Quick answer
An XML sitemap is a public discovery file containing canonical URLs or links to child sitemaps. NOTABIS checks whether declared and conventional sitemap locations can be fetched and parsed, then reconciles their URLs with the crawl. A sitemap is a hint for discovery, not a guarantee of indexing, ranking, or canonical selection.
What the issue means
A URL-set sitemap has a <urlset> root; an index has a <sitemapindex> root and points to other sitemap files:
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
<url><loc>https://example.com/guides/tyre-storage</loc></url>
</urlset>
Each <loc> should be an absolute URL you intend to expose. Optional <lastmod> values should describe real updates, not a timer that changes on every request. Keep private, redirected, duplicate, and non-canonical URLs out of an index meant for public pages.
Why it matters for SEO
Sitemaps provide another route for crawlers to discover important URLs, especially on large or new sites. They do not replace internal links, healthy responses, canonical signals, or useful content. A valid file can still list pages that return errors, carry noindex, or are blocked by robots rules, so content and reconciliation matter more than the file’s existence alone.
How NOTABIS detects it
NOTABIS reads Sitemap lines from robots.txt and also probes /sitemap.xml and /sitemap_index.xml. It records sitemap access after a non-error response parses as a urlset or sitemapindex with the standard namespace when supplied. Separate checks cover invalid content types, invalid namespaces, and sitemap unavailability. It stores declared URLs, duplicates, cross-origin or blocked URLs, malformed entries, and overlap with the crawl for reconciliation.
The audit is a sample with size, timeout, redirect, and safety limits. It does not prove that every child sitemap or URL was processed by a search engine.
How to check it yourself
Fetch the declared location and inspect the root, namespace, content type, and entries:
curl -sS -D - https://example.com/sitemap.xml -o sitemap.xml
head -n 10 sitemap.xml
Compare <loc> values with canonical URLs, internal links, redirects, noindex directives, and status codes. Check child indexes, file size and URL limits, XML escaping, and last-modified dates.
How to fix it
Generate sitemaps from the same source of truth as your public canonical routes. Serve XML with the standard namespace and an XML content type, split large sets with an index, and declare the final URL in robots.txt and Search Console. Remove stale, private, duplicate, blocked, or redirected entries. Fix the page response rather than expecting a sitemap to make an error page indexable.
Re-fetch the public URL from outside your office network and rerun the audit after deployment.
When this is intentional or does not need fixing
Small, well-linked sites may gain little from a sitemap. An index is an appropriate format when several child files are needed, and a site can publish specialized image or video sitemaps when those resources matter. Do not expose private URLs or add every parameter variant simply to increase coverage.
Related issues
Review sitemap access, sitemap unavailability, orphan pages, canonical URLs present, and robots.txt versus noindex. Google’s sitemap overview describes discovery and limits.
Run a NOTABIS audit
NOTABIS shows sitemap responses, validation results, and URL reconciliation so you can separate a file-format problem from a page-level crawl problem.