The URL under examination operates under the HTTP protocol, however, the canonical tag specifies an HTTPS counterpart.
Why is this important?
Ensuring online security is a growing priority for search engines and marketers. It has thus become a core recommendation that all web services uniformly adopt HTTPS over HTTP. When an HTTP URL designates an HTTPS URL as the canonical version, it may disrupt search engines' ability to accurately recognize and catalog the correct URL, which in this instance, is the secure HTTPS version.
Should HTTP URLs be detectable during a site audit, yet their canonical versions point to HTTPS links, it could suggest that HTTP URLs were not intended to be discovered or crawled originally.
What does the Optimization check?
The check is triggered by any internal HTTP URL that specifies an HTTPS URL within a canonical link element in its markup.
Examples that trigger this Optimization:
If the above URL had a canonical tag pointing to an HTTPS URL, the following cases would prompt the Optimization:
Canonical link in the <head> to a HTTPS URL
<link rel="canonical" href="https://example.com/page-b" />
OR HTTP Header canonical link to a HTTPS URL
HTTP/... 200 OK...Link: <https://example.com/page-b>; rel="canonical"
How do you resolve this issue?
This issue generally points to a configuration oversight. However, there might be scenarios where canonicalization to an HTTPS URL is intentional for HTTP access points. Should this not be intentional, correction involves updating the canonical URLs from HTTPS back to HTTP. This error often emerges from particular templates or rules in your site configuration, and addressing it could resolve the issues en masse through minor adjustments to these rules or templates.
An additional line of inquiry: if the preference is for HTTPS, why were HTTP URLs accessible in the site crawl?