Describing images properly.
WHAT IT IS FOR
People using screen readers hear the alt text instead of seeing the image. It should convey what the image conveys.
It is also shown when an image fails to load, and used by search engines.
HOW TO WRITE IT
Describe what is in the image and why it matters in context.
"Blue cotton shirt, front view" for a product. "Our team outside the Ikeja office" for a photograph.
WHAT NOT TO DO
Stuff keywords. It reads badly to anyone hearing it and does not help search. Write "image of" or "photograph of". The screen reader already says it is an image. Leave it blank on meaningful images.
DECORATIVE IMAGES
Images that convey nothing, such as background patterns, should have an empty alt attribute so screen readers skip them.
Adding meaningless alt text to decorative images makes the page worse for screen reader users.
LENGTH
A sentence. If an image needs a paragraph to describe, the information should probably be in the page text as well.
FOR PRODUCT IMAGES
Describe the product specifically. This also brings traffic from image search.
