… and the text is also present as real text nearby.Use an empty alt attribute. See Decorative Images.
… and the text is only shown for visual effects.Use an empty alt attribute. See Decorative Images.
… and the text has a specific function, for example is an icon.Use the alt attribute to communicate the function of the image. See Functional Images.
… and the text in the image is not present otherwise.Use the alt attribute to include the text of the image. See Images of Text.
No:
Continue.
Is the image used in a link or a button, and would it be hard or impossible to understand what the link or the button does, if the image wasn’t there?
Yes:
Use the alt attribute to communicate the destination of the link or action taken. See Functional Images.
No:
Continue.
Does the image contribute meaning to the current page or context?
Yes:
… and it’s a simple graphic or photograph.Use a brief description of the image in a way that conveys that meaning in the alt attribute. See Informative Images.
… and it’s a graph or complex piece of information.Include the information contained in the image elsewhere on the page. See Complex Images.
… and it shows content that is redundant to real text nearby.Use an empty alt attribute. See (redundant) Functional Images.
No:
Continue.
Is the image purely decorative or not intended for users?