AI alt text generator

Almost every tool in this category is a vision model behind an upload form: the image goes in, a description comes out. This one is not. The engine on this route accepts a string and returns a string, so the input is a written brief describing the image and its role on the page. That is a constraint of the implementation, and it is stated first rather than discovered later.

It is worth arguing about, though, because the category's standard design has a structural weakness. A vision model can enumerate what is in a frame. It cannot know why the frame is on the page, what the caption beneath it already says, or whether the image is a link. Each of those changes the correct answer, and all three are things only the author knows.

The W3C's guidance is explicit that an alt attribute should be the most concise description possible of the image's purpose. Not its contents, its purpose. Deque's framing of the same test is sharper still: if information would be missing when the image is gone, the image is informative and needs a description.

Both formulations make the same move. They locate the answer in the relationship between the image and the page, not in the image. The same photograph of a laptop on a desk is decorative in a hero banner, informative in a hardware review, and functional as a link to a product listing, and the correct attribute differs in all three cases while the pixels do not. A brief-driven tool asks about that relationship because it has to. That happens to be the right question.

Classification first, drafting second, review against the live context third. The order matters more than it looks.

Step 1

Classify the image as decorative, informative or functional. A decorative image exits the process here with an empty attribute.

Step 2

Brief the tool on subject, purpose, adjacent copy and required wording, with any formatting rule in the 300 character instruction field.

Step 3

Evaluate the draft beside the image and beside the page copy, not on its own, and cut whatever the surrounding text already delivers.

These get conflated constantly, and the distinction is mechanical rather than stylistic. An empty attribute tells assistive technology to pass the image over. An absent attribute leaves the software to improvise, which in practice often means announcing the filename. A generated sentence on a decorative image inserts content into a page that had none.

The W3C is specific about the first of these in a way that matters at the character level: the quotes must contain nothing at all, since even a space can cause an image to be announced. This is the one place where a generator actively harms a page, because a tool that always produces output will happily describe a background texture. The classification step exists to keep those images away from it.

Four recurring patterns, each with a fix that lives in the brief rather than in the output.

Redundancy

The attribute restates the caption. A listener receives both, so the duplication costs time and adds nothing. Name the adjacent copy in the brief.

Medium announcement

Opening with image of or photo of. The medium is already announced, so the phrase consumes the front of the string where the point should be.

Inventory

Exhaustive description of an informative image. Detail is not accuracy, and past a point it is an obstacle.

Data smuggling

Pushing a chart's values into the attribute. A long description is a separate technique, and the alt attribute is not where a table belongs.

It circulates widely and it is not what the sources say. The W3C expresses length as concision relative to purpose and gives no count. Deque declines a limit explicitly and argues by example: for a photograph of a house, Photo of a house carries too little, an exhaustive description carries too much, and a description naming the style, the setting and the one notable detail sits in between.

The practical consequence is that length is an output of the decision, not an input to it. A product thumbnail in a grid legitimately needs a handful of words. A diagram doing real explanatory work legitimately needs more. Asking for a short result in the instruction field is reasonable; treating brevity as correctness is not.

Input accepts 1 to 12,000 characters and is rejected outside that range. Output is capped at 1,400 completion tokens, which on this route limits how many strings a single run can return rather than the length of any one of them. The allowance is 5 runs per rolling 24 hours, counted per window rather than reset at a fixed hour. The only user control beyond the brief is a 300 character instruction passed alongside it.

What is absent is as relevant as what is present. No image upload, no CMS plugin, no browser extension, no API, no media-library scan, no bulk updater, no store catalogue connection, and no language count is claimed. Competing products in this category are built around exactly those features, which is a fair description of the trade being made here.

Output from this tool is a draft produced from a description you wrote. It cannot verify itself against the image, because it never saw the image, and it therefore cannot catch an error in your brief. Describe a declining trend as growth and you will get a fluent, confident, wrong attribute. The review beside the actual picture is not optional and is not delegable.

Nor does any of this constitute conformance. Accessibility requirements attach to the page and to the organisation publishing it, and no tool output meets them on your behalf. The honest claim is narrower and still useful: better alt text, written at the moment you still know why the image is there, which is also when search engines are given a description worth indexing.