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SD009 – Alt Text Image Consistency

Overview

Checks image presence and consistency: DOM images should have alt text; image URLs in schema should align with DOM images (normalized URL comparison).

Probability that AI systems use this signal: Crawlers and generative AI pipelines consume structured and visible page signals for training and inference. Assessment-specific signals (e.g. schema, canonicals, trust cues) affect how likely a page is indexed and surfaced. The probability that this assessment's signal influences AI behavior is high when the page is in a product or compliance context.

Impact on geo compliance: Passing this assessment supports geo compliance by ensuring machine-readable and visible content meet standards that reduce the risk of wrong locale, pricing, or trust in AI-generated answers. Failing can lead to non-compliant or misleading surfacing.

What We Check

  • SD001 passed. Product schema image: string or list of strings (URLs).
  • DOM: all `<img>` with src and alt collected.
  • If no schema images and no DOM images: pass ("No images found - images are optional").
  • **Missing alt:** img without alt or empty alt; −50 per missing, −50 per empty.
  • **URL consistency:** schema image URLs normalized (scheme+netloc+path, lower); DOM img src normalized; count of DOM images not in schema set; −20 if any mismatch.

Pass / Fail and Score

  • **PASSED** if score >= 60.
  • **Score:** 100 minus penalties. Details: schema images count, DOM images count, missing alt, empty alt.

How to Fix When It Fails

  • Add alt text to all images for accessibility.
  • Provide meaningful alt text (not empty).
  • Ensure image URLs in schema match DOM images (normalized).

Common Issues

  • Images without alt or with empty alt.
  • Schema image list doesn’t match DOM (e.g. different order, query params, or missing images).

Dependencies

SD001. VC007 (Image Alignment) depends on SD009.

How to Verify

  • Check every <img> has non-empty alt; compare Product.image URLs to img src (after normalizing).

Additional Resources

  • schema.org Product.image: https://schema.org/Product#image
  • WCAG images: https://www.w3.org/WAI/WCAG21/Understanding/images-of-text.html