Canonical URL
A single, absolute, in-<head> <link rel="canonical"> (and/or Link header) pointing at the preferred URL. (page-parsed)
Broken variant
Five conflicting canonicals: relative, a second differing target, cross-origin, mailto:, empty href, and one in <body>.
Defect metrics
canonicalEmptyHref |
canonicalOutsideHead |
canonicalConflicting |
canonicalInvalidUrl |
canonicalRelative (info) |
canonicalCrossOrigin (info) |