Alt text
What the AI alt text generator does, and what it cannot do
Say this part first, because every other tool on this subject works the other way round. This AI alt text generator does not look at your image. There is no upload box on this page and no vision model behind it. You write a short brief describing the picture and what it is doing on the page, and the tool writes the alt attribute.
That is a real constraint and it is worth knowing before you start. It is also the reason the output tends to be usable. The W3C's own guidance says an alt attribute should be the most concise description possible of the image's purpose, and purpose is the one thing no automatic image reader can see. You know it. The brief is where you say it.
The brief
What to put in the brief
A one-line description produces a one-line guess. Four short facts produce something you can paste straight into the markup.
- What is in the image
- The subject, plainly. A woman at a laptop in a shared office, a line chart of quarterly revenue, a product on a white background.
- What it is doing there
- Illustrating a point, showing a product, acting as a link, replacing text in a graphic. This decides almost everything about the result.
- What the surrounding text already says
- Alt text should not repeat the caption or the paragraph beside it. Tell the tool what is already on the page.
- Anything that must appear
- A product name, a person's name, the text baked into a graphic. Put it in the brief, or it cannot be in the output.
How to
How to use the AI alt text generator in three steps
Free, with 5 runs every rolling 24 hours and no account. One brief per run, so batch a few images into one brief if they belong together.
- Step 1
- Decide first whether the image needs alt text at all. If nothing would be missing when the image is gone, it is decorative and takes an empty attribute instead.
- Step 2
- Write the brief covering the four points above, and add a rule in the instruction field if you need one, such as keeping it to one sentence.
- Step 3
- Read the result against the page it is going on, then paste it into the markup. Cut anything the adjacent text already says.
Before you generate
Some images should have empty alt text, not generated alt text
A generator always returns a sentence, which is a problem when the right answer is nothing. The test is simple. Read the page aloud in your head and leave the image out. If nothing is missing, and the image is not a link or a button, treat it as decorative.
Decorative does not mean no attribute. It means an empty one, and the W3C is precise about this: there must be nothing between the quotes, because even a single space can cause a screen reader to announce the image anyway. Leaving the attribute off entirely is worse still, since a screen reader will then often fall back to reading the filename out loud.
Why it matters
Four rules the generated text has to follow
Check the output against these before it goes into your markup. The tool is aiming at all four, and you are the one who can confirm them.
- Most important thing first
- Someone listening does not skim. Put the point of the image at the start of the string, not after a run of setup.
- No image of, no picture of
- A screen reader already announces that it is an image. Those two words spend the attention you have before saying anything.
- Do not repeat the neighbours
- If the caption underneath already names the person in the photograph, the alt text saying it again is noise.
- Long descriptions go elsewhere
- A chart's actual numbers do not belong in an alt attribute. Alt says what the chart is, and the data goes in text or a table nearby.
Special cases
Logos, icons, links and images of text
These four go wrong more often than ordinary photographs do, and all four go right if the brief says what the image is for.
A logo in a header should at minimum carry the company name. Icons are very rarely purely decorative, so an icon that means something needs the meaning, not the shape: say save, not floppy disk. A clickable image needs alt describing where it goes or what it does, because for a listener that string is the link. And an image that contains text, a quote card or a banner, needs that text carried into the attribute, so paste the wording into your brief.
Straight answer
Is there a character limit for alt text?
You will see 125 characters quoted as a rule. The accessibility guidance actually says something less tidy. The W3C frames length as concision relative to the image's purpose rather than a count, and Deque's guide declines to give a number at all, arguing by example instead: for a photograph of a house, Photo of a house is too thin, an exhaustive inventory is overwhelming, and something like a modern one-story home on a quiet residential street with a brown dog in front sits about right.
So the test is not length. It is whether a listener gets what a viewer gets, minus whatever the page already says. If you want something shorter, ask for it in the instruction field and check the point survived.
In practice
Who uses an AI alt text generator, and when
The common cases are someone writing a post and stopping at the image tag, a site owner working through a backlog of pages, and a developer who has the markup but not the words. Alt text also gets read by search engines to work out what an image is about, which is why it tends to be requested by two different departments for two different reasons.
The best moment to write it is while you are placing the image, because that is when you still know why it is there. Come back to a page six months later and the reasoning has usually gone. This tool needs that reasoning as input, which makes it most useful at the moment you are authoring rather than during a later audit. Whatever comes out is a draft for you to check, not a compliance result, and nothing here claims to meet any standard on your behalf.