Write Useful Alt Text for AI-Generated Images
Alt text should serve the image's purpose in the page. It is not automatically a detailed description of every visible object or a place to add keywords. For an AI-generated image, review the actual output and decide what information the reader needs from it in this particular context.
Why it matters
The same image can have different roles. A decorative illustration, a link image and an instructional diagram each need different treatment. The surrounding text also affects what information is already available.
A practical workflow
- Identify whether the image conveys information, performs a function or only adds decoration to the page.
- For informative images, describe the relevant meaning concisely rather than listing every colour and background detail.
- For a linked image, ensure its accessible text explains the destination or action the link performs.
- Give complex diagrams an appropriate longer explanation in the page, and check the result with the surrounding content.
An example
A generated illustration of a student beside a laptop may be decorative in an article about study habits. A diagram showing a document moving through a retrieval pipeline conveys specific steps and needs an explanation of those relationships.
A mistake to avoid
Do not reuse the generation prompt as alt text. A prompt can describe intentions that the image failed to produce. Also avoid presenting a generated scene as evidence of a real event through its caption or description.
Try it and check the result
Read the page with the image descriptions included and imagine the images are unavailable. The essential meaning and actions should remain clear without unnecessary repetition or a long catalogue of decorative details.
Reference and further reading
W3C WAI: choosing appropriate image alternatives.
The workflows and examples in this guide are illustrative. Product controls and availability can change; check the linked official guidance for your setup.
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