Alt Text That Sells: Writing for Screen Readers and Search

Alt text is the most neglected writing surface on the web, which is strange, because it’s read by the two pickiest readers your site has: people using screen readers, and search engines. Both of them consume your images as text. If the text isn’t there, or is junk, the image simply doesn’t exist for them. And on a commercial site, images are rarely decoration. They’re the product shots, the diagrams, the evidence. Skipping their alt text means publishing a version of your site with the evidence removed.

Mechanically, alt text is just an attribute on an image tag in your HTML: alt=“a short description of the image.” When a sighted visitor loads the page, they never see it, unless the image fails to load, in which case the browser shows the text in its place, a hint that its job has always been substitution. A screen reader, the software that reads pages aloud for blind and low-vision users, speaks the alt text when it reaches the image. A search engine indexes it as its primary clue to what the image depicts, which feeds both image search and its broader understanding of the page. One attribute, three consumers: the fallback renderer, the ear, and the index.

Most alt text fails in one of three ways, and it’s worth knowing all three because they fail in different directions. The first failure is absence. No attribute at all, so a screen reader falls back to reading the image’s file name, and your customer hears “IMG underscore four seven three two dot jpeg.” The second failure is emptiness of meaning: alt=“image” or alt=“photo” or the product’s SKU. Technically present, informationally void. The third failure is the SEO-brained one: alt text stuffed with keywords, “best cheap running shoes buy running shoes online running shoes sale.” This one is worse than absence, because a blind shopper has to sit through it being read aloud, and because search engines have spent two decades learning to treat keyword stuffing as a spam signal. The attempt to please the index annoys both readers.

So what does good alt text look like? The classic test is the telephone test. Imagine reading the page to someone over the phone. When you hit the image, what would you say? You wouldn’t say “image.” You wouldn’t recite keywords. You’d say the thing the image is there to convey: “a trail running shoe with a deep orange lug sole, shown from the side,” or “a line chart showing the error rate dropping after the fix was deployed.” Notice that the second example describes the point of the chart, not its pixels. That’s the craft in one sentence: describe the function of the image in the argument of the page, not its mere appearance. The same photo needs different alt text on a product page, where the buyer wants to know what the shoe looks like, than in a blog post about marathon training, where it’s just illustrating a scene.

There’s a special case that trips people up: images that convey nothing. The decorative swoosh, the spacer, the ambient background photo. For these, the correct alt text is deliberately empty, alt="", which tells screen readers to skip the image entirely. This is not laziness; it’s consideration. An empty alt attribute is a decision. A missing one is a hole. The distinction matters because it’s the difference between “nothing to say here” and “someone forgot,” and screen readers treat the two differently, guessing at the second.

Now the selling part, because the title promises it. On a store, alt text is copywriting under constraint, and constraints are where copywriting gets good. The buyer who can’t see your product photo is asking the same question every buyer asks, what am I getting, and your alt text is the only answer they’ll receive. “Blue shirt” answers nothing. “Men’s linen shirt in navy, slightly slubbed weave, shown untucked” answers like a good salesperson would. And here’s the aligned-incentives miracle: that same sentence is exactly what image search wants. Not because you stuffed keywords into it, but because honestly describing a product in concrete nouns naturally contains the words people search for. The best SEO advice for alt text turns out to be identical to the best accessibility advice: say plainly what’s in the image and why a buyer cares. When the guidelines and the algorithm and the customer all reward the same sentence, write that sentence.

When GazeSite audits a page, missing alt text is among the most common findings across every kind of site, and it shows up from two directions at once: the accessibility reviewer flags it because part of the page is inaudible, and the SEO reviewer flags it because part of the page is invisible to the index. It’s the same defect wearing two costumes, which is fitting, because the fix is one line of honest description per image.

If you do nothing else, do this: open your five most important pages, look at each image, and ask what a customer loses if that image vanishes. If the answer is nothing, mark it decorative with an empty alt. If the answer is something, write that something down, one plain sentence, phone-test quality. An hour of this is some of the highest-leverage writing you’ll do all year, precisely because it’s the writing nobody else bothered with.