Alt text for AI agents: describing product images
Usually fixed by: SEO or content team · Typical effort: days
Your product photos do a lot of selling. They show the color, the cut, the size in someone's hand. Most AI agents never see them. What they read instead is the alt text: the short description attached to each image in your HTML. If it's missing, the photo might as well not be there.
Why images are a blind spot for agents
An AI agent helping someone shop usually reads your page as text. It fetches the HTML, strips out the layout and works from what's left. Images arrive as file names and URLs, which tell it very little. IMG_4471_final.jpg doesn't say whether the jacket is navy or black.
Some agents do look at the page as a picture, taking screenshots and reading them with a vision model. They can make out a photo, but slowly, at a cost, and not always correctly. Text is faster, cheaper and unambiguous, so even those agents lean on it when it's there.
Alt text is the bridge. It's an attribute on the image tag, written for anyone who can't see the image: screen reader users, people on slow connections, search engines and now AI agents. Writing it well is the same work for all of them. We make that case in Accessibility work is agent readiness work.
What AgentScore checks
The "Images have text descriptions" check is part of the Readability category. It loads your home page in a real browser and looks at the images people can actually see, ignoring tiny ones under 32 pixels wide such as icons and tracking pixels. For each one it asks a simple question: does it have an alt attribute at all?
| Result | What it means |
|---|---|
| Pass | 90% or more of visible images have alt text, or there are no content images on the page |
| Warning | Between 60% and 90% have alt text |
| Fail | Fewer than 60% have alt text |
An empty alt="" counts as described. That's deliberate: it's the correct way to mark an image as decorative, and it tells agents and screen readers to skip it. The check can't judge whether your descriptions are any good, so that part is up to you.
It's a small check by weight, because a missing description rarely stops an agent on its own. But the same gaps tend to show up elsewhere. A linked product image with no alt text is also a link with no name, and that's caught by the "Buttons and links have names" check in Navigability, which carries more weight.
How to write alt text for product images
Describe what a shopper needs to know from the photo, in the words they'd use. Lead with the product, then add the details the image actually shows.
| Weak | Better |
|---|---|
alt="product" | alt="Northwind waxed cotton field jacket in navy, front view" |
alt="IMG_4471" | alt="Field jacket in navy, close-up of brass zip and corduroy collar" |
alt="best jacket waterproof jacket mens jacket sale" | alt="Model, 6 ft 1 in, wearing the field jacket in size L" |
| No alt attribute | alt="" if the image is purely decorative |
- Name the product and the variant. If the photo shows the navy version, say navy. Agents use this to match images to options.
- Say what's different about each shot. Front, back, detail, in use, on a model. Five images all called "Field jacket" waste the opportunity.
- Include facts the photo proves. Model height and size worn, what's in the box, the scale of an object next to something familiar.
- Keep it short. One short sentence is usually enough. Long specifications belong in the product description, not the image.
- Don't stuff keywords. Agents read alt text as a description. A list of search terms reads as noise and helps nobody.
- Don't start with "image of". Everyone reading it already knows it's an image.
Decorative images, logos and linked images
Not every image needs words. Background textures, divider graphics and lifestyle photos that repeat the headline next to them can take alt="". That's different from leaving alt out: an empty value says "nothing to see here", while a missing one leaves agents and screen readers guessing, and some will read out the file name instead.
Images that are links need extra care, because the alt text becomes the link's name. A product tile where the whole image links to the product page should have alt text that works as a link, such as the product name. Your logo in the header links home, so alt="Northwind home" or simply your brand name works better than alt="logo".
Text baked into images is a common trap on home pages. A banner that says "40% off outerwear this weekend" as pixels is invisible to most agents. Put the offer in real HTML text over the image, or at minimum repeat it in the alt text.
Doing this at catalog scale
A store with thousands of products can't write every description by hand. You don't need to. Most of it can be generated from data you already have.
- Fix the template first. Make sure your theme outputs an
altattribute on every product image, and falls back to the product name and variant when no custom text is set. That alone gets most stores to a pass. - Use the image metadata your platform stores. Shopify, WooCommerce, Magento and most other platforms have an alt text field per image. Fill it on new products as part of the listing checklist.
- Backfill your bestsellers. Write proper descriptions for the products that earn the most, where shoppers are most likely to ask an assistant about them.
- Review generated text before publishing. Tools that write alt text with AI are useful for a first draft, but they can describe the wrong color or invent details. Check a sample, especially for variants.
- Add it to the content workflow. Merchandisers and content teams usually own this, not developers. Make alt text a required field when new images are uploaded.
Check it yourself in a minute: open a product page, right-click a photo and choose Inspect. Look for alt="…" on the <img> tag. If it's missing, or it just says "image", agents are getting nothing.
Where alt text fits
Alt text is the visual part of a bigger job: making sure everything a shopper learns from your page is also available as text. The other parts are prices and stock in a form agents can read (see Prices AI agents can read and Product data that AI shopping agents can read), and content that's in the HTML rather than added by JavaScript (see our guide to JavaScript-only content).
Run AgentScore to see how your home page does, then spot-check a few product pages by hand. For the full picture of what agents need from a site, start with the agent readiness guide.