Discovery
LOWSitemap is served as UTF-8
Every fetched sitemap document decodes cleanly as UTF-8. Non-UTF-8 sitemaps are silently dropped by Search Console and trip default XML parsers used by other crawlers.
What this check looks for
sitemaps.org requires `<?xml version="1.0" encoding="UTF-8"?>` and valid UTF-8 bytes throughout the file. We inspect the raw byte stream captured by the fetcher and confirm UTF-8 decodability for every sitemap document we resolved. Any resource that decodes as another encoding (or fails to decode at all) is reported with the actual Content-Type and a header excerpt.
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
Serve every sitemap document as UTF-8
Shopify
Developer- Shopify auto-generates `/sitemap.xml` as UTF-8 — if this check fails on a Shopify storefront, you're likely on a custom proxy that re-encodes the response. Bypass the proxy or fix its content-type pass-through.
BigCommerce
Developer- BigCommerce serves `/xmlsitemap.php` as UTF-8 by default. If failing, check any CDN/edge worker rewriting the response.
WooCommerce
A few minutes- Yoast SEO and Rank Math both emit UTF-8 sitemaps. Confirm your WordPress site is configured for UTF-8 (Settings → Reading → no charset overrides).
Custom / headless
Developer- Encode the sitemap XML as UTF-8 and serve it with `Content-Type: text/xml; charset=utf-8`.
HTTP/1.1 200 OK
Content-Type: text/xml; charset=utf-8
<?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 (encoding)
The sitemaps.org protocol requires sitemap files to be UTF-8 encoded. Non-UTF-8 files are rejected by Search Console and trip default XML parsers.
Does your store pass this check?
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