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Check the alt text of every image on a page
Enter a page address and every image a visitor can see is checked: missing alt attributes, linked images and image buttons that leave the control with no name, file names and placeholder words used as alt, and alt text that repeats the caption or link beside it. Turn on the AI review and a vision model looks at up to eight images in context and suggests better text.
Good alt text depends on what the image is doing
The same photo can need a full sentence on one page and nothing at all on another. Before writing alt text, decide what the image does there.
| Kind of image | What the alt should say | Example |
|---|---|---|
| Informative | What it shows that matters here, in a phrase or a sentence | Volunteers planting trees along the canal towpath |
| Functional (links and buttons) | Where the link goes or what the button does | Acme home page; Search; Next photo |
| Decorative | Nothing: alt="", so screen readers skip it | A wave divider; a photo beside the same words in the same link |
| Complex (charts, diagrams, maps) | The point it makes, with the detail in nearby text or a linked description | Bar chart: sales doubled between 2023 and 2025 |
| Text in images | The words shown, when they matter | Summer sale: 30% off all lamps |
Avoid starting with “image of” or “picture of”: screen readers already say it is an image. Text in images is better as real text where possible, which 1.4.5 Images of Text asks for at Level AA, and logos are the exception. For charts, the accessible charts guide covers the data table that makes the real text alternative. Our guide on how to write alt text shows good alt text for each kind of image, with examples.
Need a first draft for a single image? The AI alt text generator writes one from an upload or an image address. To see the name every control on a page exposes, not only the images, use the accessible name previewer.
What the checker looks for
Failuresare problems a rule can be sure of: no alt attribute, a link or button whose only content is an image with no text alternative (including an icon hidden with aria-hidden), a file name such as IMG_2041.jpg used as alt, placeholder text such as “image” or “logo” on its own, and role="img" with no name. These fail 1.1.1 Non-text Content, and for links and buttons 2.4.4 Link Purpose or 4.1.2 Name, Role, Value as well.
Needs reviewcovers things that are usually wrong but need a person to confirm: alt over 150 characters, alt that repeats the caption or the link's own text, the same alt on images of different files, “click here” or “link to” in alt, an SVG with no name that is not hidden, and an image named only by its title attribute.
Decorative and finemeans alt="" (or an equivalent) on an image that is not the only content of a link or button. The rules accept it; whether the image really is decorative is a judgement, which is one thing the AI review looks at.
What it cannot tell you
- Whether alt text is accurate. A rule cannot see the picture. The AI review can, but it works from a screenshot and a little nearby text, and it makes mistakes. A person who knows what the page is for decides.
- Images it does not reach: CSS background images (counted, not checked), images inside frames, canvas drawings, icon fonts, and images that appear only after a click or a form step.
- More than one page at a time, or more than the first 300 images on a page. Some sites block automated browsers, and those cannot be checked at all.
Frequently Asked Questions
What does the alt text checker check?
Every img (including those inside picture), image button, image map area, element with role="img" and inline SVG that a visitor can see. It fails images with no alt attribute, links and buttons whose only content is an image without a text alternative, file names and placeholder words used as alt, and role="img" with no name. It flags for review alt text over 150 characters, alt that repeats the caption or the link's own text, the same alt on different images, "click here" or "link to" in alt, SVGs with no name that are not hidden, and images named only by a title attribute. Hidden images and tracking pixels are skipped.
When should an image have an empty alt attribute?
When it adds nothing a screen reader user needs: a decorative flourish, a divider, a background-style photo, or an image whose meaning is already in the text right next to it, such as a product photo beside the product name inside the same link. alt="" tells assistive technology to skip it. Never leave the attribute out instead, because many screen readers then read the file name. And never use alt="" on an image that is the only content of a link or button, because the control is then left with no name.
What should the alt text of a linked image or icon button say?
What the control does, not what the picture looks like. A logo that links to the home page should say something like "Acme home page" or just "Acme"; a magnifying glass button should say "Search". If the link or button already has visible text, give the image alt="" so the name is not read twice. WCAG 2.4.4 Link Purpose and 4.1.2 Name, Role, Value both depend on this.
How long should alt text be?
WCAG sets no limit. Most good alt text is a short phrase or sentence, because a screen reader user cannot skim it or jump back a few words. This checker flags anything over 150 characters for review rather than failing it: long descriptions usually belong in a visible caption or nearby text, and complex images such as charts need a short alt plus a fuller description elsewhere on the page.
How does the AI review work, and what does it cost?
Tick the AI review box and the checker picks up to eight images, starting with those missing alt, then images that are the only content of a link or button, then large images. Each is captured as a screenshot on its own and sent, with its current alt and nearby text, to a third-party vision model, which judges whether the alt fits and suggests better text. Without an account you get two reviews a day; signed in, a review costs 2 credits. Nothing is charged if the review does not complete. The rule checks are always free.
Does a clean result mean the page meets WCAG 1.1.1?
No. Rules can find alt text that is missing or malformed, but not alt text that is wrong: "Two people at a desk" passes every rule even if the photo shows a bridge. The AI review is a second opinion and can be wrong too. Whether each image's text alternative serves the same purpose is a judgement a person has to make, and 1.1.1 also covers CSS background images, canvas, icon fonts, audio and video, which this tool does not check.
Essential Accessibility Resources
Comprehensive tools, checklists, and guides to help you create inclusive digital experiences