URL in multiple XML Sitemaps
This means that the URL in question is included in more than one XML Sitemap.
Why is this important?
XML Sitemaps offer a clear, unambiguous way to communicate with search engines that you want a specific set of pages to be included in the index. Beyond this, they are very insightful when used in conjunction with tools like Google Search Console to understand how many of your submitted sitemap URLs are indexed.
While including URLs in multiple sitemaps is not a bad thing at all, it might obscure some of the insight you can obtain from the Google Search Console 'Sitemaps' report.
Also, URLs in multiple sitemaps may signify a mistake, and in fact some URLs are missing from sitemaps as a result.
What does the Hint check?
By default, this Hint will trigger for any internal URL which is listed in more than one XML Sitemap.
Why is this Hint marked 'Insight'?
In Sitebulb, this Hint is an 'Insight' as it does not represent an issue, and is not damaging to SEO or user experience.
However, since it might be the result of an error, or might make some reports less useful, we have notified you about it to investigate further, if you deem it necessary.
Well structured XML Sitemaps (and sitemap indexes) can be a powerful way to manage indexing (see Further Reading links below).