How to Write Useful Alt Text for AI-Generated Images
Write concise, contextual alt text for AI illustrations, realistic synthetic scenes, product concepts, charts, and decorative images without keyword stuffing.
Alt text is not a caption hidden for search engines. It is a functional replacement for an image when a reader cannot see it or when the file fails to load.
AI-generated images do not require a completely different accessibility method, but they create two recurring questions: whether to mention that the image is synthetic, and how to describe a picture that contains attractive detail but little actual information.
The answer starts with context.
Describe the image's job, not every visible object
The same image can need different alt text on different pages.
Suppose an illustration shows a ceramic cup beside a notebook in morning light. On an article about writing routines, useful alt text might be:
Ceramic cup and open notebook on a desk in soft morning light.
On a page teaching composition, the relevant information changes:
Cup placed in the left third of a horizontal composition, with open writing space on the right.
Both are accurate. The second version explains why the image is present on that particular page.
Keep decorative images out of the way
If an image adds atmosphere but no information, use empty alt text: alt="". A screen reader can then skip it.
Examples include a background texture, an abstract glow behind a heading, or a repeated thumbnail when the adjacent linked title already provides the same destination. Describing every decorative flourish makes a page tiring to navigate.
Do not omit alt text simply because writing it is inconvenient. First decide whether the image carries information. If it does, provide the replacement.
Mention AI generation when it prevents confusion
Alt text should usually describe the content, not the production tool. "AI-generated image of" repeated across a gallery can bury the useful part.
Mention the synthetic nature when realism could cause a reader to mistake the scene for evidence, documentation, or a photograph of a real person or event:
AI-generated illustration of a proposed car-free town square with trees and outdoor seating.
That wording helps readers understand that the picture is a concept, not a record of a completed project.
Disclosure may also belong in a visible caption or nearby text. Alt text should not carry an important disclosure that sighted readers never receive.
Do not copy the prompt
Prompts contain production instructions that do not help someone understand the result: lens names, rendering engines, quality terms, negative prompts, and discarded details. They may also describe things the model failed to produce.
Write alt text from the final image and its role on the page. If the prompt asks for five candles but the image contains four, the alt text should not repeat the planned count.
Handle text inside images carefully
If visible words are important, include them or provide the same information in nearby page text.
For a poster concept:
Blue event poster reading "Night Market, Friday 7 PM," with illustrated food stalls under string lights.
If the generated lettering is nonsense, do not transcribe it as though it were meaningful. Remove or replace the bad lettering before publication when it distracts from the image.
For charts and diagrams, a short alt description is rarely enough. Summarize the main conclusion in surrounding text and provide the underlying values or a longer description where readers can access them.
Product concepts need honest wording
Alt text should not turn a concept into a factual product claim.
Use:
Concept image of a matte green reusable bottle on a stone counter.
Avoid:
Our new leak-proof bottle made from recycled steel.
The second version asserts features the picture cannot prove. For a real listing, describe the actual product photo and keep material, size, and performance claims in verified page copy.
A useful length test
There is no single perfect character limit for every situation. Aim for one concise sentence when one sentence can replace the image. Stop when the reader has the information needed to follow the page.
Remove openings such as "image of" or "picture of" unless the medium matters. Screen readers already announce that an image is present. "Watercolor illustration of..." can be useful in an art tutorial; "image of a person" usually wastes the first words.
Names, identity, race, gender, disability, age, and emotion should be included only when visible, relevant, and described with care. Do not guess a sensitive attribute or identify a generated face as a real person.
Five before-and-after examples
Too vague:
AI art.
Better:
Paper-cut illustration of a lighthouse surrounded by layered blue waves.
Keyword-stuffed:
Free AI image generator AI art tool text to image example.
Better:
Neon-lit noodle shop reflected in a rain-soaked street at night.
Prompt copied into alt text:
Cinematic 35mm award-winning ultra-detailed portrait, volumetric light.
Better:
Close portrait of an older violinist playing beneath a streetlight in light rain.
Missing context:
Three rectangles.
Better:
The same product framed in square, portrait, and landscape crops.
Unnecessary description for decoration:
Purple and blue blurred gradient background.
Better:
Empty alt text.
Add alt text during editorial review
Do not leave accessibility until after upload, when filenames and context are easy to forget. Write alt text while reviewing the final crop. The crop matters: do not describe a person who was removed from the mobile version.
Use the AI image quality checklist to review anatomy, words, reflections, claims, crop, and rights before writing the final description. If the image cannot be described honestly without revealing that it is confusing or misleading, the problem is the image, not the alt text.
