This translation has not been editorially reviewed yet. The German version is authoritative. Deutsche Fassung →
Checking alt text: when an image needs text
Every image that carries information needs alt text that conveys that information. Purely decorative images explicitly need EMPTY alt text (alt=""), so screen readers skip them. Both of these can be checked — whether the existing text actually captures the image's content, though, only a human can judge.
- The presence is measurable by machine: If the alt attribute is missing completely, this is a clear finding, and the examiner shows it with reference and measure. Equally clear are alternative texts that only repeat the file name.
- What a machine can't decide is quality. "Image1.jpg" is recognisably wrong, but whether "employee at desk" describes the image adequately, or whether it actually shows an operating step, is decided by a reviewer. That's exactly why this criterion stays open with us until a human has judged it.
- A common mistake in the other direction: alt text on purely decorative images. A screen reader then reads out "divider line", "background pattern", "decorative element" on every page visit. That's not a gain — it's noise.
