Alternative (Alt) Text is meant to convey the “why” of the image as it relates to the content of a document or webpage. It is read aloud to users by screen reader software, and it is indexed by search engines. It also displays on the page if the image fails to load, as in this example of a missing image.

The pillars of good alt text

• Write Good Alt Text
• Add alt text all non-decorative images.
• Keep it short and descriptive, like a tweet.
• Don’t include “image of” or “photo of”.
• Leave alt text blank if the image is purely decorative
• It's not necessary to add text in the Title field.