Alt Text for Images: Accessibility and SEO in One

Every image on your website can carry a short text that you don't even see at first glance: the alt text. "Alt" stands for "alternative", it's the description that steps in when the image itself doesn't come through. That sounds like a detail, but it's one of the most inconspicuous places where accessibility and SEO coincide. In this article I show you what alt text is for and how to phrase it so that it really makes a difference.

The nice thing about it: if you describe an image honestly and clearly, you've usually already done everything right, for people and for Google alike.

What an alt text actually is

The alt text is a short description stored in the code right next to the image. It becomes visible in three situations:

• A person uses a screen reader, software that reads out the screen. It then reads the alt text aloud, because a blind user can't see the image.
• The image doesn't load, for instance on a poor connection. Then the text appears in its place.
• Google doesn't "see" your image the way a person does. It reads the alt text to understand what's shown on it.

One and the same sentence therefore fulfils three tasks at once. That's exactly why it's worth not simply leaving it empty.

Why alt texts matter for accessibility

Imagine someone can't see your images and navigates through the page using a read-aloud function. Without alt text, this person only hears "graphic" or the meaningless file name. With a good alt text, they hear instead: "Tradesman painting a wooden facade with white paint." Suddenly the page makes sense.

Accessibility isn't just a nice gesture in Switzerland. For public bodies it's mandatory, and for private providers too it's increasingly becoming the standard. Above all, though, it's simply fair: roughly one in ten people relies on some form of support while browsing. A well-thought-out alt text costs you a minute and opens the door for these people.

Why Google loves alt texts

Search engines are getting better and better at interpreting images, but the alt text remains the clearest signal of what an image shows. You benefit from this twice over:

• Your images can appear in Google image search and bring additional visitors.
• The alt text helps Google understand the context of the whole page better, which indirectly helps the ranking.

The order in your head matters: write the alt text first for the person who hears it, not for the search engine. If the fitting search term fits in naturally, good. If not, leave it out. An honest description beats any forced keyword collection.

How to phrase a good image description

A good alt text is short, concrete and describes what is actually shown. A few simple rules of thumb:

• Concrete instead of vague: "Red racing bike against a stone wall" instead of just "bicycle".
• Keep it short: one sentence is usually enough. Nobody wants a novel read to them.
• Consider the purpose: describe what's relevant to the page. On a page about Schaffhausen, the Rhine Falls is the point, not the cloud in the sky.
• No filler phrases: leave out "image of" or "photo of". The screen reader already knows it's an image.
• Work in the important word naturally: if you're a joinery in Winterthur, "joiner at work in the workshop" may well be phrased that way, but only if it's true.

When an image doesn't need alt text

Not every image carries information. Purely decorative elements, a decorative divider, a background pattern, an ornamental flourish, don't need a descriptive alt text. On the contrary: having every decorative element read aloud would be rather disruptive for blind users.

For such cases there's the empty alt text (technically an empty alt attribute). It tells the screen reader: "There's nothing important here, skip it." That's something entirely different from leaving out the attribute altogether, because then the software often helplessly reads out the file name. This distinction is usually handled by the person who builds your page.

How to check your own images

You don't need any specialist knowledge for this. Go through your most important pages and ask yourself with each image: if I couldn't see this image, would a sentence read aloud explain what's going on here? A few pointers:

• Do the images that matter in terms of content carry an understandable description?
• Are there real sentences there, or only file names like "IMG_2043"?
• Are purely decorative images marked as such, rather than unnecessarily described?

If you stumble while reading, a screen reader probably can't make any more of it either.

Alt texts are one of those small acts of care that nobody notices as long as they're there, and that make a big difference the moment they're missing. If you like, I'll look at your existing images or set this up cleanly right from the start when building your new page. Just get in touch via the contact form, and we'll discuss what's worthwhile for you. You'll find more practical tips for SMEs in my other articles.