- Element Code: ON-029
- Issue: Informative images have empty or missing alt text
- Impact: Accessibility failure for screen readers; lost image-search context
- Fix: Write concise, descriptive alt text for informative images; keep decorative images empty
- Detection: Screaming Frog, accessibility audits, WAVE
What this issue means
The alt attribute describes an image for people using screen readers and for search engines that can't "see" the picture. Informative images (charts, product photos, diagrams) need descriptive alt text. Decorative images that add no information should have an empty alt="" so assistive tech skips them — that's correct, not a bug.
Why it matters
Alt text is both an accessibility requirement (WCAG) and an SEO signal: it gives Google Images context and reinforces the page's topic. Missing alt on informative images means screen-reader users lose meaning and you forfeit image-search visibility.
How to fix it
- Describe the content and function of the image in a sentence fragment ("Bar chart showing AI Overview citation rates by ranking position").
- Keep it concise — roughly under 125 characters.
- Include a keyword only if it's genuinely relevant; never stuff.
- Skip "image of" / "picture of" — screen readers already announce it's an image.
- Leave decorative images empty (
alt=""), not undefined. - In WordPress, set alt text in the Media Library; bulk-edit plugins can fill gaps.
Common mistakes
- Using the file name (
IMG_4821.jpg) as alt text. - Keyword-stuffing alt attributes.
- Giving decorative images verbose alt text that clutters the screen-reader experience.
Tools to detect it
Screaming Frog lists images missing alt; WAVE and axe audit accessibility; Lighthouse flags it under Accessibility.
FAQ
Do all images need alt text?
All informative images do. Purely decorative images should have an empty alt attribute.
Does alt text help rankings?
It helps image search and topical context, and it's required for accessibility — so it's worth doing well.
Related: Image & Video SEO FAQ
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Claude Vincent is a technical SEO consultant focused on crawlability, rendering, and AI-search visibility. He writes the field guides and case studies at SEO ProCheck, with a bias toward the durable, unglamorous work that decides whether search engines and AI answer engines can actually read and cite a site.
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Technical SEO consulting and GEO strategy with 20 years of enterprise experience. Case studies, resources, and tools for search and AI visibility.
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