Discoverability · 30 points
Canonical URL
One check, stated three ways: what we measure, what would make it wrong, and how to confirm it yourself.
What this measures
<link rel="canonical">: presence, whether it resolves, and whether it points at this page or somewhere else.
Where this check can be wrong
A correct canonical pointing at a page that later redirects still looks valid to us. And a self-referencing canonical is not required on every site — staging and preview builds point elsewhere on purpose.
Verify it without taking our word for it
curl -s https://your.site | grep -i canonical, then check the value against the URL you actually want indexed.