Alt text provides a text alternative for an image. Its purpose depends on the role the image plays in the page, rather than simply describing everything visible.
It is particularly important for people using screen readers and in conditions where an image cannot be displayed. Useful alt text preserves the information or function that would otherwise be lost.
How do you decide what to write?
Ask what the image contributes to the surrounding content. An informative photograph, a linked icon and a decorative background have different jobs.
The alternative should serve the same purpose. A product detail image may need a specific feature described, while a linked logo may need to identify its destination.
Do decorative images need a description?
Purely decorative images can use an empty alternative so assistive technology does not add unnecessary information. This differs from simply forgetting the attribute.
Context matters. The same image can be informative in one location and decorative in another. Make the decision where it is used.
What about charts and diagrams?
A short alternative may identify the subject, while a longer explanation or accessible data presentation communicates the detail. Complex information often needs more than one sentence.
Do not assume a chart becomes accessible by adding “sales graph”. The reader still needs a way to obtain the meaningful relationships or values being communicated.
Is alt text an SEO field?
Search engines can use image context, including alt text, but accessibility and meaning should guide the wording. Repeating keywords without describing the relevant information does not fulfil the role.
Avoid using every image as another place for a company slogan. The alternative should be useful to someone who needs it.
How should editors manage it?
A CMS should make alternatives easy to enter and review. Editors need guidance about informative, functional and decorative images rather than a rule demanding a long description for everything.
Review changes when an image is replaced or reused. Copying old alt text onto a different image can introduce inaccurate information.
How do you check quality?
Read the page's content without relying on the image. Ask whether the alternative supplies the missing meaning without repeating material unnecessarily.
For functional images, check whether the action remains clear. For informative images, confirm that relevant detail is communicated at the right level.
Common mistakes
Avoid file names, vague labels and long descriptions that add no useful information. Also avoid omitting essential text shown inside an image when it is not available elsewhere.
The strongest alternative is usually concise and purpose-driven. A more complex visual may require a fuller accessible treatment beside it.
Further reading
For reference, see the supporting documentation. Explore related explanations of Website accessibility, Content management system, User experience.
A practical example
Illustrative example: a product image highlights a folding mounting hook. Its alternative describes that feature in the product context. A decorative texture behind the heading receives an empty alternative, because announcing it would not help the reader understand the page.
Why it matters
Alt text helps preserve the meaning and functionality of images. Treating it as part of content design makes the page more useful than treating it as a keyword box.
