An isolated URL is one that is exclusively accessible through a canonical link reference.
Why is this important?
Such a URL lacks any internal inbound links, signifying its exclusion from the navigational hierarchy of the site, rendering it unreachable through regular browsing by users or crawlers.
Search engine crawlers can locate the page, but solely through a link with a rel="canonical" attribute. Since Page C is not linked internally, its absence from the website's internal link map ensures it remains an outlier.
Furthermore, the page doesn't receive traditional link equity as one might expect.
Canonical tags manage identical content by allowing webmasters to instruct search engines to prefer one page over others for indexing purposes. However, if the internal link patterns contradict the canonical preference, search engines might sideline the stated preference, which is sometimes the case with Google.
Often, this Optimization is activated due to an inadvertent misconfiguring of the site's settings.
What does the Optimization check?
The Optimization activates for any internal URL devoid of incoming internal links but is referenced as the canonical URL on a different internal page.
Examples that trigger this Optimization:
Consider URL: https://example.com/page-b
This URL has been assigned as canonical to another internal resource,
<link rel="canonical" href="https://example.com/page-b" />
but this canonical URL https://example.com/page-c receives no internal incoming links.
The Optimization would be triggered for URL: https://example.com/page-c
How do you resolve this issue?
A canonical URL is considered by search engines as the 'preferred URL for indexing.' If you wish for a URL to be indexed and rank well, you should direct some internal links towards it.
Oftentimes, such a URL is accidentally omitted from the main navigation structure. The remedy involves integrating the URL into the site's architecture to ensure it garners at least one internal link.
This type of issue typically requires a case-by-case strategy for resolution.