Discoverability · 30 points
Canonical target
One check, stated three ways: what we measure, what would make it wrong, and how to confirm it yourself.
What this measures
Where the canonical tag actually points, compared with the URL that was fetched: the page itself, another page on the same site, another host, or an http:// address on an https page. Presence alone is the canonical check's job; this one reads the destination.
Where this check can be wrong
Pointing the canonical at another URL is correct when you are consolidating duplicate versions on purpose, and this check cannot tell that apart from a mistake. A canonical added by a framework default (pointing at the homepage for every route) is a real and common defect.
Verify it without taking our word for it
curl -s https://your.site/that-page | grep -o '<link rel="canonical"[^>]*>' and compare the href with the address you requested.