers across the decade.
✅ Use this setup when the image content is too complex for alt text alone and needs interpretation or emphasis.
Use all three when:
The image is critical to understanding the content (e.g., scientific charts, infographics, historic images).
You want to support all learners, including visual learners, ELLs, and students with disabilities.
You're following WCAG guidelines or Universal Design for Learning (UDL) principles.
Microsoft Word / PowerPoint
Add alt text, captions, and visible figure labels
office.com
Choose an image you use in class—historical photo, infographic, diagram.
Describe it in a prompt like the one above using ChatGPT or Claude.
Compare the AI-generated caption and extended description with your own.
Ask yourself: Does this support all learners? Would it make sense without the image?
If you're unsure how to test reading order, or encounter issues, contact Instructional Accessibility Designer Terisa O'Dowd for support:
todowd1@twu.edu