How it works
Alternative text conveys an image’s purpose when the image cannot be seen. Its wording depends on context. Informative images need a meaningful equivalent; purely decorative images usually need an empty alternative. A linked image may need to describe the destination or action, while a complex diagram also needs an accessible explanation nearby.
A realistic example
For a diagram contrasting a router and an access point, describe the connection and functional difference rather than saying only “network image”. If that same meaning is already completely explained in adjacent text, avoid making a screen reader repeat a long identical explanation.
What to check
Read the page without images and check whether the argument and actions still make sense. Inspect actual alt attributes, decorative treatment and the accessible names of image links. Translate meaningful alternatives with the page; keep model names stable when translating them would be misleading.
Limits and next steps
Do not turn alternatives into keyword lists or describe irrelevant colours and decoration. Missing alt and empty alt are not interchangeable. For charts and complex illustrations, provide the important values or relationships in normal text instead of expecting one attribute to carry the whole explanation.