Discovery
MEDIUMSitemap root declares the sitemaps.org 0.9 namespace
Every fetched sitemap document declares the sitemaps.org 0.9 xmlns. Schema-validating crawlers reject sitemaps with a missing or wrong namespace.
What this check looks for
Every `<urlset>` or `<sitemapindex>` document must declare `xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"` on its root element. The check substring-matches the canonical xmlns URL against the raw XML body; missing or mistyped declarations are reported.
Which AI surfaces it affects
- Google AI Mode (UCP)60
- Microsoft Copilot50
- ChatGPT (ACP)30
- Perplexity30
- Meta AI30
Weighted against the live specs — ACP 2026-04-17, UCP 2026-04-08.
How to fix it
Add the sitemaps.org 0.9 xmlns to the root element
Shopify
Developer- Shopify's auto-generated sitemaps include the namespace by default. If this fails on Shopify, you're auditing a custom-proxy response — fix the proxy.
BigCommerce
Developer- BigCommerce's `/xmlsitemap.php` ships the namespace by default. Inspect any CDN/edge worker rewriting the body.
WooCommerce
A few minutes- Yoast / Rank Math both emit the namespace. Disable any custom sitemap-rewriting plugin if it's stripping the attribute.
Custom / headless
Developer- When you emit the sitemap, set the xmlns attribute on the root.
<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
<url><loc>https://yourdomain.com/products/blue-widget</loc></url>
</urlset>The spec it's pinned to
sitemaps.org — XML tag definitions (namespace)
The sitemaps.org schema requires the root element to declare `xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"`. Schema-validating crawlers skip documents without it.
Does your store pass this check?
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