Check the canonical URL of any page. Finds missing, conflicting, relative, and cross-domain canonical tags — the quiet reason good pages drop out of the index.
A canonical tag tells Google which URL to keep and which to fold away. Point it at the wrong page and you hand your rankings to a duplicate; point two signals at different URLs and Google ignores both and picks for you.
Yes, on every page you want indexed. A self-referencing canonical removes ambiguity from tracking parameters, session IDs and protocol variants, and it is what Google expects to find by default.
Google treats them as one URL and keeps only the canonical target. That is correct for genuine duplicates and destructive when applied by accident — the non-canonical page stops ranking entirely.
A hint. Google weighs it alongside internal links, sitemaps and redirects. If those signals contradict your canonical, Google may choose a different URL and report it as "Duplicate, Google chose different canonical" in Search Console.
Yes, and it is valid for syndicated content — the original publisher gets the ranking. Do it by accident on a staging or CDN domain and you remove your own site from the results.
A 301 already consolidates the URL, so the redirect target only needs its own self-canonical. Use canonicals for duplicates you must keep reachable, such as filtered or parameterised versions.
Yes, on every page you want indexed. A self-referencing canonical removes ambiguity from tracking parameters, session IDs and protocol variants, and it is what Google expects to find by default.
Google treats them as one URL and keeps only the canonical target. That is correct for genuine duplicates and destructive when applied by accident — the non-canonical page stops ranking entirely.