The image caption is the text that accompanies the image on the page – if you look at the images in this article, it’s the text in the gray box below each one. Because people use them when scanning an article. People tend to scan headings, images and captions as they scan a web page-
The alt text (or alt tag) is added to an image so there will be descriptive text in place if the image can’t be displayed to the visitor for any reason.
“In situations where the image is not available to the reader, perhaps because they have turned off images in their web browser or are using a screen reader due to a visual impairment, the alternative text ensures that no information or functionality is lost.”
“Captions under images are read on average 300% more than the body copy itself, so not using them, or not using them correctly, means missing out on an opportunity to engage a huge number of potential readers.”
