This means that the URL in question has a canonical element that points to another URL, yet is included in an XML Sitemap.
Your XML Sitemap should only contain URLs you wish for search engines to index. If a URL is canonicalized, this is an explicit statement to search engines that you do NOT wish for the URL to be indexed, and instead wish for the canonical URL to consolidate indexing signals.
As such, including a canonicalized URL in a sitemap provides conflicting information to search engines, and may impact what they consider is the canonical URL, which may in turn mean that unintended URLs get indexed.
This Hint will trigger for any internal URL which has a canonical that is not self-referential, and is included in one of the submitted XML Sitemaps.
Consider the URL: https://example.com/page-a, which is included in a submitted XML Sitemap.
The Hint would trigger for this URL if it had a canonical that pointed at any other URL;
A canonical tag in the <head> which pointed at another internal URL:
<!doctype html>
<html lang="en">
<head>
<title>example</title>
<link rel="canonical" href="https://example.com/page-b" />
...
</head>
<body>...</body>
</html>
OR a canonical tag in the <head> which pointed at an external URL:
<link rel="canonical" href="https://website.com/page-a" />
OR a canonical tag in the HTTP header which pointed at any other URL:
HTTP/... 200 OK
...
Link: <https://example.com/page-b>; rel="canonical"
The current setup is technically incorrect, and may cause indexing issues.
To resolve it, you would need to do one of the following:
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