How to write a good image alt text

This decision tree Show archive.org snapshot describes how to use the alt attribute of the element in various situations. For some types of images, there are alternative approaches, such as using CSS background images for decorative images or web fonts instead of images of text.

Questions asked:

• Does the image contain text?
• 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?
• Does the image contribute meaning to the current page or context?
• Is the image purely decorative or not intended for users?

Follow the link for the answers.