Quick answer
Image sitemap extension adds image metadata.
Sitemap Image Extension
Image sitemap extension adds image metadata. Use correct namespace and structure.
Common causes
- Wrong image namespace.
- Missing image:image.
How to fix
- Use image schema; add image:image per URL.
- Validate image sitemap.
FAQ
- Image sitemap?
- Optional extension.
- Namespace?
- http://www.google.com/schemas/sitemap-image/1.1.
Fix it now
Try in validator (prefill this example)