Google’s Gary Illyes said on LinkedIn this morning that you should “include the URLs that you would want to see as canonical in your sitemaps.” This is not necessarily new advice, Google has said this numerous times, but Gary had a reason to repeat this advice for some reason.
Gary added, “It’s normal to have some duplicate content on your site, but you want to give search engines as many hints as you can about which version should be canonical (I.e. shown in search results). Sitemaps is one of those hints. Not as strong as rel-canonical and definitely not even near redirects, but it can be useful still.”
So, the strongest signal is the redirect, then rel-canonical, and then sitemap file? There are probably signals in the mix, like your internal links, external links, and more.
I mean, it is logical to have your canonical URL in your sitemap. That just seems logical. But I guess Gary is seeing a lot of folks not doing this?
In 2016, John Mueller said we recommend just submitting a sitemap for the URLs that you want to have indexed, not for all variations and in 2018, he said URLs in sitemap files are used to determine the canonical URL.
So if you are serving non-canonical URLs in your sitemap file, try not to?
Forum discussion at LinkedIn.