Canonical Tag Checker
Read a page's canonical and catch the contradictions that make it ignored.
About this tool
Reads the canonical from the HTML and the HTTP Link header, then checks it against the URL that was actually served.
A canonical is a hint, not an instruction, and a contradictory one is discarded without a word. The failures worth catching are all quiet: two canonicals on one page, a canonical pointing at a URL that redirects, and a canonical combined with noindex — which asks a search engine to consolidate signals onto a page and to drop that page, in the same breath.
Common questions
Should a page canonicalise to itself?
Yes. A self-referencing canonical is the normal case and removes ambiguity when a URL is reached with tracking parameters. It is not required, but leaving it out gains nothing.
Can I canonicalise to a different domain?
Yes, and it is the correct move for syndicated content. It is also the fastest way to remove your own pages from search if pointed at the wrong host, so check the value carefully.
Why is my canonical being ignored?
Usually a contradiction: the page is in a sitemap, internally linked and canonicalised elsewhere all at once. Search engines weigh all the signals, and a lone canonical against several contrary ones loses.
Canonical or redirect?
Redirect when the duplicate should not be reachable. Canonical when both URLs must stay usable — a product in two categories, or a page with campaign parameters.