This is a fantastic post that “contains everything you need to know about alt-texts! When to use them and how to perfectly craft them.” The post is written by Daniel Göransson, a visually-impaired screen reader user and front-end developer.
Writing proper alternative text for images is of utmost importance for anyone and everyone who cannot see those images, especially screen reader users. Thus the importance of writing proper image descriptions.
The content of the alt-text is not always what you’d expect, though. Daniel covers all possible implementations with hints to the kind of descriptive text you should write, which pretty much depends on the context in which the image is written or embedded.
Nicolas Steenhout has a thread of tweets that also contains a few complementary tips that are worth checking out.
Daniel’s article is a must-read for anyone interested in learning how to write proper, accessible, usable alt-text for images.
Read the article for all the details.