"Image SEO: How to Write Alt Text That Helps You Get Found"

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Short answer: Alt text is a short written description of an image that Google and screen readers read instead of seeing the photo. Write what is actually in the picture in plain words, like "Dalmatian puppy playing fetch," not "puppy" and not a list of keywords. Do that for every meaningful image and you help both search and shoppers.

That one habit, describing the photo honestly, is most of image SEO. The rest is housekeeping: name the file before you upload it, keep the file small so the page loads fast, and add a caption only when it earns its place. Below is the order to do it in, with a bakery's sourdough photo and a plumber's before-and-after shot to show the weak version next to the strong one each time.

Two readers benefit from the same work. Google reads your description to decide what the image shows and whether to surface it in Google Images. A blind or low-vision visitor using a screen reader hears that same description read aloud. Google says alt text "improves accessibility for people who can't see images on web pages, including users who use screen readers." Serve one and you serve the other.

Name the file before you upload it

Open your camera roll and you will see filenames like `IMG00023.JPG` and `DSC_0421.jpg`. Those tell Google nothing. Rename the file to describe the photo, in lowercase, with hyphens between words, before it ever touches your site.

The bakery's sourdough photo goes from `IMG00023.JPG` to `sourdough-loaf-sliced.jpg`. The plumber's shot goes from `DSC_0421.jpg` to `bathroom-leak-repair-before-after.jpg`. Short, readable, and obvious to a person and a machine.

Google says the filename "can give Google very light clues about the subject matter of the image. When possible, use filenames that are short, but descriptive. For example, `my-new-black-kitten.jpg` is better than `IMG00023.JPG`." It explicitly tells you to avoid generic names like `image1.jpg`, `pic.gif`, and `1.jpg`. Light clues are still clues. Rename the file and you have spent thirty seconds buying yourself a free signal. This is the same habit that helps your written content get found, which is why we walk through it again in the on-page SEO basics.

Describe what is actually in the photo

Alt text, short for "alternative text," is the written description you attach to an image. Every website builder has a box for it, usually labeled "alt text" or "alternative text," right next to where you upload or click the photo. Your job is to fill that box with a plain sentence describing what the picture shows, in the context of the page it sits on.

Google illustrates the standard with a quality ladder for a photo of a Dalmatian puppy. No alt text at all is "Bad." `alt="puppy"` is "Better." `alt="Dalmatian puppy playing fetch"` is "Best." The best version is not longer because it is stuffed with words. It is longer because it actually describes the picture. Google's guidance is to "focus on creating useful, information-rich content that uses keywords appropriately and is in context of the content of the page."

Keep it short. Harvard's Digital Accessibility Services advises: "Keep it short, usually 1-2 sentences. Don't overthink it." It also says to "consider key elements of why you chose this image, instead of describing every little detail." A sentence or two is the target, not a hard character count. Some guides quote a strict 125-character rule; that is an old screen-reader convention, not a real limit. Aim for short and complete, and move on.

One more Harvard note that saves you words: there is "no need to say 'image of' or 'picture of,'" because a screen reader already announces that it is an image. But "do say if it's a logo, illustration, painting, or cartoon," because that context is not obvious from the picture alone.

See the weak and strong versions side by side

Principles are easy to nod at and easy to forget. Here are both running examples with the weak alt text next to the strong one, so you can copy the pattern.

The bakery's sourdough photo:

Weak: `alt="bread"`
Weak in the other direction: `alt="sourdough bread loaf artisan bakery fresh baked sourdough near me best sourdough"`
Strong: `alt="Sliced sourdough loaf with an open crumb on a wooden board"`

The plumber's before-and-after photo:

Weak: `alt="plumbing"`
Weak in the other direction: `alt="plumber leak repair emergency plumber near me cheap plumber 24 hour"`
Strong: `alt="Bathroom sink before and after a leaking pipe repair"`

The strong version describes the photo. The stuffed version describes nothing; it lists search terms. Google warns directly against this, saying filling alt attributes with keywords (keyword stuffing) "results in a negative user experience and may cause your site to be seen as spam." The natural keyword is already in the honest description. "Sourdough" and "leak repair" show up because they are genuinely in the picture, not because you forced them.

People who audit product photos at scale see the same failure on repeat. The team at AltText.ai, who write alt text for online stores, describe a common pattern where "every image labeled 'Product image' or simply the brand name repeated across thousands of photos, which wastes an opportunity and provides no useful information to users or search engines." Their fix is to "name the product, list the visible attributes a buyer would care about, and skip the marketing fluff," so a mug becomes "Matte black ceramic mug with bamboo lid" rather than "Coffee cup" or "Mug image." That is the bakery and plumber examples in a different shop: say what the thing is and what a buyer would notice.

In the image work we have done for owner-run small businesses, the photos are rarely the problem. The owner has good pictures, taken on a decent phone, of real products and real jobs. What is missing is the thirty seconds of describing each one. The fix is almost never "shoot better photos." It is "tell us, and the customer, and Google, what is in the photo you already have." Once an owner sees the weak-versus-strong list above, they stop writing `alt="bread"`. If you write product descriptions for the same items, the alt text is often a one-line version of work you have already done.

Compress images so the page loads fast

A photo straight off a phone can be several megabytes, far larger than it needs to be on screen. That weight slows your page down, and a slow page loses customers and rankings. Google states plainly that "images are often the largest contributor to overall page size, which can make pages slow and expensive to load." Compressing them is not optional polish; it is often the single biggest speed fix on a page.

"Compress" means shrink the file size without making the photo look worse to the eye. Two moves do most of the work. First, resize the image to the size it actually displays. If your sourdough photo shows at 800 pixels wide, do not upload one that is 4,000 pixels wide. Second, save it in a modern format. WebP is a newer image format that holds the same quality at a smaller size than an old JPEG, and every current browser supports it. Many site builders convert to it for you.

There is a payoff beyond speed. Google notes that sharp, high-quality images are more appealing as result thumbnails and "can increase the likelihood of getting traffic from users." A crisp, fast-loading sourdough photo can be the thumbnail that earns the click in Google Images. A blurry, heavy one will not. If you run a store, the same speed work pays off across every product page, which is why it shows up in the Shopify SEO checklist too.

Add a caption only when it earns its place

A caption and alt text are not the same thing, and they are not interchangeable. Alt text lives in the code and is read aloud by screen readers or read by Google; most sighted visitors never see it. A caption is the visible line of text printed under the photo that everyone reads.

Use a caption when it adds something the picture cannot say on its own. The plumber's before-and-after shot might carry a caption like "Same vanity, two hours of work," giving the photo a story. The bakery's sourdough probably needs no caption at all; the page already says it is sourdough. Do not copy your alt text into the caption. They have different jobs, so let them say different things. When you have nothing to add, skip the caption and keep the page clean.

Leave decorative images blank on purpose

Not every image needs a description. A background swirl, a divider line, a purely ornamental flourish that adds nothing to the meaning of the page: these are decorative, and the right move is to give them an empty alt text, written as `alt=""`. That tells a screen reader to skip the image entirely instead of announcing a meaningless one.

This is not a loophole; it is the standard. The web accessibility rules carve out exactly this exception. The point is that alt text describes meaningful images and gets out of the way for the rest. A good rule: if removing the image would lose information, describe it; if removing it would change nothing, leave the alt empty.

Why this serves customers and Google at once

Writing good alt text is not only an SEO move. It is a formal accessibility requirement. The Web Content Accessibility Guidelines, the standard most accessibility laws point to, include Success Criterion 1.1.1 "Non-text Content" at Level A, the most basic level of conformance. It requires that "all non-text content that is presented to the user has a text alternative that serves the equivalent purpose," with limited exceptions such as the decorative images above.

Read that plainly: a blind customer using a screen reader is supposed to be able to understand your sourdough photo and your before-and-after shot from the words you wrote. When you describe the photo well, that customer can shop, and Google can index, from the same sentence. You are not doing two jobs. You are doing one job that two audiences depend on. That is the whole reason image work is worth the thirty seconds per photo.

If you want the rest of the on-page picture, the same describe-it-plainly habit drives your page titles and your meta descriptions. Images are one more place the words you choose decide whether you get found.

Frequently asked questions

Do I really need alt text on every image?

On every meaningful image, yes. If the photo carries information, a product, a job, a person, a place, describe it. Purely decorative images, like a divider or a background pattern, are the exception: give them an empty `alt=""` so screen readers skip them. The test is simple. If removing the image would lose information, it needs a description.

How long should alt text be?

Short, usually a sentence or two. Harvard's accessibility team puts it as "keep it short, usually 1-2 sentences. Don't overthink it." Describe the key elements of why you chose the image, not every pixel. You will see a "125 character" rule quoted online, but that is an old convention, not a real technical limit, so do not stress over the exact count.

Will keyword-stuffing my alt text rank me higher?

No, and it can hurt you. Google says stuffing keywords into alt attributes "results in a negative user experience and may cause your site to be seen as spam." Write the honest description and the real keyword usually appears on its own, because it is actually in the photo. "Sliced sourdough loaf" already contains "sourdough."

What is the difference between alt text and a caption?

Alt text is the hidden description that screen readers and Google read; most visitors never see it. A caption is the visible line under the photo that everyone reads. Use alt text on every meaningful image, and add a caption only when it tells the reader something the picture cannot. Do not copy one into the other.

Describing your photos is the cheapest SEO work you will ever do, and it is the kind of small, repeatable task that quietly compounds across every page. Fonzy handles this sort of on-page detail automatically, so the filenames, alt text, and image sizes are right without you checking each one. Start with the weak-versus-strong list above, fix the photos you already have, and let the rest run on its own. For more groundwork like this, the small business website tips cover the next steps.

Sources

Roald

Founder Fonzy. Obsessed with scaling organic traffic. Writing about the intersection of SEO, AI, and product growth.