Image Alt Text and SEO: What to Write and What to Skip

Missing alt text is one of the most common problems I run into. On a shop with thousands of product photos it isn't five errors, it's often a few thousand. The good news: it's one of the few SEO problems you can fix mechanically. No redesign, no developer.

What alt text is and where it comes from

Alt text is an attribute on the HTML image tag:

``html <img src="/photos/scandi-armchair-oak.jpg" alt="Scandi upholstered armchair with oak legs, grey fabric"> ``

In practice you type it in the admin — in WordPress it's the "Alternative Text" field in the media library, in shop platforms it sits next to the product image. Don't confuse it with the image title, the caption or the file name. Those are three different fields and search engines read them differently.

Alt text has one original job: to say what's in the image when you can't see the image. That covers a blind visitor using a screen reader and a browser that failed to load the file. The SEO benefit is a side effect of that job, not the other way round.

Why it matters to Google

Google can't look at a photo and tell with confidence that it's your armchair model in grey fabric. Image recognition has limits, and Google's own image documentation says alt text is its main source of information about what an image shows.

Three concrete consequences follow.

Image search. Without alt text a product photo has almost no route into Google Images. For furniture, clothing, decor or jewellery that's a real traffic channel people switch off themselves.

Page context. Alt texts help a search engine work out what the page is about. On a category page with twenty undescribed product photos you lose twenty small signals at once.

Accessibility as a quality signal. Google doesn't measure accessibility directly as a ranking factor, but sites that take it seriously tend to have cleaner markup overall. Cleaner markup indexes better.

Why it matters to customers more than to Google

A screen reader reads the alt text out loud. When it's empty, it reads the file name instead. So a visually impaired customer hears "I M G underscore two eight four seven dot jay peg" instead of "Scandi upholstered armchair, grey fabric". On a shop where ten product variants differ only by the photo, that's buying blind.

The second case is more mundane and hits everyone: slow mobile connection, the image doesn't load, and all that's left is blank space or the alt text. If nothing's there, the visitor has no idea what they missed.

How to write good alt text

The rules are short and they don't change.

Describe what's in the image, specifically. Not "armchair" but "Scandi upholstered armchair with oak legs, grey fabric". Not "our team" but "three service technicians installing an air conditioning unit".

Stay under about 125 characters. Some screen readers cut longer text off. If you need to say more, that belongs in the caption below the image, not in the alt.

Don't start with "image of" or "photo of". The screen reader already announced it's an image. Repeating it just slows the listener down.

Use a keyword only where it genuinely belongs. If the photo really shows the Scandi armchair, the word "armchair" in the alt is correct. Cramming in "armchair cheap london armchair online shop" is stuffing, and Google reads it the same way you do.

Leave decorative images with an empty alt. Dividers, shadow layers, background icons — those get alt="". An empty attribute is the correct value; it tells the screen reader to skip the element. Leaving the attribute out entirely is not the same thing and is not correct.

If the image is a link, describe the destination. When the header logo links to the homepage, the alt should read something like "Novak Furniture — homepage", not "logo".

Transcribe text that lives inside an image. Infographics, a price list saved as a picture, a banner with promo conditions — whatever is written in the image has to exist as text too. Either in the alt if it fits, or in the copy underneath.

Typical mistakes I see on shops

| Mistake | What it looks like | What to do | |---|---|---| | Empty alt on products | alt="" on a product photo | Add the product name plus a distinguishing detail | | File name used as alt | alt="DSC_0431" | Rewrite it as a description of the content | | Same alt on every photo of a product | 6× "Scandi armchair" | Distinguish the shot: front, fabric close-up, in a room | | Alt = full category name + brand | 200 characters of keywords | Cut it back to the essentials | | Alt on a decorative element | alt="background wave" | Set alt="" |

With product variants, distinguishing the shots matters more than it seems. Six photos with identical alts give neither Google nor the customer any new information. Two words are enough: "side view", "seam detail", "in a living room".

How to fill them in when hundreds are missing

One by one, by hand, you won't get through a catalogue. The process that works:

1. Find out the scale. Crawl the site and list every <img> with no alt or with an alt of only a few characters. Without a number you don't know whether you're dealing with ten images or three thousand.
2. Sort by page type. Product photos, categories, blog, decorative bits in the theme. Each group needs a different recipe.
3. Use a template for products. Most product alts can be generated from structured data: product name + colour or variant + photo order. It isn't poetry, but it's accurate, and you fix the whole catalogue in one pass.
4. Do the ones that matter by hand. Homepage images, key categories, articles that actually bring traffic. There, ten extra minutes pay off.
5. Set a rule going forward. If the alt isn't filled in automatically when a product is uploaded, in a month you'll be back where you started.

That's exactly how I handle it: when I crawl a site I find every image with no alt text, and for the findings that matter I write the actual text that should go there — not a recommendation saying "add alt text". You approve the suggestions and they go live through the WordPress plugin, the API, or you export them to CSV and bulk-upload them into the shop.

What to realistically expect

So we're clear: filling in alt texts is not the change that moves a site up ten positions. It's hygiene. The effect usually looks like this:

• image search visibility improves where the content is genuinely visual (products, interiors, food, crafts)
• the pages become usable for people on screen readers, which is both a legal and a basic decency obligation
• fewer warnings in audits, so they stop hiding more serious findings

Organic positions move slowly, and alt texts on their own are not the lever that shifts them. Anyone claiming otherwise is selling you hope. They make sense as part of a package alongside titles, descriptions and speed — which is why I measure the impact of every deployed fix 28 days before and after, so it's visible what actually worked.

A five-minute check

Open any product page, right-click the main photo and choose "Inspect". Look at what's in the alt attribute. If you see a file name, an empty string, or no attribute at all, you have your answer — and there's a good chance the same is true across the whole catalogue.

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