Alt text and image descriptions

Alternative (alt) text and image descriptions are brief written descriptions to describe an image. It explains the “what” of an image, and the “why” — the meaning the image gives to our visual audience.

When reading normal text, screen readers can go slowly, reading each line, word, or even letter. But for picture descriptions, they read the whole thing at once. If the user misses a detail, they have to listen to it all again from the start. Because of this, it’s best to keep picture descriptions short — 150 letters or less. Don’t use extra words like “image” or give too many small details about the picture.

Good alt text for an article about campus and its buildings:
Bascom Hall proudly displaying a bold W banner at the top of Bascom Hill.

Good alt text for an article about the start of the new school year:
Students walking in the grass in front of Bascom Hall on a crisp fall day.

For more information and examples, refer to the Alternative text guide.

Alt text vs. captions

Alt text supports screen readers and is hidden for sighted readers. Use alt text to briefly describe the image to people who use screen readers.

Captions give information about the image to all readers. You can use them to augment your storytelling, share context about the image subjects, and credit the image creator or source.

Long descriptions for complex images

Images like infographics and charts contain a lot of information. These complex images usually need more than 150 characters to describe. In those cases, we recommend creating longer image descriptions instead of alt text. Image descriptions are part of the body copy of a web page or document, giving screen reader users more flexibility. Image descriptions can also benefit all audience members, describing the main takeaways of a complex image.

For more information and examples, refer to the Accessible complex images guide.

• Keep alt text to 150 characters or fewer
• Don’t use extra words like “image of”
• Describe the “why” of the image as well as the “what”
• Describe how the image relates to the major themes or takeaways from the page
• For complex images, add longer image descriptions to the main text of the page