Include alternative text (alt text) to appropriately describe the content and/or function of all images.
Alt text allows screen reader users to hear a description of the content and function of your image.
Images that are purely decorative should include blank alt text. Leaving alt text blank tells screen readers to skip over the image.
If an image is used as a link or for another function, the alt text should describe that function or link destination.
Avoid redundancy. If the same information is already presented as text within the context of the image then leaving alt text blank may be most appropriate.
Avoid verbose alt text. Alt text should typically only need to be a few words. Sometimes longer alt text will be appropriate but if you need to write more than a sentence consider presenting that information on the page itself rather than relying on an image.
Avoid using images of text. Where an image of text cannot be avoided alt text should include the text in the image.
Avoid using images of graphs or diagrams. Where this is necessary alt text must convey the information being displayed or an accessible alternative must be provided.
In Terminal Four alt text can be added to an image by filling the “Description” field associated with the image in the media library. Leaving the description field blank will result in alt text being blank for the image. Alt text will be the same anywhere the image is included.