Tips on Image Accessibility
How to Write Clear "Alt Text" and Captions for Images and Charts
It is important to offer text-based description for any images and charts you use in your online courses. If the images add meaning to the class, then students are missing out when they can't see the images or when the images don't load.
Tips for Writing Captions:
You've likely encountered a caption before; this is a block of text that appears immediately underneath an image or chart to describe what's in it. To write an effective caption, consider:
- Describe exactly what is in the image or chart. What is a reader looking at? How would you describe what appears in the image or chart? Who created the image and when?
- Keep your description to a sentence or two. Captions needn't be long, and they should focus on the core purpose of the image and who created the image.
Tips for Writing Alt Text:
When you hover your mouse over an image on a website, the little block of text that may appear is called "alt text." Some Internet browsers use screen readers or text-to-speech applications when browsing the Internet; since some users cannot see the images, the alt text is what a screen reader or text-to-speech application will read out loud to help a reader understand what image is appearing on a website. If images do not load properly, alt text is also what will appear in place of the image embedded.
Think of a 50-100 character description of the image. Alt text needs to be short and succinct, as it can be hard for someone using a screen-reader to follow along with and keep track of what is being described in a long description. Prioritize and consider what the most succinct way you can image would be to describe the image or chart. Stick to the essential message of the image or chart. You don't need to state that it's an image.
If you're struggling to describe a complex image, check out WebAIM's Tips for writing alt text.