How to Write Image Alt Text That Is Actually Useful
Write useful image alt text by describing the image's purpose, avoiding repeated captions, preserving important meaning, and leaving decoration empty.
Describe the role of the image
Alt text should help someone who cannot see the image understand what the page is doing with it. A product image may need the model and visible feature. A chart may need its main conclusion or a nearby full data table. A decorative shape usually needs an empty alternative so it does not interrupt reading.
Keep the wording concise and avoid beginning with "image of" when the screen reader already provides that context. Do not repeat a caption or nearby paragraph. If the image contains essential text, provide that text in accessible HTML as well.
Check accuracy and context
Read the paragraph before writing the alt text. The same photo can serve different purposes on a news page, product page, or personal story. Do not guess identity, emotion, or details that are not supported. For complex diagrams, use a short alt text plus a longer explanation.
- Write for the task the image supports.
- Use meaningful labels for linked images.
- Keep charts understandable without color alone.
- Review alt text when the image or page purpose changes.
Useful alt text is contextual writing. Ask whether the image identifies an object, explains a relationship, shows evidence, or simply adds atmosphere. Check the result with the surrounding heading and caption so the same information is not repeated. It gives the reader the information the image was meant to provide.