Image Alt Text: The SEO Win Most Merchants Skip

Every Shopify store has a list of SEO jobs nobody’s doing. Alt text sits at the top of it, and it’s the strangest entry on the list, because unlike rewriting four hundred product descriptions, this one is easy.

A sentence per image. No strategy, no keyword research, no deciding what your brand voice is. And yet open your media library right now and count how many product photos have an empty alt field. For most catalogs past a few hundred SKUs, the honest answer is most of them.

The reason isn’t laziness. It’s that alt text is trivial per image and enormous in aggregate, which is exactly the kind of work that never gets started. It’s also the first thing FullSweep SEO generates when it sweeps a store, for that reason precisely.

What is alt text actually for?

Two audiences, in this order.

Someone using a screen reader gets the alt attribute read aloud in place of the image. If it’s blank, they hear the filename, which on a Shopify store is usually something like IMG_4471_final_v2.jpg. Sometimes they hear nothing at all. Either way, whatever that photo was communicating is gone.

The second audience is search engines, which use alt text to understand image content. Google’s own guidance treats it as a primary signal for image search, and it’s the reason a photo can rank for a query that never appears in your page copy.

The order matters. Alt text was built as an accessibility feature and picked up an SEO benefit later. Writing it primarily to please Google is how you end up with the keyword-stuffed garbage in the next section.

Where does the traffic actually come from?

Google Images, mostly, and it’s an underrated channel in visual categories.

Think about how people shop for a sofa, a ring, a rug, a jacket. They search, click Images, and scroll until something looks right. Then they click through to the store. That’s a shopper arriving at your product page with intent, and the thing that got them there was a photo Google understood well enough to surface.

If your alt text is blank, Google is working from the filename, surrounding text and whatever its own image recognition can infer. That’s not nothing. It’s just considerably worse than being told.

There’s a second effect worth knowing about. AI assistants increasingly reason over pages that include images, and alt text is part of how they read what’s on a page. A product page describing its own photos gives more to work with than one that doesn’t.

What does bad alt text look like?

Four failure modes, all common.

Empty. The default. Nothing to say about it.

The filename. DSC_0847.jpg, or worse, blue-shirt-1-1-1-copy.jpg. Technically not blank, functionally useless.

Keyword stuffing. “Womens blue silk blouse buy online cheap silk blouse best silk blouse ladies top.” Search engines caught onto this roughly two decades ago, screen reader users find it painful, and it’s the one version of alt text that can actively hurt you.

Redundant framing. “Image of a blue blouse.” A screen reader has already announced that it’s an image. You’ve added two words of nothing to every image on the site.

So what does good alt text look like?

Describe what’s in the photo and what it tells a shopper, in one sentence, in normal English.

For a product hero shot: “Navy linen blouse with three-quarter sleeves, shown untucked over cream trousers.”

For a detail shot of the same product: “Close-up of the mother-of-pearl button cuff on the navy linen blouse.”

For a scale shot: “The 5-quart mixing bowl next to a standard stand mixer, roughly the same height.”

Notice that each one describes something different. This is the part people miss when they bulk-copy the product title into every image. Your fourth photo exists because it shows something the first three don’t. Say what that is.

Keyword inclusion happens naturally when you write accurately, because the accurate description of a navy linen blouse contains the words navy, linen and blouse. That’s the entire trick. You don’t have to force anything.

What about images that aren’t products?

Two categories worth handling deliberately.

Decorative images should have an empty alt attribute, deliberately empty rather than missing. Background textures, dividers, that abstract shape in your hero section. An empty alt tells a screen reader to skip it silently, which is what you want. Describing it just adds noise.

Informational images that aren’t products need real descriptions, and these are the ones most stores forget entirely. Size charts, care instruction graphics, comparison tables saved as images, ingredient lists on a packaging photo. If information exists only inside an image, it’s invisible to search engines and to anyone using a screen reader. Ideally that content lives as text on the page too. At minimum, describe it properly.

Why does this get skipped at catalog scale?

Do the arithmetic and it explains itself.

A thousand products with an average of four photos each is four thousand images. At even thirty seconds apiece — open the image, look at it, write a sentence, save — you’re at over thirty hours. That’s a full working week to describe photographs, and nobody has that week. So it stays on the list, and the list gets longer every time you add a product line.

This is the shape of problem that makes alt text a good candidate for automation. It’s high volume, low judgment, and highly repetitive, but it does require actually looking at each image rather than pattern-filling from the product title. FullSweep SEO writes alt text as part of its whole-store sweep, and like every other change it makes, each one arrives as a before/after diff you approve, edit or skip before anything publishes. Bulk handles the volume; you stay in control of what goes live. The flow is at how FullSweep SEO works.

Where should you start?

If you’re doing this by hand, don’t start at the beginning of your catalog. Start where the return is highest.

Your top twenty products by traffic. Then any product in a category where people shop visually, since that’s where image search actually converts. Then your collection page banners and hero images, which are usually few in number and completely undescribed.

Skip the theme decoration entirely, and give it an empty alt if it doesn’t have one.

One last thought on why this is worth doing even setting search aside. Some percentage of your customers use a screen reader, and right now your store is telling them IMG_4471. Fixing that is a couple of sentences of work per product, and it happens to be the same work that gets you into Google Images. Rare to find a job where the right thing and the profitable thing are the identical task.