Alt text is a short text description of an image, stored in the HTML code in the alt attribute, which appears when the image cannot be displayed. Screen readers read it aloud to blind and visually impaired people, and search engines and AI systems use it to understand what the image shows. Good alt text describes the image content concretely in one sentence, without stringing together search terms.
What alt text means
Alt stands for alternative. The text is the alternative to the image for anyone who cannot see it: people using a screen reader, visitors whose image fails to load, and programs such as search engines and AI crawlers, which do not view images the way people do.
In the code, it looks like this: <img src="kueche-eiche.jpg" alt="Küche aus geölter Eiche mit schwarzer Arbeitsplatte in einem Altbau in Konstanz">. The sentence after alt= is the alt text. It is normally invisible to visitors, but it gets read aloud, read in the source code, and evaluated in image searches.
Good and bad examples for the same photo:
| Poor | Why | Better |
|---|---|---|
alt="Bild1" | Says nothing | alt="Einbauschrank unter einer Dachschräge, weiss lackiert" |
alt="Schreinerei Küche Thurgau Massivholz günstig" | Keywords instead of a description | alt="Küche aus Massivholz, gefertigt von unserer Schreinerei in Weinfelden" |
alt="Foto von unserem Team" | Too general | alt="Vier Mitarbeitende der Schreinerei Keller vor der Werkstatt" |
An example from everyday SME life
A dental practice in Wil has its website checked. Of 60 images, 52 have no alt text, and eight carry the file name, such as «IMG_4471.jpg». A visually impaired patient who wanted to call the practice booked an appointment at a different practice instead, because her screen reader only read out «image, image, image» on the page.
The practice describes every image in one sentence: «Treatment room overlooking Wil's town park», «Dr Müller explains the X-ray to a patient». The effort: two hours. After that, the website is usable for everyone, and some images appear in Google image search for «dentist Wil».
Why this matters for your business
Accessibility is the first reason. A significant part of the population relies on assistive tools or has poor eyesight, and these people are customers too. For public bodies, accessibility is required by law in Switzerland, and businesses are increasingly expected to meet it too.
The second reason is visibility. Google understands images better when the alt text describes what can be seen, and AI systems analysing a page read alt texts as part of the content. The page on image SEO explains how file name, size and format also play a role.
Common misconceptions
Alt text is not the image title and not the caption. The title appears when you hover over the image with the mouse, while the caption is visible below the image. Only the alt attribute is read aloud. And it is not a place for search terms: stacking keywords there worsens the experience for screen reader users and risks Google treating the text as spam.
Frequently asked questions
Does every image need alt text?
Every image needs the attribute, but not every one needs text. Purely decorative images such as dividing lines or background patterns get an empty attribute (alt with an empty value), so screen readers skip them. All images that carry information need a description.
How long can alt text be?
One sentence, usually under 125 characters, because some screen readers cut off longer text. Anything that doesn't fit belongs in the caption or the surrounding text. For complex graphics such as charts, the alt text describes the key point and the text next to it covers the details.
Where do I enter the alt text?
In WordPress, Wix and Shopify, there is a dedicated field for this when you insert an image, usually called «Alt text». The media library lets you edit it afterwards. Check the source code to make sure the text actually ends up in the alt attribute and not just in the title.