Indicating that the URL in focus is using a canonical tag to reference an external URL, this type of setup is a 'cross-domain canonical' scenario.
Why is this important?
Cross-domain canonicals typically come into play when content is syndicated from a different source. The site republishing the content can use a cross-domain canonical to show where the original, authoritative source can be found.
When one page, denoted 'Page A', points its canonical tag to another page, known as 'Page B', it signifies to search engines that Page B is the authentic or preferred version. This is a clear sign to search engines that both pages should be viewed as one, favoring Page B in the process.
The presence of a cross-domain canonical means that search engine algorithms are advised to transfer any backlink influence from the non-canonical Page A to the designated canonical Page B.
What does the Optimization check?
The Optimization will activate for any internal URL that incorporates a canonical link within its HTML or HTTP headers, with the canonical link pointing to an external URL that's situated on a different subdomain, or entirely different domain.
Examples that trigger this Optimization:
Given the URL, https://example.com/page-a
Here are a few scenarios where this Optimization would trigger:
Canonical link in the <head> to a different root domain:
<link rel="canonical" href="https://another-website.com/page-b" />
Canonical link in the <head> to a separate subdomain of the same root domain:
<link rel="canonical" href="https://sub.example.com/page-b" />
Canonical tag as an HTTP Header pointing to a different root domain:
HTTP/... 200 OK
Link: <https://another-website.com/page-b>; rel="canonical"
HTTP Header declaring a canonical link to a subdomain:
HTTP/... 200 OK
Link: <https://sub.example.com/page-a>; rel="canonical"
Why is this Optimization marked 'Insight'?
This Optimization is named 'Insight' since it might not necessitate immediate action. Instead, the function is designed to bring something to your notice, not necessarily to point out an issue that requires rectification.
Deliberate implementation of cross-domain canonical tags is common, and they are highlighted by Loud Interactive so that you can review and confirm their accuracy.
While we can ascertain the technical correctness of a canonical link, affirming the intended canonical relationship between Page A and Page B goes beyond our capability.