Missing image alt attributes cost accessibility and SEO points

Empty alt attributes are an accessibility and SEO killer, and the cost is measurable. Google Lighthouse flags the error on both of its audits: up to 6 points subtracted from the Accessibility score and 8 points from the SEO score.

The impact on real users is worse than the score. A screen reader completely ignores an image with no alt text, so blind users never know the image was there, which makes the experience disruptive and confusing. It also violates WCAG Success Criterion 1.1.1: Non-text Content, the baseline requirement for accessible non-text content.

That is why we had to act when a migration project resulted in thousands of images without an alt attribute.

A Drupal migration left 12,000 images without proper alt text

A Drupal 9 to Drupal 11 migration for a multilingual sports news project surfaced around 12,000 images with missing or incorrect alt attributes, found via Screaming Frog tool. Some images had no alt attribute at all, while others had alt text in the wrong language, with English alt text appearing on the /es version of the site.

The obvious next step was to look for a pattern. Was the issue tied to a specific content type, such as Articles? Was the wrong-language text caused by untranslated Media content? Answering these questions turned out to be surprisingly hard: Drupal provides no default mechanism, no view…