Accessibility FAST
Alternative Text
Quick Start Guide
To get started with alt text:
Describe informative images
Alt text is a description that is read by screen reader software to blind and low-vision users. Write a brief description of the image if it contains information.
Mark decorative images
Alt text depends on context and purpose. Images included for purely aesthetic purposes, or that have an adjacent text equivalent, may be marked as decorative.
If unsure, err on the side of adding alt text. It is better to present information twice than have someone miss out completely.
Use type + focus + details
To write alt text: Include the type of visual, describe the focus, and add essential details. Consider how you would describe the image if talking to a friend on the phone. Use proper punctuation and grammar and limit alt text to 2 or 3 brief sentences.
Example
[type] Diagram of [focus] satellite image resolutions comparing real object shape to satellite images taken at 30m, 10m, and 1m resolution images. [details] The diagram illustrates that the shape of an object will be more accurately represented as the resolution of a satellite image increases.
Alt text, caption, description
Depending on the complexity of the image it is important to know when to use alt text, a figure caption, or long description. Alt text is only read to screen reader users, figure captions are a text description (usually) below an image, and a long description is a text equivalent in adjacent text or linked in the figure caption.
Use AI as a starting point
AI has rapidly improved in describing images, particularly the structure of complex images and extracting text from images. Edit AI generated descriptions for accuracy and clarity. Read more about using AI to generate alt text.
Moving forward…
Understand that alternative text is so fundamental to accessibility it is the first Web Content Accessibility Guideline (1.1.1). Writing alt text is somewhat of an art. Remember to try your best, ask for help, and try to be as inclusive as possible.
For more information on Alt Text, move to the next page.
